Galileo Webchat April 10,1997
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10,
2:49PM PDT (-0700 GMT)
Testing, testing, adin, dva, trei...
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 2:50PM PDT (-0700 GMT)
No, we haven't started...I just like looking at myself typing. :-)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr
10, 2:53PM PDT (-0700 GMT)
Jo: I'm sure our enlightened audience will realize that the Dust Detector
is one of
the many instruments on Galileo.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 2:54PM PDT (-0700 GMT)
Hello inquisitive! Have you seen the new Europa images
www.jpl.nasa.gov/galileo/europa ?
Resolution down to 20 meters shows ice blocks upended, bumps
and ridges...go check it out.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 2:57PM PDT (-0700 GMT)
To inquisitive:
The new images of Europa make a very good case for there being large
amounts of liquid or mostly-liquid water near the surface in the
recent geologic past. I think that makes Europa a much better candidate
for life than we thought before. In addition, it means it's almost
certainly geologically active.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 2:59PM PDT (-0700 GMT)
Inquisitive: these are about the highest resolution out yet.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:01PM PDT (-0700 GMT)
inquisitive, at yesterday's press conference, it was stated that
the subsurface temperature of the water was in the range of 0 - 100
degrees celsius. That's a nerd joke, since that defines the
range of temperature at which liquid water can exist (aside
from changes in salinity).
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:04PM PDT (-0700 GMT)
inquisitive, There are a number of ways we might go about understanding
the subsurface temp. variations. One of the best would be to put a
lander on the surface of Europa. Or actually, several landers,
each with a device that measures the amount of heat coming out of
the ice from below.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 2:55PM PDT (-0700 GMT)
Duane is multi-talented, and the rest of us are one-trick detectors.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 2:59PM PDT (-0700 GMT)
To Andre': The data from E4 are ambiguous. They could be interpreted
(at this point) to indicate that there is magnetic field. But there are
other explanations for the data we see that seem equally good. It's going to
take some more study to be sure.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:03PM PDT (-0700 GMT)
Andre', yes, Pwyll (which rhymes with Will) can be seen in the
global view of Europa taken during the second orbit.
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:07PM PDT
(-0700 GMT)
I'm wondering if anyone from Galileo's trajectory team is on?
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:09PM PDT (-0700 GMT)
Kirk Sorensen, noone from Navigation is on yet, though someone
is scheduled to show up.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:00PM PDT (-0700 GMT)
Tom, Europa is about 1600 km in radius
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
3:05PM PDT (-0700 GMT)
Tom: Thermal imaging (which the PPR instrument does, PhotoPolarimeter
Radiometer) would only tell you about the surface layers of the planet, and
not about what the temperature is deeper than, say, a few inches. We have
to rely on indirect evidence for the center's temperature.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:08PM PDT (-0700 GMT)
-=Tom=-:, thermal imaging would tell us if there were spots that were
much warmer than the average surface. This is how the NIMS (near-
infrared mapping spectrometer) detects volcanos on Io. But if there is
a heat source in the center of the planet, it would be difficult
to detect remotely.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:08PM PDT (-0700 GMT)
Joshua Bell, the press release wording reflects geological time
scales: if we scale the age of the earth down to human lifetime
(let's make it 100 years), then the equivalent of 1 million
Earth years for a human is 8 days. I know that skin renews itself,
but not *that* quickly!
So a million year-old surface (if it's really that young) is
very very young.
: . . . . Thu, Apr 10, 3:07PM PDT (-0700 GMT)
Actually, if there are active geothermal vents on Europa a la Earth's black
smokers, there could be water superheated to temperatures > 100C near them
due to the pressure, so 0-100 might not even be enough to describe the
Ice-Lava water temperature gradient.
Orion: . . . . Thu, Apr 10, 3:08PM PDT (-0700 GMT)
I would believe there has to be convection, heat in the interior, because
of the heat caused from the pull of Jupiter. Just as the Earth is still
geologicaly active, so must all the large moons of Jupiter.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:11PM PDT (-0700 GMT)
inquisitive, we certainly don't think that Europa's water is pure.
There are likely to be many other materials and chemicals mixed
in. We just don't know what they all are, or which are important
yet.
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 3:12PM PDT (-0700 GMT)
Hi, sorry to be getting on a little late. Fabrizio, you asked about using
the main antenna. We tested it in 1991-1993. It works, but not enough
better than the low gain that the project wanted to go to the effort of
using it.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:08PM PDT (-0700 GMT)
Spectral measurements of Europa indicate that the water ice has another
component to it -- it might be a clay mineral -- but we haven't made a
positive I.D. of it yet.
jph of md: . . . . Thu, Apr 10, 3:31PM PDT (-0700 GMT)
hi io amo, you mentioned the thickness of "ice" sheet, washington post
today mentioned a range of 2/3 of a mile to 60 miless probably someone from
the team can give us more on that
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:19PM PDT (-0700 GMT)
Paul the Wall, it is amazing, isn't it, how it looks like tire tracks?
We tend to mention how it looks like the LA Freeway system.
HR>
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:12PM PDT (-0700 GMT)
Kirk, Lou D'Amario should be showing up.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:13PM PDT (-0700 GMT)
You would need to grab some geologic samples and measure radioisotopes
to narrow down the age measurements. The present age "guesses" are done
by assuming a particular influx of impactors on a given surface over time.
A variety of these models exist, the most popular one is to use that
which is based on measurements done on our moon. There we have actually
verified the dates on rocks in the lab to craters and geologic superposition
of geologic features. But, we are not sure if the same population of impactors
is hitting Europa.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:14PM PDT (-0700 GMT)
flyonwall, We can't get much better dates unless we know the
rate of crater-causing impacts in the Jupiter system better than we do
now. Looking at a surface and counting the number of craters is the
best indication we have until we get some samples of the surface
to date in labs here on Earth.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:12PM PDT (-0700 GMT)
Michael, GEM (for Galileo Europa (or Extended) Mission) is the immediate
follow on to Europa. There is talk about an Ice Clipper Mission
(lob something heavy at the surface, fly through the resulting
cloud of ice shards, grab some, fly them back to earth) and
a driller (heat the drill to melt through). But these are
all very much initial drafts of ideas.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:14PM PDT (-0700 GMT)
Io amo Io! (what a name! :-) part of NASA's mission is to
share the knowledge from each program with the public
and with students. Outreach people put together web chats
and web sites, cd-roms, posters, slide sets, curriculum
materials, postcards, you name it. I'm thinking of doing
an exercise video next :-)
Andre': . . . . Thu, Apr 10, 3:12PM PDT (-0700 GMT)
Does each instrument issue an interrupt to request sending its data
to the tape recorder when its buffer is full?
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:17PM PDT (-0700 GMT)
Andre': The onboard computer "grabs" data from the instruments and
puts it onto the tape recorder. It's a very continuous process.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:15PM PDT (-0700 GMT)
Kirk, we just got the SPICE kernels for the trajectory, but
not the ephemeri yet (which I'm assuming is what you'd
be interested in). I'll ask about it.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:17PM PDT (-0700 GMT)
Ljubo, no sign yet of an active ice geyser on Europa. Surface
dating can give an estimate of the age of features that we
think might have been formed by geyser activity.
Ljubo: . . . . Thu, Apr 10, 3:20PM PDT (-0700 GMT)
Thanks Jo!
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 3:22PM PDT (-0700 GMT)
Steve C. Hi! May I ask you a question about your computing facilities? I'd
like to know what platform do you use for trajectory and manouvers
calculations
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:27PM PDT
(-0700 GMT)
The attitude control unit uses a variety of computers for our
analysis work. We have sun workstations for telemetry display
and retrival. Most of our word processing and plotting is
done on Macintosh's, where we also have some custom written
software for things like predict generation and
star set creation and we have several pieces of OFFICIAL
software that run on an old UNIVAC that we use to
check sequences.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:15PM PDT (-0700 GMT)
Hey Hyperdude -- can you describe "hyperdimensional physics"?
Hyperdude: . . . . Thu, Apr 10, 3:19PM PDT (-0700 GMT)
From what I can gather from Hoagland (and that is difficult to do!)
"hyperdimensional physics" involve the generation of "higher order"
physics due to the spin/rotation of matter. He talks of "tetrahedral"
equations that show outflux/influx of energies at 19.5 degrees latitude
in many examples of planetary bodies, where a tetrahedron would touch
a sphere if such a sphere fully "inscribed" this tetrahedron.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:18PM PDT (-0700 GMT)
It is possible that the brown "gunk" on Europa might be organic. Us
spectral folks are working on interpreting some of the brown linea. We
are attempting to make spectral models to remove the water ice components
to see what the spectral signature of the non water ice stuff is.
Paul the Wall: . . . . Thu, Apr 10, 3:16PM PDT (-0700 GMT)
-=Tom=- : Don't you think the double ridges are tire tracks? Do you think
the CIA has only kept it's nose on earth?
-=Tom=-: . . . . Thu, Apr 10, 3:19PM PDT (-0700 GMT)
Paul the Wall, I half expect to see the ridges used in a 4X commercial.
Hey, maybe not such a bad idea.
Paul the Wall: . . . . Thu, Apr 10, 3:20PM PDT (-0700 GMT)
;-) - Thanks -=Tom=-.
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:21PM PDT (-0700 GMT)
Hi Tom, You asked about the double ridges. We think that these are due
to material "pumped" from the subsurface by repeated opening and closing
of cracks on Europa, as the moon flexes in and out under the tidal pull
of Jupiter.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:21PM PDT (-0700 GMT)
regarding the double ridges: Personally, I think these are some
of the most interesting surface features. There are probably a lot
of different ways that they could be created. Two obvious ones are (1)
pulling apart two pieces of the Europa "crust" and (2) buckling of the
crust under compressional forces.
-=Tom=-: . . . . Thu, Apr 10, 3:25PM PDT (-0700 GMT)
Thanks Paul!
Spiff: . . . . Thu, Apr 10, 3:21PM PDT (-0700 GMT)
I repeat my question to Jim Taylor : Which LGA antenna is now
in use on the spacecraft and why is the other one permanently
switched off, giving you no redudancy there ?
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
3:24PM PDT (-0700 GMT)
Spiff (question for Jim Taylor): I think one of the LGA antennas was used
before arriving at Jupiter (Venus encounter rings a bell), and perhaps it
operates at a frequency or data rate that doesn't help us now. I don't
think we're losing anything by not using it.
Spiff: . . . . Thu, Apr 10, 3:27PM PDT (-0700 GMT)
Stuart : Thanks
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 3:28PM PDT (-0700 GMT)
Spiff, sorry, I was off the Chat for a few minutes. We are operating on
low gain antenna #1 (LGA-1). So far as I know, LGA-2 would still work
perfectly. However, we aren't using it because it is pointing in the wrong
direction, away from the earth. LGA-2 was put on the spacecraft at a late
stage, when we decided to fly inbound toward Venus (as part of the
Venus-Earth-Earth gravity assist trajectory) to get us to Jupiter. LGA-2
pointed toward the earth when the spacecraft was closer to the sun than the
earth is. LGA-1 points toward the earth now. Sorry.
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . . . . Thu, Apr
10, 3:19PM PDT (-0700 GMT)
inquisitive, good question. I don't know of any way to date water ice
if it's pure. I assume that one technique would be to filter out the
silicate matter that's sure to be there, and date that with conventional
isotopic techniques. Any geochemists out there?
inquisitive: . . . . Thu, Apr 10, 3:21PM PDT (-0700 GMT)
Duane, actually I "dabble" in geochronology; and there would be no good way
to obtain an age from silicate "debris" that could potentially be
completely unrelated. Same reason why it's difficult to get absolute dates
on sediments.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:22PM PDT (-0700 GMT)
It is possible to date some "salts" if they have the right composition.
These might be able to be use as age flags. Much of Europa has a trace
(according to the spectra) of non-ice materials. And if you have silicate
volcanic smokers somewhere that might provide material for dating also.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:23PM PDT (-0700 GMT)
I almost forgot, If the surface is not being continually being resurfaced
one can use the amount of cosmic dust to date a surface as well.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:24PM PDT (-0700 GMT)
Kirk: SPICE kernels are a standardized way in which the spacecraft
trajectory can be passed between various computer programs. For
example, the people who are figuring out targeting for the
science images need to know where the spacecraft will be at
certain times.
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:18PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:21PM PDT (-0700 GMT)
Io amo Io!: . . . . Thu, Apr 10, 3:27PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:24PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:25PM PDT (-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:24PM PDT
(-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:25PM PDT (-0700 GMT)
Joshua Bell: . . . . Thu, Apr 10, 3:26PM PDT (-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:27PM PDT
(-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:27PM PDT
(-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:28PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:35PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:30PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 3:30PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 3:32PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 3:33PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:33PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:34PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:35PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:39PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:30PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:30PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:37PM PDT (-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 3:34PM PDT (-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:30PM PDT
(-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:31PM PDT
(-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:32PM PDT
(-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:35PM PDT
(-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:32PM PDT (-0700 GMT)
Fabrizio (from Italy): . . . . Thu, Apr 10, 3:30PM PDT (-0700 GMT)
Fabrizio (from Italy): . . . . Thu, Apr 10, 3:38PM PDT (-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 3:41PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:33PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:38PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:34PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:35PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:37PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:40PM PDT
(-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 3:35PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:37PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:39PM PDT (-0700 GMT)
Ed Hirst: . . . . Thu, Apr 10, 3:42PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:41PM PDT
(-0700 GMT)
Ed Hirst: . . . . Thu, Apr 10, 3:44PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:41PM PDT (-0700 GMT)
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
3:49PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:40PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:40PM PDT (-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:45PM PDT
(-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:48PM PDT
(-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 3:43PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:47PM PDT (-0700 GMT)
Paul the Wall: . . . . Thu, Apr 10, 3:44PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:44PM PDT
(-0700 GMT)
anonymous: . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:47PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:46PM PDT
(-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 3:55PM PDT (-0700 GMT)
Fabrizio (from Italy): . . . . Thu, Apr 10, 3:57PM PDT (-0700 GMT)
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
4:03PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:59PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:50PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:51PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:55PM PDT (-0700 GMT)
anonymous: . . . . Thu, Apr 10, 3:50PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 3:55PM PDT (-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:52PM PDT
(-0700 GMT)
jph of md: . . . . Thu, Apr 10, 3:53PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:52PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:49PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:51PM PDT (-0700 GMT)
jph of md: . . . . Thu, Apr 10, 3:56PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:53PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:52PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:54PM PDT
(-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:59PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:56PM PDT (-0700 GMT)
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:56PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:57PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 3:57PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 4:00PM PDT (-0700 GMT)
Daystrom: . . . . Thu, Apr 10, 3:54PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 4:02PM PDT (-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:02PM PDT
(-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 3:57PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:00PM PDT
(-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:59PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:09PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:07PM PDT (-0700 GMT)
,HR>
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:04PM PDT
(-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 4:12PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:03PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:05PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:14PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:18PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:11PM PDT (-0700 GMT)
moebius: . . . . Thu, Apr 10, 4:01PM PDT (-0700 GMT)
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 4:05PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:06PM PDT (-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:07PM PDT
(-0700 GMT)
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
4:09PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:09PM PDT (-0700 GMT)
Rebecca Westbrook, Galileo Outreach: . . . . Thu, Apr 10, 4:11PM PDT (-0700
GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:08PM PDT (-0700 GMT)
jph of md: . . . . Thu, Apr 10, 4:09PM PDT (-0700 GMT)
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
4:17PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:11PM PDT (-0700 GMT)
Muichkine from Spain: . . . . Thu, Apr 10, 4:13PM PDT (-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 4:18PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:09PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:14PM PDT (-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:12PM PDT
(-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:09PM PDT
(-0700 GMT)
Io amo Io!: . . . . Thu, Apr 10, 4:09PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:12PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:14PM PDT (-0700 GMT)
Jim Lukash: . . . . Thu, Apr 10, 4:17PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:19PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:14PM PDT
(-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:12PM PDT
(-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:18PM PDT (-0700 GMT)
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
4:40PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:17PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:14PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:20PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:21PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:20PM PDT (-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:18PM PDT
(-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:22PM PDT (-0700 GMT)
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:26PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:29PM PDT (-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:18PM PDT
(-0700 GMT)
van Gogh: . . . . Thu, Apr 10, 4:18PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:23PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:22PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:23PM PDT (-0700 GMT)
< Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:28PM PDT
(-0700 GMT)
HR>
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
4:25PM PDT (-0700 GMT)
Jim Lukash: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:32PM PDT (-0700
GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:33PM PDT (-0700 GMT)
Nancy Vandermey, Seq-Sys: . . . . Thu, Apr 10, 4:34PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:34PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:25PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
Rebecca Westbrook, Galileo Outreach: . . . . Thu, Apr 10, 4:27PM PDT (-0700
GMT)
anonymous: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
aLiEn: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:23PM PDT
(-0700 GMT)
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:24PM PDT
(-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:26PM PDT (-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
4:35PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:27PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
JK (SSI Imaging Team): . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:31PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:28PM PDT (-0700 GMT)
Muichkine from Spain: . . . . Thu, Apr 10, 4:28PM PDT (-0700 GMT)
Aso De Pacaro: . . . . Thu, Apr 10, 4:29PM PDT (-0700 GMT)
Muichkine from Spain: . . . . Thu, Apr 10, 4:32PM PDT (-0700 GMT)
JK (SSI Imaging Team): . . . . Thu, Apr 10, 4:35PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:28PM PDT
(-0700 GMT)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:31PM PDT
(-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:34PM PDT
(-0700 GMT)
Jim Lukash: . . . . Thu, Apr 10, 4:33PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:43PM PDT
(-0700 GMT)
Tim: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Aso De Pacaro: . . . . Thu, Apr 10, 4:30PM PDT (-0700 GMT)
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:34PM PDT (-0700 GMT)
Aso De Pacaro: . . . . Thu, Apr 10, 4:32PM PDT (-0700 GMT)
aLiEn: . . . . Thu, Apr 10, 4:34PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:33PM PDT (-0700 GMT)
aLiEn: . . . . Thu, Apr 10, 4:35PM PDT (-0700 GMT)
espaŅol: . . . . Thu, Apr 10, 4:35PM PDT (-0700 GMT)
Edward Hirst: . . . . Thu, Apr 10, 4:36PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:35PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:37PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:36PM PDT (-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 4:54PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:39PM PDT (-0700 GMT)
Tim: . . . . Thu, Apr 10, 4:39PM PDT (-0700 GMT)
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:40PM PDT
(-0700 GMT)
Jim Taylor, Galileo radio: . . . . Thu, Apr 10, 4:45PM PDT (-0700 GMT)
Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 4:41PM PDT (-0700 GMT)
JK (SSI Imaging Team): . . . . Thu, Apr 10, 4:41PM PDT (-0700 GMT)
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:43PM PDT (-0700 GMT)
Jo, or anyone else: Are there any follow-up missions to Jupiter in the
serious planning stages yet? E.g., a balloon or blimp floating around
Jupiter's atmosphere, or a sailplane or some such thing.
Io amo Io!, I'm not aware of any serious planning of follow-up
missions, but yes, the balloon concept is under general study
(more for Venus right now). The probe people, esp., would
like a Jovian balloon mission.
Andre': . . . . Thu, Apr 10, 3:19PM PDT (-0700 GMT)
When will the images of the small moons be released? I know
one of Amalthea was released from the G2 orbit, but when will the
others be posted?
Andre', don't know when images of the small moons will next be
released. Sorry.
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:19PM PDT
(-0700 GMT)
Test
Io amo Io!: . . . . Thu, Apr 10, 3:20PM PDT (-0700 GMT)
Anyone out there, Galileo team member or visitor, who can answer a simple
question about photoelectric cells? The question is: Since Jupiter
radiates very strongly in the radio wave frequencies, is there a substance
that we can use to build a "Jovian cell" to power a flyer or balloon in
Jupiter's atmosphere? Just expose it downward, toward Jupiter, and you've
got all sorts of power. Can such a thing be done? (Sorry, I guess that's
actually TWO questions...)
Any takers on my photoelectric cell question? Or do I have to do it the
hard way and look it up myself?
Joshua Bell: . . . . Thu, Apr 10, 3:21PM PDT (-0700 GMT)
Serious question: assuming that the floating ice chunks are really floating
ice chunks (embedded in much thinner ice), any theories as to what opened
up the large surface region so that they could flow into it? Sublimation of
surrounding ice "continents" below others? Large impact that
shattered/melted part of the crust (and thus didn't leave a crater)?
Hi Joshua, You asked what could have opened Europa's surface so that the
"ice bergs" could float. About the only thing that could cause melting of
Europa's
surface on this scale is heating from below, perhaps due to volcanism
in the silicates at the floor of the liquid layer.
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
3:22PM PDT (-0700 GMT)
Jo: Are the GEM trajectory "petal plot" and other key info (like encounter
dates) available to folks outside of JPL? I know the trajectory to Io was
only selected recently. [Relates to Kirk's question.]
Stuart: the GEM trajectory "petal plot" (so named because
it resembles a flower) and the other traj. info hasn't been
posted yet. I'd assume it will be up and available in (wild
guess here) the next two months.
GeorgGeorr: . . . . Thu, Apr 10, 3:23PM PDT (-0700 GMT)
Did A. C. Clarke discuss the possibility of life in the liquid water oceans
of Europa in one of his novels? The heat for the melting of the ice would
come from subterranean (subEuropean?)tidal forces generated by Jupitor's
gravitational pull.
GeorgGeorg: AC Clarke discussed life on Europa in 2010, published in 1981.
A Chinese mission landed on Europa to refuel and was attacked by the
indiginous lifeforms.
GeorgGeorr -- check out 2010 (the book) where a Chinese spacecraft
gets dragged into Europa by a light seeking creature.
Speaking of ACC/2010, if we ever do identify species native to Europa,
we'll have to name one of them after the Chinese explorer who made the
radio report in 2010.
-=Tom=-: . . . . Thu, Apr 10, 3:26PM PDT (-0700 GMT)
Does anyone remember the end of 2011?
==Tom==: Jupiter becomes a star. Go figure.
Stuart Stephens, Ultraviolet Spectrometer Team, JPL: . . . . Thu, Apr 10,
3:26PM PDT (-0700 GMT)
Hi Paul! I enjoyed the press conference
yesterday. What did your T-shirt say? (It looked like "Club
Europa"...)
I liked Paul's T-shirt too--where can I get one?
Hi Stuart, Thanks. The t-shirt read "Club Europa - good ice fishing and
langlaufen" and was made by Jeff Moore at NASA/Ames.
Andre': . . . . Thu, Apr 10, 3:26PM PDT (-0700 GMT)
Has anything new been discovered about Europa's thin oxygen
atmosphere?
ryan: . . . . Thu, Apr 10, 3:27PM PDT (-0700 GMT)
does anyone know if there is a chance that the substance in its liquid
state is anything besides water?
ryan - Most of that frozen surface on Europa has a STRONG spectral
signature of H2O ice.
Tim: . . . . Thu, Apr 10, 3:27PM PDT (-0700 GMT)
Is it possible that the ice bergs could have flowed from an impact
that melted the surface in that area?
Tim: It seems possible to me that an impact might have *triggered*
volcanism. But at other places where we've seen cratering, there isn't
enough melting from the impact alone to completely obliderate the crater.
Messier: . . . . Thu, Apr 10, 3:27PM PDT (-0700 GMT)
Is this finding of "H2O ICE" a 100% discovery? Are you absolutely sure it
is this solid?
Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:28PM PDT (-0700 GMT)
For those who asked about the contamination of the water with
other material, organic and otherwise, Rich Terrile said at
yesterday's press conference that "The water is bouillion, but we don't
know yet if it's chicken soup"
desde EspaŅa: . . . . Thu, Apr 10, 3:28PM PDT (-0700 GMT)
Por casualidad ųalguien habla en espaŅol?
Esto debe estar muy interesante, lastima que no entienda perfectamente el
ingles...
esperare un poco haber si alguien me contesta en espaŅol...
esperando... (waiting)
epanol: solamente hablo un poco de espanol. Lo siento. Hay
una scientist que habla espanol, pero ella no esta aqui.
momento...
espanhol - no se si puedo "translate" todo esto.
espaŅol, translate = traducir.
rowemm: . . . . Thu, Apr 10, 3:28PM PDT (-0700 GMT)
What can we infer about the thickness of the ice from looking at
Pwill crater? Nature conveniently provided us with a probe!
Hi rowemm, Pwyll is indeed a good probe of the interior of Europa. The depth of
the crater floor is only about 100-200 m below the rim. For comparison, a
young crater
of similar diameter (26 km) on Ganymede would be over 2 km deep.
Joshua Bell: . . . . Thu, Apr 10, 3:28PM PDT (-0700 GMT)
Re: "ice bergs" - I can probably check for myself, but where on the surface
of Europa is the region with the "ice bergs"? Anywhere near the (whatever
you call the point perpetually nearest Jupiter) ?
Joshua Bell, the ice rafts/bergs mentioned yesterday are found
in a region in the northern hemisphere right under what's
referred to as "the Big X" (two lineae prominently intersecting--
you can't miss it in the global images of Europa)
Joshua Bell and yes, that point is on the Jupiter-pointing side
of Europa
Hi Joshua, the ice bergs occur at a point about 90 degrees away from Jupiter,
near the equator. This is where the ice is expected to be thinnest.
Spiff: . . . . Thu, Apr 10, 3:29PM PDT (-0700 GMT)
Steve Collins : I don't know exactly if the following is an attitude
question but apparently there are no CDS Power On Resets anymore
(fortunately). Is this slip-ring debris problem solved or are we just
lucky ?
Spiff, I saw and answered your second question about LGA-2 first. (That's
OK, I'm often accused of doing things backwards and being built upside
down.) You also asked if LGA-2 had any different characteristics to help
communications. No, both of them operate at exactly the same frequency and
(when we have accounted for cable losses), have about the same gain. To
use LGA-2, we would have to redeploy it (it's on an arm that was folded
back in prior to Probe release), and then command a switch to it. The
moment that happened, we'd be out of communications because it points away
from the earth now.
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 3:29PM PDT
(-0700 GMT)
Hello: I'm signing on.
Lou: I'm so glad you're here. I tried to write you an email this morning
but it didn't work.
Kirk: What can I do for you?
Lou: I'm working on a Uranus trajectory for a design we're doing, and I
read about your work in JGC on Galileo. I'm wondering about the PLATO
software you used--is there any way to get access to it?
Kirk: PLATO has been replaced by two newer programs (depending on accuracy
requirements): MIDAS and CATO. There is a policy on release of JPL
software. It just can't be given out freely. I would suggest calling Dennis
Byrnes (818-354-3030). He is the Group Supervisor of the Outer Planets
Mission Analysis Group and would know about the software release
guidelines.
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 3:29PM PDT (-0700 GMT)
Steve C. Thanks! What is your official language/toolkit for the development
of your custom software?
Hyperdude: . . . . Thu, Apr 10, 3:30PM PDT (-0700 GMT)
Hoagland by the way is setting himself up to make a "big announcement"
on the ART BELL program next week. I wonder if it will have anything
to do with Europa. Also, you know he thinks that NASA (which rumoured
to be run now by some intelligence agency) is covering up something.
He also thinks you can receive secret messages from Masonic Orders
and the Opus Dei by dialing 1-800-OLD-NAVY.
Hyperdude - That's Old Navy clothing company !?! That's in Chula Vista, CA.
And didn't I say somehting about the CIA four-wheeling on Europa?
Fabrizio (from Italy): . . . . Thu, Apr 10, 3:15PM PDT (-0700 GMT)
Thanks Jim.
So the antenna works, even if with a lower gain.
Could it be possible to use the omnidirectional one and the other in
a small array mode?
For Jim Taylor. You said that high gain antenna works, even if with a lower
gain.
Could it be possible to use the omnidirectional one and the high
gain in array mode?
For Jim Taylor. You said that high gain antenna works, even if with a lower
gain. Could it be possible to use the omnidirectional one and the high gain
in array
mode?
Fabrizio, that was a good question about whether we could consider
"arraying" the high gain antenna with LGA-1. No. In the future, when our
on-board subsystems are more programmable, that kind of imaginative
capability might be considered. For now, we have a simple pair of
commands. One is "select HGA" and the other is "select LGA". Also, when I
said the HGA was working (somewhat), I meant at X-band. We did consider
operating a dual downlink, X-band over the HGA and S-band over the LGA. We
didn't have enough power to do that *and* run the science instruments.
Also, pointing the HGA accurately toward the earth would have been very
difficult to achieve. That's because, with the HGA partly opened, we ended
up with many smaller lobes in the pattern instead of one nice big main
lobe. The highest power of the lobes wasn't on axis. Sigh....
ryan: . . . . Thu, Apr 10, 3:31PM PDT (-0700 GMT)
why is it liquid h20 and not ch4? or even something else? isn't it cold out there?
Ryan, Europa is not cold enough for liquid/frozen methane. For those
temperatures you need to go farther from the sun, like Triton.
Joshua Bell: . . . . Thu, Apr 10, 3:32PM PDT (-0700 GMT)
Total tangent: if any of the Galileo team members (listening or otherwise)
are ex-Pioneer 10 team members, congratulations on bringing that amazing
mission to a close. That mission made Voyager and Galileo both possible, so
all of this amazing stuff we're seeing and learning now is really thanks to
them.
anonymous: . . . . Thu, Apr 10, 3:32PM PDT (-0700 GMT)
A message that I received from Reuters says that a "red-colored sea"
was observed on Europa. On the other hand, what liquid water exists
would be below the surface. If the water is below the surface, how
could it be seen as a "red-colored sea"?
regarding "red" Europa: the new reports are referring to the red color
seen in some images of Europa. This is not what Europa really looks like to
our eyes. It's the result of enhancements done to the images to make
subtle features clear to scientists (and, well, also because it looks cool).
Someone at the press conf. yesterday noted that the "red" stuff would
appear dark brown to our eyes.
Andre': . . . . Thu, Apr 10, 3:32PM PDT (-0700 GMT)
Will the GEM include observations of Jupiter and Io?
Andre' -- GEM will include Io Observations and I think some Jupiter observations
at a lesser priority. GEM's primary targets are Europa and Io.
Andre', GEM will focus on Europa initially, then a few flybys
of Callisto (to pump the orbit down to get to Io), and then
the possibility of two Io flybys at the end. Actually getting
Io data back to Earth depends heavily on the health of the
spacecraft at that point. There will be some Jupiter
observations.
bushman: . . . . Thu, Apr 10, 3:33PM PDT (-0700 GMT)
this is cool!!!!
ryan: . . . . Thu, Apr 10, 3:33PM PDT (-0700 GMT)
perhaps iron oxides pollute the water? or maybe it's not water.
ryan - from the models and measurements I have seen the temperatures on
the surface are around 130 -110 Kelvin, a little too warm for exotic
liquids.
Spiff: . . . . Thu, Apr 10, 3:34PM PDT (-0700 GMT)
Lou D'Amario : I read you stopped taking OPNAV pictures because
the orbits of the moons are know very well known. I guess that's
true for the Galilean Moons. How about the small ones ?
Spiff: We don't normally take OPNAV pictures of the small satellites of
Jupiter, becuase improving their ephemerides is not necessary for
navigation purposes (i. e., we don't come close to them, and even if we
did, there would be no significant gravity-assist effect). Howevere,
several OPNAV pictures were taken of Adrastea in order to improve its
ephemeris for science imaging purposes.
Rich vanH: . . . . Thu, Apr 10, 3:34PM PDT (-0700 GMT)
What is the current temperature of Europa's surface?
Edward Hirst: . . . . Thu, Apr 10, 3:34PM PDT (-0700 GMT)
Hola! 'espan~ol' Podria repetir su pregunta? Gracias!
se sabe la temperatura que puede haber bajo la capa de hielo de Europa?
espaŅol, no me acuerdo la temperatura. Ya se me fue.
espaŅol, James Granahan dijo que la temperatura sera por 110 a 130
Kelvin.
'Espanol' - Todavia no se sabe la temperatura del agua que hay debajo
de la capa de hielo de Europa. Puede estar a temperaturas desde
0 grados C a 100 grados C. Lo mas probable es que no se va poder
determinar la temperatura hasta que se mande un "lander" a la
superficie de Europa.
ryan: . . . . Thu, Apr 10, 3:35PM PDT (-0700 GMT)
james, what are the temperatures out there on the surface of europa, and
underneath, if known?
Hyperdude: . . . . Thu, Apr 10, 3:35PM PDT (-0700 GMT)
As Richard C. Hoagland says now "STEADY AS SHE GOES!".
He is really into oceans now, since he believes all secret societies
were based in ancient mariner colonies.
Buggs: . . . . Thu, Apr 10, 3:36PM PDT (-0700 GMT)
On the page 'Europa Ice Rafts' one crustal plate seems to be 'tipped over'
could it be that the hill on page 'Europa Triple Band' in the center of the
picture
is such a tipped over crustal plate ... an one edge stick out ??
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:36PM PDT
(-0700 GMT)
Lou: I wrote Dennis this morning. If PLATO has been superceded, will it
be available publicly anytime soon?
Kirk: I don't know. In any case, running PLATO took a lot of training. I
would try to get a copy of MIDAS (a simpler, easier-to-use program).
bushman: . . . . Thu, Apr 10, 3:36PM PDT (-0700 GMT)
is it very cold on Europa?
espaŅol: . . . . Thu, Apr 10, 3:37PM PDT (-0700 GMT)
Hola Duane ! Estoy contento de que alguien me entienda, a que se dedica
usted?
'Espanol' - Duane le manda decir que el es un cientifico planetario.
ryan: . . . . Thu, Apr 10, 3:37PM PDT (-0700 GMT)
makes sense. what kind of spectrometers are used to detect the
elements/compounds that far way?
LW: . . . . Thu, Apr 10, 3:37PM PDT (-0700 GMT)
Hello! I was wondering how you came to the conclusion that Europa has
water under the surface. Is it just based on images and spectra readings
or something? Also, what did you use to determine the minerals or
compounds in Europa?
L.W. -- the water under the surface evidence can be argued from a
variety of data. I believe that the press conference primarily used
imagery of landforms which suggest liquid water. Gravity measurements
can also be used to argue about liquid water. Most people use spectroscopy
to positively identify compounds on Europa.
Andre': . . . . Thu, Apr 10, 3:38PM PDT (-0700 GMT)
Would an ocean of water be detected conclusively if changes are
noticed on the surface of Europa?
Michael: . . . . Thu, Apr 10, 3:38PM PDT (-0700 GMT)
What is the composition of the atmosphere of Europa? Is it a thin
atmosphere?
In response to questions about Europa's atmosphere, here are a couple of
excerpts from journal papers in the last two years:
Europa's molecular oxygen atmosphere is very tenuous, with a
surface pressure about 10(-11) that of the Earth's atmosphere at
sea level. [10(-11) = 1 part in 100 billion.]
Here we report the discovery of an atmosphere of atomic
sodium that extends to at least 25 times Europa's radius. We suggest that
this sodium is originally released by Io's volcanoes, after which it is
ionized in the magnetosphere and implanted into Europa's surface ice;
subsequent sputtering of the ice by magnetospheric ions releases the sodium
to form the extended atmosphere.
Georgeorr: . . . . Thu, Apr 10, 3:38PM PDT (-0700 GMT)
Re: Liquid water, 0-100 C. Here in Boulder water boils at ca. 95 C. With
such a thin atmosphere, and such a small mass, why didn't Europa lose the
water to space long ago? What am I forgetting?
Georgeorr: some of the water will boil away, but some will
freeze. That's what keeps it from all sublimating away.
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:39PM PDT
(-0700 GMT)
It's been quite a while since we had a despun bus reset.
I believe we still see DC bus imbalance shifts that
make us believe that the problem has not "gone away" but
we've not had a bad enough short to cause a POR.
We've got all the files we need "on the shelf" to
bring the spacecraft back up promptly if one occurs.
espaŅol: . . . . Thu, Apr 10, 3:39PM PDT (-0700 GMT)
Son ustedes de verdad los cientificos a cargo de la Galileo? Seria
fantastico !
espaŅol, algumos son los cientificos, y algunos solo tienen interesa.
Spiff: . . . . Thu, Apr 10, 3:40PM PDT (-0700 GMT)
Steve Collins : Doesn't the asymmetric deployed HGA give you
a disturbing wobble in the spacecraft spin-axis ? If yes, does
it matter and how do you correct science/engineering data for it ?
The HGA configuration does effect the spacecraft mass properties.
We have actuators on each of the RTG booms that allow us to move
the RTGs and compensate the wobble caused by the funny HGA.
This is one of the ways we know that that HGA did not change
configuration during orbit insertion. If the HGA was to come
open, it would change the spacecraft mass properties and
we could see the increased wobble in spacecraft telemetry.
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 3:40PM PDT (-0700 GMT)
What are the language/toolkit that you use for your internal software?
The Attitude control software is programmed in a language
called HAL/S and also uses some machine language subroutines
for things like interrupt handlers. HAL/s is also used in some of the
Shuttle flight
software. It's a lot like Fortran.
ryan: . . . . Thu, Apr 10, 3:41PM PDT (-0700 GMT)
kelvin is celcius plus 273.15 or something right? if so, wouldn't 130K be
too cold? perhaps my scale is off...
Lynae: . . . . Thu, Apr 10, 3:41PM PDT (-0700 GMT)
James G., any possibiliby of getting a web posting of the STRONG spectral
signals?
I am a teacher in MN and we were just learning about spectra and how to use
it yesterday. My students would like it!
Paul the Wall: . . . . Thu, Apr 10, 3:41PM PDT (-0700 GMT)
espaŅol, de donde vienes. EspaŅa?
Paul: soy de Valencia-EspaŅa-Europa. Y tu de donde?
espaŅol: Como que no! Soy the San Diego, California, USA.
espaŅol: Soy originalmente the Mar del Plata, Argentina. Pero ahora, lo
siento, pero tengo que hirme. Chau!
espaŅol: . . . . Thu, Apr 10, 3:41PM PDT (-0700 GMT)
Paul: de 110 a 130 Kelvin, perdona mi ignorancia pero no recuerdo la
equivalencia a grados Centigrados...
espaŅol: De kelvin a centigrados se suma -273,15
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:42PM PDT
(-0700 GMT)
Lou: And Dennis would be the person to ask about getting a copy of
MIDAS?
Kirk: Try him first. He can direct you to the appropriate person. (Also,
Carl Sauer developed MIDAS - you might want to give him a call
(818-354-4875).
jph of md: . . . . Thu, Apr 10, 3:42PM PDT (-0700 GMT)
Paul G; you mentioned volcanism as a possible cause for the opening of the
surface; what about radiation from Jupiter heating this material under the
surface, or is that considered the same thing as "volcanism?"
Hi jph of md, Actually Jupiter does provide the energy, but by tidal
heating rather than radiation.
anonymous: . . . . Thu, Apr 10, 3:43PM PDT (-0700 GMT)
D.R. Cosaert ( from: the Netherlands)
This is like the " X-Files" !!! Good Luck and hopely you find what you
want.
Buggs: . . . . Thu, Apr 10, 3:44PM PDT (-0700 GMT)
Is there a way to check out how thick the icy crust is ?
Bryan in Kansas: . . . . Thu, Apr 10, 3:44PM PDT (-0700 GMT)
Greetings from Topeka. During the GEM Io flyby, what would be the
spacecraft systems most subceptable to damage by radiation? If the
science instuments fail, is it likely that you would still be able to
transmit back whatever information had been collected up to that time?
Bryan in Kansas: computer memory is fairly susceptible to
radiation damage. If the science instruments fail...well,
that assumes that they *all* fail at the same time. More
likely that only one would die at a time.
LW: . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
I remember reading something about iceflows or frozen rivers possibly
caused by fluid below rushing to the surface on the surface of Europa on
your web site. If a probe were launched to Europa to detect life or
organic compounds, wouldn't taking samples from these work, instead of
drilling into the surface to get below?
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:45PM PDT
(-0700 GMT)
Lou: Thanks a ton. You're great--I've read about five of your papers and
really admire your work.
Kirk: Thanks for the compliment.
Fabrizio (from Italy): . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
Jim Taylor : which are the gains of LGA and of undeployed HGA?
Fabrizio, LGA-1 has a gain of about 8 dBi, on axis, for the S-band downlink
frequency. That unit dBi means decibels relative to a isotropic antenna (a
uniform pattern in all directions). I can tell you what the HGA gain would
have been if it deployed. It would have been 50 dBi at the X-band downlink
and about 36 dBi at S-band. I no longer remember what we figured the gain
was for the partly deployed HGA. I only remember that we thought the
overall performance (X-band HGA compared to S-band LGA-1) was somewhere
between 1 and 2 dB. While that's significant, so was the complexity.We
picked up our 1-2 dB and a lot more with improvements in the spacecraft
(with data compression and a new error correcting code) and the stations
(arraying several ground antennas together and operating the main one in an
ultra low noise mode, called "ultracone").
Jim Taylor : Thanks a lot.
Jack: . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
Hi, What's the latest on Ganymede's ice tectonics??
John: . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
James Granahan: What about that magnetic field on one of jupiters moons,
can you say there is positively something there?
ryan: . . . . Thu, Apr 10, 3:45PM PDT (-0700 GMT)
james, has anyone speculated on what type of life might exist out there?
obviously thermophiles may exist near those ocean vents, but could anything
more exotic be out there?
Buggs: . . . . Thu, Apr 10, 3:46PM PDT (-0700 GMT)
And how deep are the chunks between the (big) ridges ?
Andre': . . . . Thu, Apr 10, 3:46PM PDT (-0700 GMT)
Has an atmosphere been detected on Callisto?
Andre', about Callisto's atmosphere: I'm not aware of any definitive
observation of an atmosphere around the outermost Galilean satellite. But,
I'm noticing that there has been speculation about cometary impacts leading
to thin atmospheres (from theoretical modeling). Also, I see the
statement, "The dark material on Callisto's surface may be a remnant of an
earlier, now vanished atmosphere" (1995 Journal of Geophysical Research
paper). The Ultraviolet Spectrometer on Galileo has been taking spectra at
atomic oxygen and hydrogen wavelengths (1304 and 1215 Angstroms) to look
for material in the orbits of Callisto and Ganymede that may be associated
with thin atmospheres.
Muichkine from Spain: . . . . Thu, Apr 10, 3:46PM PDT (-0700 GMT)
Hello! To everyone: What do you think about the tubes, chanels, or... ?
That appears practically in all the images... That kind of structures
seems OVER the surface when campare with crevases shadows...
So far as I know, the NIMS team efforts have been to provide infrared
imagery and ratios and not the weird squiggly lines which are spectra.
That might change in the future when publications become closer to
completion.
anonymous: . . . . Thu, Apr 10, 3:46PM PDT (-0700 GMT)
What is tidal heating?
anonymous, tidal heating is when tidal forces (in this
case, tidal forces caused by Jupiter acting on Europa)
heat something by friction. The tidal force tugs on the
interior back and forth (for Io, these tidal forces are
fairly dramatic, even for solid material), which causes heating.
You can model this by bending a paper clip back and forth, and
then feeling how the metal near the bend heats up.
anonymous: Tidal heating is caused by gravitational forces acting on
(in this case) the moons of Jupiter. If the orbit of a satellite is
anything other than a perfect circle, the changes in gravitational force
actually stretch the body. When you flex solid material that way, it
causes frictional heating. (that's the$.05 explanation, anyway)
Hi anonymous, tidal heating is caused by friction as Europa is squeezed
in and out each Europan "day" (3.6 Earth days). Because it isn't in a
circular orbit aroud Jupiter, it is sometimes closer to Jupiter and
sometimes farther away. As it gets closer, the tidal bulges grow (by an
amount that depends on how deep the subsurface ocean is) and as it gets
farther away, they subside. Friction during this process heats the interior.
The extreme example is Io, where tidal heating produces the most geologically
active body in the solar system.
anonymous: . . . . Thu, Apr 10, 3:47PM PDT (-0700 GMT)
From: D.R. Cosaert ( the Netherlands)
To: D.R. de Haan ( the Netherlands)
Je weet niet wat je mist ! Dit is best wel grappig!
All the best!!!!
From: D.R. Cosaert
To: D.R. de Haan
He, kan je me even een 'S'-rapportje geven? Zit momenteel met een straal
verbinding te zenden, gericht op Mother Earth! Met maar 10mW ! Gaaf he?
espaŅol: . . . . Thu, Apr 10, 3:47PM PDT (-0700 GMT)
Ed Hirst: Estupendo, tenemos un rango de temperatura adecuado,
solo faltaria que existiesen compuestos organicos lo suficientemente
complejos como para que exista la posibilidad de vida. Efectivamente
para saberlo habra que bajar alli; cosa mas dificil.
espanol: Ya hay ingenieros que estan planificando y disenado varios
tipos de sondas que podrian ir a Europa (algun dia) y aterizar en
la superficie. Algunos solo se quedarian en la superficie, pero otros
llevarian una fuente de calor y, deritiendo la capa de hielo, se
hundirian bajo ella. La dificultad seria en controlar que tanto se
meten a la capa de hielo, pues muy hondo y no podrian transmitir
sus datos.
ryan: . . . . Thu, Apr 10, 3:47PM PDT (-0700 GMT)
let's assume there is liquid water out there. is it salt water? and if
so, is there any evidence to suggest potassium or lithium salts or anything
else interesting?
Arthur Toy: . . . . Thu, Apr 10, 3:48PM PDT (-0700 GMT)
Hello from Paw Paw, Michigan. Will you be able to post the spectral data in
graphical form on a web site?
Spiff: . . . . Thu, Apr 10, 3:48PM PDT (-0700 GMT)
Steve Collins :Is the orbital tour a "busy" period for attitude people,
i.e. are there a lot of attitude changes ?
SPIFF: It's been fairly quiet. There's some sequence development,
we change attitude a few times an orbit, and do a few maneuvers to
keep us on the trajectory. Things do get exciting occasionally
as happened over the weekend when we had a star processing
anomaly just before the encounter.
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 3:48PM PDT
(-0700 GMT)
I was talking to some engineers in SoCal who are working on a solar power
system for a Europa orbiter. Can anybody comment on the record on when we
might hear some more about that?
jph of md: . . . . Thu, Apr 10, 3:48PM PDT (-0700 GMT)
A question about space and not about Jupiter ( with apologies). Is there a
such thing as "up" or "down" in space? i.e. does space appear to have a
direction or a handedness to it?. Having seen the tail of Hale-Bopp, there
appears to be a fainter, second tail above the primary, brighter tail, as
the second tail appears to be "above" the first tail doesn't this imply
that whatever constituents are in that tail are "lighter" than those in the
primary tail so they appear above the primary tail. Just had to throw this
in.
A question about space and not about Jupiter ( with apologies). Is there a
such thing as "up" or "down" in space? i.e. does space appear to have a
direction or a handedness to it?. Having seen the tail of Hale-Bopp, there
appears to be a fainter, second tail above the primary, brighter tail, as
the second tail appears to be "above" the first tail doesn't this imply
that whatever constituents are in that tail are "lighter" than those in the
primary tail so they appear above the primary tail. Just had to throw this
in.
jph of md, no, there is no up or down in space. The two tails
of the comet that you mention are a dust tail, and an ion
tail (comprised of ionized material). Both of them point in the
direction away from the sun, and not in the direction "behind"
the comet's direction of travel. They separate because they
interact differently with the solar wind.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 3:49PM PDT (-0700 GMT)
There has been a positive detection of an intrinsic magnetic field at
Ganymede -- courtesy of the magnetometer team.
Hi Buggs, these ice bergs give us an estimate of Europa's crustal
thickness - just like ice cubes in water float with 10% of their thickness
above the water surface, the ice bergs' height (100-200m) suggests
Europa's crust was only 1 - 2 km thick at the time they were formed.
Tim: . . . . Thu, Apr 10, 3:49PM PDT (-0700 GMT)
If there is life in europa would jupitors magnetic field have any
effect on it(since its protected by the ice)?
Tim, based on terrestial lifeforms, like bacteria, life might evolve
on Europa to navigate/orient themselves with respect to Jupiter using
the magnetic field.
B.: . . . . Thu, Apr 10, 3:50PM PDT (-0700 GMT)
Why the great variation in the height of double ridges (tire tracks)?
Do they get lower with age..? Do they grow gradually with time, how
fast?
Superficial Sally: . . . . Thu, Apr 10, 3:50PM PDT (-0700 GMT)
jph: If you were to stand on your head in space, down would be up, and up
down!
Dear sally; that's not exactly what I had in mind. if "down" was
essentially the same as "up" why would one of the tails of Hale Bopp appear
to be above the other? Why wouldn't they both fan equally in the same
direction?
Daystrom: . . . . Thu, Apr 10, 3:50PM PDT (-0700 GMT)
Can Galileo (eventually) detect the existence of magnetic field generated
by Jupiter moons?
Daystrom: Galileo has detected an instrinsic magnetic field at
Ganymede. There is some very interesting data at both Io and Europa,
but discussion is still going on as to what the data mean. Callisto
probably does not have its own magnetic field.
Daystrom -- It already has at Ganymede.
Spiff: . . . . Thu, Apr 10, 3:51PM PDT (-0700 GMT)
Lou : Now that the moon ephemerides are well-know, do you need
less or smaller OTM's or are they mainly caused by errors in
spacecraft position/burn precisions ?
Spiff: Basically what you said is correct. We don't schedule any fewer
OTMs, but the estimates of their sizes (and hence total tour propellant
consumtion) have gone down. This is what has provided the propellant to do
the two-year follow-on GEM mission.
Nancy Vandermey, Seq-Sys: . . . . Thu, Apr 10, 3:51PM PDT (-0700 GMT)
about radiation effects - several instruments have had 'bit flips' in their
software, which happen at Jupiter closest approach, where the radiation is
highest. We have had to reload their memory.
espaŅol: . . . . Thu, Apr 10, 3:51PM PDT (-0700 GMT)
Esos compuestos organicos podrian existir en caso de colisiones
de cometas con Europa, me equivoco?
Muichkine from Spain: . . . . Thu, Apr 10, 3:52PM PDT (-0700 GMT)
Paul: I was working in remote sensing over polar areas with several
types of sensors... and if Europa has ice shells its dynamics is
very disimilar than ice shells on earth... What do you think about?...
Hi Muichkine from Spain, we're still puzzling over the dynamics of ice
on Europa. It is likely to be more similar to that of ice shelves than
glaciers.
Michael Rigby, Utah State University: . . . . Thu, Apr 10, 3:52PM PDT
(-0700 GMT)
What kind of clamping mechanism was used to hold in the atmospheric
probe?
Michael Rigby: are you referring to what held the descent module
(i.e. the science instruments) inside the aeroshell (which
absorbed the brunt of the atmospheric entrance) or to
something else? I believe it was bolts that held the aeroshell togheter;
those were blown off, allowing the descent module to fly
free.
Bryan in Kansas: . . . . Thu, Apr 10, 3:53PM PDT (-0700 GMT)
I know that the GEM is going to be operated on a reduced annual budget.
What would you do with more money, assuming you had it, that you won't
be able to do with the upcoming budget?
Bryan in Kansas -- If GEM was funded at the present levels it would increase
the data return to Earth and the amount of observations that GEM could
take. It would also keep the engineers around to react to surprises and
scientists to rapidly analyze and prepare data products at the present
level of effort. I suspect that I will be looking for a different job
at the nominal end of this mission.
nontechnical-minded: . . . . Thu, Apr 10, 3:53PM PDT (-0700 GMT)
How is Europa heated by the gravity of jupiter and the other moons?
nontechnical-minded: tidal heating (see other messages) is what
heats Europa and Io's interiors.
ryan: . . . . Thu, Apr 10, 3:53PM PDT (-0700 GMT)
james, how are magnetic fields generated?
About magnetic fields: (If you don't mind, James) The best idea we have is
that magnetic fields occur in planets if they have a convecting layer made
up of conducting material. Convection is what hot liquid (or near-liquid)
materials do to transport heat from the interior of a planet toward
its colder outer portions. More to come...
About mag. fields: The convecting material has to be a conductor so
it can carry electrical current. Electrical currents generate magnetic
fields, which in turn help to maintain the current. The idea is that
if such a system gets the proper kick to start it off, you have a
self-generating dynamo. The energy source is whatever heat is driving
convection. (continued...)
James G. Area the any theory about the source of the magnetic field on
Ganymede?
James G. -- Sorry. Typing error. Are there any theory about the source of
the magnetic field on Ganymede?
about mag. fields: In Ganymede, the best candidate for a source of the
magnetic field is a molten iron layer, similar to the Earth's outer
core. In Jupiter, the mag. field is thought to arise in a layer of
metallic hydrogen.
Steve Collins : About the star maps, early in the mission these were
changed now and then. When was the currently used star map
loaded in the orbiter ? Do they still need the be changed ?
Spiff: On galileo, each change of attitude requires us
to update the onboard "star set". Unlike Cassini and more modern
spacecraft, Galileo attitude determination uses only 2 to 6 stars
and we have to pic the ones that are in the slice of sky that
the star sensor sweeps out. We were able to restore attitude
accuracy over the weekend (before the encounter!) by changing
one of the stars in our "star set" to one in a different part of the
sky. (WHEW!)
espaŅol: . . . . Thu, Apr 10, 3:54PM PDT (-0700 GMT)
Exacto, alguien pregunta por ahi si es cierto que el hielo de Europa es
de agua (H2O), esta esto comprobado? tiene algun otro componente detectado
a parte del agua?
Exacto, alguien pregunta por ahi si es cierto que el hielo de Europa es
de agua (H2O), esta esto comprobado? tiene algun otro componente detectado
a parte del agua?
espanol: Se sabe que el hielo de Europa es de agua por los calculos
que se han hecho de la densidad de Europa. Es possible calcular la
densidad de Europa por medio de medidas que se han hecho de la
gravedad alrededor de Europa. Se especula que el hielo esta mezclado
con una variedad de elementos - organicos y otros, pero no se ha
comprobado la existencia.
-=Tom=-: . . . . Thu, Apr 10, 3:56PM PDT (-0700 GMT)
Considering the size of many of Jovian moons, is there any evidence of moon
satilites or "moon moons"?
Spiff: . . . . Thu, Apr 10, 3:57PM PDT (-0700 GMT)
Lou D'Amario : Can you give a typical deltaV or propellant
usage for an OTM early in the tour or now ?
Spiff: There are 3 OTMs per orbit: usually 3 days before and after an
encounter and at apojove. The pre-encounter OTMs are typically a few tenths
to a meter per sec. The post-encounter OTMs vary from a meter per sec or
less up to several meters per sec. At one time, we thought they might be as
large as 10 m/s. The apojove OTMs are generally small: meter per sec or
less, with a few exceptions - i. e. , the apojove OTMs that have
detrministic comoponents.
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 3:57PM PDT
(-0700 GMT)
The probe was held on by 3 clever explosive bolt mechanisms.
They are designed to hold the probe securely and then release
the probe when fired electrically. I believe they each have 2 charges
and will still release even if one charge fails to fire.
The probe is then pushed away from the orbiter by springs.
There is also a pyro activated "cable cutter" that chops
the wire bundle between orbiter and probe before probe
release.
Aso De Pacaro: . . . . Thu, Apr 10, 3:57PM PDT (-0700 GMT)
Do neutrinos go through Jupiter, or are they trapped by the massive amount
of matter?
Aso De Pacaro: neutrinos should still pass through Jupiter.
Keep in mind that they pass through the Sun, which is much
more massive than Juptier
moebius: . . . . Thu, Apr 10, 3:58PM PDT (-0700 GMT)
how can europa generate a magnetic field?
Michael Rigby, Utah State University: . . . . Thu, Apr 10, 3:58PM PDT
(-0700 GMT)
I'm wondering about the actual bolts that held the probe to the orbiter.
Would anyone know the power requirements to blow the bolts?
Vincent de Jager, the Netherlands: . . . . Thu, Apr 10, 3:59PM PDT (-0700
GMT)
Hello everyone... I was wondering, if the atmosphere around Europa is
so thin wouldn't the ice sublimate into space?? And if so could that
explain why Europa appears to be so young (the surface seems to be
smooth)?
Hi Vincent de Jager, Sublimation probably does occur on all of these
icy satellites, but Europa's surface is definately less cratered than
that of Ganymede and Callisto (which are darker and should sublimate
faster).
J: . . . . Thu, Apr 10, 3:59PM PDT (-0700 GMT)
How thick is the ice layer on Europa thought to be and what does this mean
for any possible probe missions?
Muichkine from Spain: . . . . Thu, Apr 10, 3:59PM PDT (-0700 GMT)
Could someone explain the hypothesis and data to conclude that Europa ice
sheet is similar to earth ice sheets?
Hi Muichkine, I meant the dynamics are more similar to ice sheets (i.e.,
brittle failure in a thin shell) than to glaciers (ductile flow).
Buggs: . . . . Thu, Apr 10, 4:00PM PDT (-0700 GMT)
Paul: could there now be any places of liquid water by tidal heating
directly on the surface ?
Hi Buggs, Europa's surface is COLD (-150 C) so there could be no liquid water
there. We think there is liquid below the surface due to tidal heating.
James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr
10, 4:00PM PDT (-0700 GMT)
Aloha folks, I have to get back to other tasks and some appointments.
Catch ya at the next chat.
LW: . . . . Thu, Apr 10, 4:00PM PDT (-0700 GMT)
Are there frozen rivers on Europa's surface caused by eruptions of fluid
inside Europa? If so, then wouln't these be an easier place for a sample
of the fluid under the crust?
Aso De Pacaro: . . . . Thu, Apr 10, 4:00PM PDT (-0700 GMT)
How do we KNOW that neutrinos pass through the sun? How can we detect
neutrinos that come from the sun and neutrinos that come from behind it?
Spiff: . . . . Thu, Apr 10, 4:01PM PDT (-0700 GMT)
Steve Collins : About the Galileo thrusters. Do you still use all
Z, S, L and P thrusters and is there still need for "flushing" ?
Spiff: All our thrusters are still working and we still do regular
thruster flushes every few weeks.
Spiff, I can concur that we do thruster flushes every few weeks. The
ground radio receiving system is so sensitive that it is affected by the
*unmodeled* doppler caused by the flushing of the Z-axis thrusters! The
change in the spacecraft generated S-band downlink frequency caused by each
pair of Z-thrusters is 0.25 Hz. That's 0.25 Hz out of a total of
2,295,000,000 Hz. Recent thruster flushes have knocked the downlink
receiver out of lock momentarily. The NAV folks are trying to model the
timing of the flushes better, a work very much in progress.
espaŅol: . . . . Thu, Apr 10, 4:01PM PDT (-0700 GMT)
Edward, la solucion podria ser: al llegar a la superficie se ancla una
antena sobre ella unida a un cable hasta la sonda. La sonda se hunde
y va desplegando el cable por el que transmite los datos hasta la
antena. Podria ser?
Si no por un cable, por radio desde el interior del agujero hasta la antena
anclada en la superficie...
Edward: que opinas? seria posible?
espanol: perdon por el atrazo.. las ideas de las sondas para la
superficie de Europa son excellentes y effectivamente algunas de
las ideas que se estan estudiando.
Edward: ok, si me necesitais estoy dispuesto a unirme al equipo de
diseŅo de la Nasa :-)
Daystrom: . . . . Thu, Apr 10, 4:01PM PDT (-0700 GMT)
Duane - Was the Ganymede mag field expected or was it a "surprise" ?
faciovi: . . . . Thu, Apr 10, 4:01PM PDT (-0700 GMT)
hola porque el color de jupiter es rojo
faciovi: Sulfur compounds in Jupiter's atmosphere give it
that red color.
faciovi: Los colores en la atmosfera de Jupiter son evidencia
de los procesos quimicos que estan occuriendo. Algunos cientificos
creen que el color rojo es debido a la precencia de fosforo, otros
creen que es debido a la precencia de compuestos organicos.
moebius: . . . . Thu, Apr 10, 3:59PM PDT (-0700 GMT)
duane, could molten iron transport the heat on europa?
james or duane, is it known what is on the inside of europa? i mean, under
the layer of liquid water...
moebius: There is probably both rocky material (silicates) and
metallic iron (possibly with some sulfur mixed in) in the interior of
Europa. Both of these would have to transport at least some heat. But whether
they do so by conduction, or convection, or by melting and being transported
as magma, we don't know yet.
Bryan in Kansas: . . . . Thu, Apr 10, 4:02PM PDT (-0700 GMT)
Back in the eighties, some private individuals contributed money to
keep the Viking Mars lander going. Has anyone thought of setting up a
similar fund for Galileo to suppliment federal funding? I'll certainly
contribute to it!
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:04PM PDT
(-0700 GMT)
I don't know the pyro initiator currents, but they are fired
by a capacitor bank that we charge off of the RTGs
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
Duane - Can you please explain me how the mechanism you described works
("The idea is that if such a system gets the proper kick to start it off,
you have a self-generating dynamo"). I can't understand how the system
maintain a current.
Aso De Pacaro: . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
Duane: Yes, but since satellites don't have a axis of spin, how can they
generate a magnetic field?
moebius: . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
DUANE! metallic hydrogen? that's amazing? I don't understand the
difference between hydrogen and metallic hydrogen.
moebius: metallic hydrogen is hydrogen that's ionized: it's essentially
protons (hydrogen nuclei) floating in a sea of electrons. It's
highly conductive, hence its name. Normal hydrogen, with
neutral charge, doesn't conduct.
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:05PM PDT
(-0700 GMT)
Going offline for 5 min.
Spiff: . . . . Thu, Apr 10, 4:05PM PDT (-0700 GMT)
Steve Collins : (Sorry to have two subjects simultanous). This star
set updates, are they real up-links or just instructions in the
sequence using a large "star data base" on board ?
SPiff: on Galileo, we actually send the Ra and Dec of each star
we want up to the spacecraft in the star set. We don't
have a "full sky" catalog like Cassini et al. The darned
computer's too small!
anonymous: . . . . Thu, Apr 10, 4:05PM PDT (-0700 GMT)
Stuart: Thanks. What you said about Callisto is interesting. That
reminds me: what is the latest word about ozone on Ganymede?
Duane, Kent suggested your name for driving the van home tonight!
anonymous: I believe ozone has been positively identified on Gaynemede, and
I confess I should know for sure since I believe UVS has seen it in our
Ganymede data.
faciovi: . . . . Thu, Apr 10, 4:05PM PDT (-0700 GMT)
Galileo regresa a la tierra? Cuando?
faciovi: la Galileo no regresara a la Tierra, no puede, ademas no
tendria ningun sentido.
facoivi, Galileo no regresa a la tierra sino permanecera a Jupiter.
(No hablo espanol...)
ToddSaintPe': . . . . Thu, Apr 10, 4:06PM PDT (-0700 GMT)
I'm looking at PIA005~6. There are two circular areas. One smooth (I
understand due to welling up of subterrainian fluids, the other is rough.
What would explain such wildly divergent terrain in such a local place.
They both seem to be in responce to subterrainian stimuli. Any ideas?
ToddSaintPe': one theory I've heard is that the wildly different
types of terrain adjacent to each other indicates that there
was a hot spot under one region, but not the other. I don't
understand why there is such a sharply divergent line between
the two regions. I suspect the satellites people are puzzled,
too.
Superficial Sally: . . . . Thu, Apr 10, 4:06PM PDT (-0700 GMT)
jph: If you want them fanning equally in the same direction, why no tilt
your head sideways?
Dear sally; that's not exactly what I had in mind. if "down" was
essentially the same as "up" why would one of the tails of Hale Bopp appear
to be above the other? Why wouldn't they both fan equally in the same
direction?
Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . .
. . Thu, Apr 10, 4:07PM PDT (-0700 GMT)
yeow. Sorry folks, but I've got to run -- got a vanpool to catch.
Will try to log in from
home around 5:30. Sorry to duck out...can you save your questions?
Andre': . . . . Thu, Apr 10, 4:07PM PDT (-0700 GMT)
Stuart: Thanks. What you said about Callisto is interesting. That
reminds me: what is the latest word about ozone on Ganymede?
about ozone on Ganymede: HST (Hubble Space Telescope) observed ozone
absorption at 2600 Angstroms in 1996 (KS Noll et al., Science). It is
thought that the combination of molecular oxygen (O2) and ozone (O3) that
is observed is in some combined form that is not actually a gas atmosphere,
but rather represents molecules trapped in near-surface ice. This would be
what causes the absorptions. The Ultraviolet Spectrometer (UVS) on Galileo
confirms these observations at similar wavelengths.
Muichkine from Spain: . . . . Thu, Apr 10, 4:08PM PDT (-0700 GMT)
Edward: Aparentemente la dinamica de esa presunta capa de hielo es
similar, al menos en cuanto a fragmentaciŪn, a la de los
casquetes de hielo continentales... pero aparecen estructuras
extraŅas ... que hipotesis barajais para explicarlo?
Muichkine: quizas cristalizaciŪn por la diferencia de temperaturas?
EspaŅol: No lo se... Pero como se explica que las estructuras
lineales que aparecen presenten relieve sobre el casquete... parecen
flujos de algo no colisiones entre placas de hielo...
Spiff: . . . . Thu, Apr 10, 4:08PM PDT (-0700 GMT)
Jim Taylor : Do you use the same Bit Error Rates as for example
used on Voyager? I would guess that these things are not very mission
dependent ?
Spiff, you asked about our bit error rate, as compared with Voyager. No,
they're not the same, at least not any more. Voyager and Galileo (up to
the time of the use of the new on-board 'Phase 2' software last year)
required a bit error rate no worse than 1/200. The error rate is a
function of the received signal power. Galileo Phase 2 has a formal error
rate requirement of 1 part in 10 million. We translated this to mean the
loss of about one frame of telemetry data in the rest of the prime mission.
Alas, we lose more than 1 frame per day, but not because of bit error rate
issues. Thruster flushes, for example, as I wrote before.
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:08PM PDT
(-0700 GMT)
I guess there's no official word on a Europa mission, eh?
Kirk Sorensen: only on GEM, nothing else.
Tim: . . . . Thu, Apr 10, 4:08PM PDT (-0700 GMT)
Is it possible that the core of europa is spinning at a different rate
than the rest of the planet? This would make the possibility of a global
ocean more likely.
Hi Tim, We think it is likely that Europa is rotating nonsynchronously
(turning slowly when viewed from Jupiter, unlike Earth's Moon, which
always faces the same way). This is based on the reorientation of fractures/
ridges on its surface. If we learn that the interior is locked to Jupiter,
then it would require that the crust is decoupled from the core.
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:08PM PDT (-0700 GMT)
Steve Collins - Can you please tell us some numbers about the spacecraft
computer (memory. mips, etc).
Silvio: The attitude control processor has about 128k of ram and
is a 286 class processor (but with built in floating point) The
CDS is really a bunch of small integer processor modules with
some ram (don't know how much...) on each. Tal? You out there?
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:09PM PDT
(-0700 GMT)
I am back.
Lou: I'm glad you're back.
Io amo Io!: . . . . Thu, Apr 10, 3:58PM PDT (-0700 GMT)
Hi, folks. Got kicked off the phone for a few minutes, so now I have a
question: If Io is so tectonically/volcanically active from its interior
being molten due (ostensibly) to the gravitational effect of Jupiter, and
if there's some iron compounds in Io (which there must be)...why haven't we
detected a magnetic field around Io? Why is Ganymede so special that
way?
Duane Bindschadler: If Ganymede has this great, big magnetic field, why
wouldn't Io? It certainly has all sorts of energy input in the form of
gravitational deformation, and its overall composition surely must include
iron, nickel, and/or other conductors.
Io amo Io!: There may be a magnetic field around Io: it hasn't been
definitively detected yet. This is something of a controversy
right now, and is one of the reasons why the magnetometer team
wants to do another Io flyby.
pc: . . . . Thu, Apr 10, 4:10PM PDT (-0700 GMT)
Hello to all, and thanks to the team for taking the time to do this!
The news is exciting! What percentage of what satellites will be
imaged at the end of the (two year extenstion of the) mission?
How long will Galileo remain in Jovian orbit?
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:11PM PDT
(-0700 GMT)
Will there be any imaging of the beyond-Callisto satellites?
Jim Lukash: . . . . Thu, Apr 10, 4:11PM PDT (-0700 GMT)
Curiosity Question: Considering the icy surface "Seals" the planet, is it
possible that many of the dissolved "Volatile" compounds that would
normally outgass on a low gravity world may actually remain trapped within
the ocean on europa?
I would imagine any "Breaks" in the ice seal over rather quickly, so
outgassing would be a time-limited event. The reason I ask is that if
dissolved gasses exist trapped inthe oceans of Europa, I would imagine it
might be more hospitable to life.
Jim Lukash: this was exactly one of the points made at the press
conference yesterday: it's certainly possible that there is
an enrichment of organic material under Europa's crust.
Thanks Jo (Jo Pitesky, Galileo Outreach:) I was unable to see all of the
conference (Some of us work for a living). I wanted to thank the whole
team of folks for taking the time to do this with the general public.(Heck,
even those of us who work in the space industry learn about current events
from this).
B.: . . . . Thu, Apr 10, 4:11PM PDT (-0700 GMT)
GEISSLER, SSI: Could you elaborate on the formation of double ridges,
('tire tracks')?
How long do they take to form? Forming by liquid from below?
Hi B., About the double ridges: we don't know how long they take to form,
but we can make some back-of-the-envelope calculations assuming that the
tidal strain is taken up by a few discrete fractures, and that some fixed
fraction of their volume reaches the surface during each flexing cycle. It
appears
possible to build ridges on a short time scale ( a few tens of thousands
of years) but, as with all geophysical modelling, the answer depends on
your assumptions.
Spiff: . . . . Thu, Apr 10, 4:12PM PDT (-0700 GMT)
Lou D'Amario : In the spacecraft trajectory model for the orbital tour,
are there still important non-gravitational forces to account for ?
Spiff: We take into account solar pressure, velocity impulses from both
thruster flushing activities and unbalanced spacecraft turns. Solar
pressure is very important for the larger orbits.
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:11PM PDT
(-0700 GMT)
Kirk: Dennis tells me that it is next to impossible to release JPL
trajectory design software, but someone could make a specific run for you.
That's what has been done for other students working on the same project
you are involved in.
Lou: That would be great. How long does that take?
LW: . . . . Thu, Apr 10, 4:12PM PDT (-0700 GMT)
Hello again! I was wondering if anyone answered my question a while back
about Europa and frozen rivers. Thanks
Bryan in Kansas: . . . . Thu, Apr 10, 4:13PM PDT (-0700 GMT)
During the GEM Io flyby, will you be repeating the observations that
were planned for December 95, or have you come up with a whole new set?
Byran in Kansas: GEM will use new plans for observing Io, not
a repeat of '95 (though the science goals are the same).
Aso De Pacaro: . . . . Thu, Apr 10, 4:13PM PDT (-0700 GMT)
I want separate streams for the chat protocol!
Andre': . . . . Thu, Apr 10, 4:13PM PDT (-0700 GMT)
Jim: Do you know what the celestial mechanics team has learned about
the interior of Callisto?
Andre' (I think) asked about Callisto's interior some time ago.... I
believe the Radio Science team was able to get useful constraints on the
degree to which Callisto's core is separated from its mantle/crust, from C3
Callisto-flyby data. But I'm forgetting the result.... Was it that
Callisto appeared to have very little density variation (i.e., like a
sphere that has the same density throughout)? Anyone else remember? I
think they didn't expect to learn much from that encounter because it
wasn't that close to the satellite, but I think they did get something (we
may learn more after the C9 and C10 Callisto encounters).
ToddSaintPe': . . . . Thu, Apr 10, 4:14PM PDT (-0700 GMT)
Jo, I would understand the hotspot causing the smooth surface, but given
that it is relatively near the other area what would cause the rougher
surface of that circular area?
Todd, I suspect that the hot spot causes the ice to break up,
so that would be the indication of the hot spot. OTOH, the
bumps that are noted (the circular areas) could also be signatures
of hot spots. I know this sounds contradictory, which just shows
that all of the science analysis is just beginning.
espaŅol: . . . . Thu, Apr 10, 4:07PM PDT (-0700 GMT)
Edward: dime algo de la idea para el lander de Europa...
Repito la idea del lander: el vehiculo se posa sobre la superficie y
desplega una antena que queda anclada al hielo. Luego la sonda se
hunde en la capa por calor, y por medio de un cable unido a la antena
o por radiotransmision se comunican los datos para ser enviados a
la Tierra. Quizas sea ridicula la idea...
waiting...
espanol: No es ridicula la idea. Es muy buena, lo que hay que
considerar es que hay que transportar todo ese equipo de la tierra
hasta la superficie de Europa... incluyendo todo el cable. Si la
capa de hielo de Europa es muchos kilometros de profunda, te imaginas
cuanto cable hay que llevar, y cuanto pesara? Un transmisor en la
sonda y otro en el lander no requiere tanto cable, pero en ese caso
se trata de poder transmitir atravez del hielo o se corre el riesgo
que el hueco se cierre detras de la sonda.... que piensas?
Io amo Io!: . . . . Thu, Apr 10, 4:14PM PDT (-0700 GMT)
Jo: Thanks. Obviously, I'm confused. I had thought that the initial Io
flyby showed *NO* magnetic field. Was there some question as to the
reliability of this data, or am I misremembering?
Io amo Io!: I don't think the data was unreliable, just inconclusive.
Duane has gone home, so I don't know if the problem was spatial
or temporal (time) resolution.
Spiff: . . . . Thu, Apr 10, 4:15PM PDT (-0700 GMT)
Jim Taylor : Isn't it great to see almost everything the s/c does with
your downlink ! The fact that your receiver has been knocked out
of lock, is this due to the fact that you don't use a carrier frequency
anymore (or do you ?)
You're really up on our communications system, Spiff. No, we don't
generally transmit a carrier now. The receiving system restores the
carrier from the data sidebands, to allow demodulation to proceed. Thus,
the ground system has a carrier tracking loop in operation, even though we
don't transmit a carrier. We learned in preparing for the 1995 solar
conjunction (radio path passing close to the limb of the sun), that we
would do better against the solar plasma effects if we transmitted a
carrier. There is always something new to learn, something new to try in
spacecraft communications!
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:15PM PDT (-0700 GMT)
Steve Collins - Interesting! Is the 286 CPU a commercial version or is it a
special version developed for interplanetary environment?
Silvio: Sorry I think I left the wrong impression. We use a custom
processor NOT a 286. The performance is something like a 286
running at a few megahertz.
Silvio: y encima correra con Windows 3.1 !!! :-D
EspaŅol - Windows non puedes funcionar sobre um 286! ;-)<=BR CLEAR left>
Silvio: me equivoque, pero si con Windows 3.0 ...
Aso De Pacaro: . . . . Thu, Apr 10, 4:15PM PDT (-0700 GMT)
Now I remember the question I've always wanted to ask!
*** Where can I get recordings of plasma wave sounds from planetary flybys? ***
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:17PM PDT
(-0700 GMT)
Kirk: What is the command that one uses to query someone's email
address?
Lou: You send a message to query@jpl.nasa.gov with the person's name as
the text of the message.
van Gogh: . . . . Thu, Apr 10, 4:04PM PDT (-0700 GMT)
Has anybody made an estimate on the kind of ocean pressures that any living
organism would have to endure on Europa?
Any estimates on what kind of ocean pressures any possible living
organism would have to endure?
van Gogh: no specific idea on the pressure, but keep in
mind that there is sea life down in the trenches of
Earth's Pacific basin. So high pressure is not enough to
rule out life.
ToddSaintPe': . . . . Thu, Apr 10, 4:19PM PDT (-0700 GMT)
Jo, to continue my thought: Underwater hotspots on earth are usually
accompanied by chains of islands/or othe tell tale chains. This crust is
obviously moving. Why wouldn't we see such cles here?
Todd SaintPe': we have chains of islands here following hotspots
because of plate tectonics. But Europa doesn't have moving
crustal plates, so the hot spot would not change location. Compare to
the gigantic volcanoes on Mars, which are huge because the
vent doesn't move around, allowing Olympus Mons to build up.
Robert Sterling: . . . . Thu, Apr 10, 4:19PM PDT (-0700 GMT)
I'm curious about the statements from the conference that suggest the ice
may be as little as three feet thick -- wouldn't tidal forces rip it to
shreds? Europa's orbiting Jupiter, after all.
Hi Robert Sterling, Mike Carr noted that a layer of ice three feet thick
would form IMMEDIATELY
when liquid water reaches the surface (did you see Total Recall? :-).
After that, it would freeze by thermal conduction, rapidly at first and
more slowly later on.
Spiff: . . . . Thu, Apr 10, 4:19PM PDT (-0700 GMT)
Lou D'Amario : Do you know the current propellant margin of Galileo ?
And with what confidence can the GEM be completed with this current PM ?
Spiff: The current PM (90% confidence) to the end of the prime mission is
~50 kg (that includes the 20 kg bookkept as Project Manager Reserves). The
PM to the end of GEM (the second of two Io encounters) is ~9 kg. I believe
the probability of completing GEM (from a propellant point of view) is
>95%.
Io amo Io!: . . . . Thu, Apr 10, 4:20PM PDT (-0700 GMT)
All this talk about Ganymedean ozone has got me wondering: What are the
opinions of the folks at NASA and JPL regarding the Antarctic "ozone hole"?
Is there a consensus opinion? It seems to me that the very best,
brightest scientists are continually surprised at incoming data and find
themselves remodelling like mad when (for example) a magnetic field is
detected around Ganymede. Given a hugely complex system like the Earth's
atmosphere, and the fact that we've only been observing a part of it
(ozone) for less than 20 years, doesn't it seem rather ridiculous to run
around shouting "The sky is falling!" when there's a variation in ozone
levels?
Or is this too far off-base for this chat? If so, I withdraw the
question.
Io amo Io: I'm inclined to agree with you. There are other (e.g., solar)
influences that may affect global climate, and data for longer time-frames
can help tell us which influences are the most important.
Jim Lukash: . . . . Thu, Apr 10, 4:21PM PDT (-0700 GMT)
A Truely dumb question follows. Topic: The long range life of Galileo.
You folks know the main trajectory, planned course changes, etc. What is
the current "End of mission" plan for this probe? Will there be any
"unique" ending, like Magellan's terminal Aerobraking experiment?
I do not wish to abuse this privilege, but I'll politely repeat my question
once more. What is the current "End of Mission" scenario/date?
Jim: The end-of-mission date for the prime mission is 12/7/97.
Jim Lukash, end of mission is now end of GEM, which will be in
Dec of 1999, assuming the spacecraft is still functioning.
Eventually, the s/c will 1) crash into Jupiter (most likely),
2) crash onto one of the satellites, or (least likely) 3)
be flung out into interplanetary space.
Jim - re: end of mission: GEM has 8 Europa encounters, then 4 Calisto
encounters to lower the perijove, then 1-2 Io encounters, at which time
Galileo will either be fried from radiation, out of power, or out of nav
fuel. Plus, it will be December 1999, and our sequence computers can't
handle the year 2000. (Seriously!)
Jim Lukash: The Galileo prime mission will end in December of this
year. NASA has approved a 2 yr follow-on mission called the Galileo
Europa Mission... it will end 7 December 1999.
Aso De Pacaro: . . . . Thu, Apr 10, 4:21PM PDT (-0700 GMT)
espaŅol, Edward: How do you create the 'Ņ' character, besides
cutting-and-pasting I mean?
espanol: lo de la n~... no se, la verdad es que no me preocupo mucho
por la n~ o por tildes... pero, se me ha dicho que es aceptable usar
n~...
Edward: Mmmmm... a ver si se me ocurre algo...
KenKong: . . . . Thu, Apr 10, 4:22PM PDT (-0700 GMT)
Great job! Does anyone know the density of Europa?
KenKong, Europa's density is about 3 g/cc
Hi KenKong, Europa's density is abou 3 g/cm?3.
aLiEn: . . . . Thu, Apr 10, 4:22PM PDT (-0700 GMT)
hello, im kinda late, any1 else here because they are doing extra credit
for their science class?
aLiEn: What kind of class are you doing extra credit for?
Rebecca: well, im 13, so im in junior high, for a science class
sorry, that was me rebbeca, forgot to put my name :o)
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:23PM PDT
(-0700 GMT)
Nah, most of us are just Galileo nuts!
Kirk: Thanks.
Silvio U. Zanzi (Italy): . . . . Thu, Apr 10, 4:23PM PDT (-0700 GMT)
A question about trajectory calculation. It will probably sound stupid but
it's my curiosity since I was 8 years old! How can the spacecraft cross the
asteroids belt safetly from small material fragments?
Silvio: Even in the asteroid belt, there's lots of room between
things. That's why they call it "space"...
Silvio: Lou may have more to say about this, but most of
the asteroid belt is empty space, not like something out of
the scene in Star Wars where the Millenium Falcon flies into
the remains of an exploded planet. Galileo had two flybys of
asteroids, and we actually had to *detour* to get near them.
There is some danger, but it's not as great as it would seem.
Silvio U, the questions left over from being 8 years old are the best. The
answer to how Galileo got through the asteroid belt safely is that there is
a lot more empty space than there are particles. I remember sitting in a
Galileo review in the mid-80s in which your very question was asked.
Someone came up with an answer that the chances of Galileo being damaged
was about one part in a million. (They could have made up that number for
all I know, just being a radio guy.)
Jo Pitesky and Steve Collins - Ok but I always tought that inside the
asteroid belt there is a high probability to hit very small fragment, not
easily detectable on Earth ground observations. I always tought wrong!
Thank you for your explanation!
anonymous: . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
Hello. This is John Keller (JK for short). I'm a graduate student
working on Galileo's Imaging Team with Clark Chapman in Boulder, Colorado.
We've been working mostly on surface features on the icy moons of
Jupiter (Europa/Ganymede/Callisto) and doing crater counts to try to
get a better fix on relative ages of the surfaces of these moon's
surfaces. As a first year grad student, I'm not really an expert on
any of this yet, but I'm more than willing to try to answer any
questions.
Andre': . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
How's the tape recorder doing?
About end-of-GEM scenarios: I don't think they're talking about going into
Jupiter's atmosphere or crashing onto one of the moons or anything like
that. I think they want to try to use it as fully as possible before the
money runs out. E.g., the philosophy is to "use the tape recorder until it
breaks" (although obviously they take great pains to be very careful in
doing so!). Maybe they'll run out of fuel first, maybe the central
computer will fail, etc. (I don't think power degrades before other limits
come into play). Anyone else have thoughts...?
Spiff: . . . . Thu, Apr 10, 4:24PM PDT (-0700 GMT)
Jo Pitesky : Did I look over it or are the post-encounter trajectory
results of orbits 4 and subsequent not posted anymore ? Any reason ?
I appreciated them very much !
Spiff, are you asking about updates to the ephemerides?
Mick B: . . . . Thu, Apr 10, 4:25PM PDT (-0700 GMT)
On a scale of 1 to 10, how likely is it that there is a liquid water
ocean under the surface of Europa? Does any other description fit the
surface observations as well as the liquid ocean scenario? What can be
speculated about the thickness of the solid surface layer?
Mick B: It's pretty much a 10 that there WAS, at some point, liquid
water under the surface. But none can answer with any assurance
yet if there is liquid water there right now.
Mick B - Based upon all the movement we see on Europa's surface,
it appears VERY likely that the water underneath it's icy shell is
liquid. It is still not proven, of course, and there is still talk
that some of the traction for movement could be caused by ice under
very high pressures with some sort of solid state convection going on.
However, the opinion at the press conference was that only a liquid
ocean is going to cause the type of uplifted blocks we've seen.
Hi Mick B, I'd give it a 9! There is a possibility that convection in
warm (but solid) ice could produce Europa's surface features, but at the moment,
I couldn't tell you how. The main elements of the ice berg observations are
rotation, translation (sideways motion) and tilting. These are easy to
accomplish if they're floating in a fluid, difficult otherwise. Based
on their heights (and minimum widths), we guess the ice bergs were 1 - 2
km thick at the time they were formed.
Aso De Pacaro: . . . . Thu, Apr 10, 4:26PM PDT (-0700 GMT)
Edward: and what do you do about accent marks (')?
Aso: los teclados en Spain llevan la - a la derecha de la L.
van Gogh: . . . . Thu, Apr 10, 4:26PM PDT (-0700 GMT)
Paul, what about ocean pressures on Europa?
Spiff: . . . . Thu, Apr 10, 4:27PM PDT (-0700 GMT)
Jim Taylor : Yes, I find interplanetary spacecraft communications
very interesting and it must be very challenging too, especially on
Galileo !!
Aso De Pacaro: . . . . Thu, Apr 10, 4:27PM PDT (-0700 GMT)
Muichkine from Spain: How did you do it!
With the keyboard spanish configuration of course!
Muichkine from Spain: you must show me. Reference?
De Pacaro: Es una opciŪn de comfiguraciŪn...
Tim: . . . . Thu, Apr 10, 4:28PM PDT (-0700 GMT)
Hi JK: what is the latest latest estimate on how old the surface of
europa is?
Tim - Europa definitely has one of the youngest surfaces in our solar
system. There are simply very very few craters on its surface.
Something has gone on very recently to flood the surface of Europa
and destroy any past impacts that have hit its surface. Clark gave
an estimate at yesterday's press conference of 1 million years old
for the ice flow regions shown. Even if he's off by a factor of 10
or 100, 100 million years is still very young compared to the fact that
the moon has been here for 4500 million years.
Kirk Sorensen, Utah State University: . . . . Thu, Apr 10, 4:21PM PDT
(-0700 GMT)
Lou: Why is it so hard to get old trajectory software? On the COSMIC page
it says that NASA is under mandate to release it to the public in a timely
manner....
Kirk: I think I missed an earlier question. Can you repeat it?
Lou: I'm surprised that it is so hard to get software. On the COSMIC
page, it says that NASA is under mandate to release its software to the
public in a timely manner....
Kirk: I know about COSMIC. There was quite an effort a few years ago here
to define a s/w release policy. Prior to that, there was no policy. The
current JPL pilicy may conflict with what COSMIC says. I'm really not an
expert in this area.
Dear Kirk Sorensen, Utah State University: Let me try to answer, based upon
my experience in the industry(I'm Not JPL). . . . Kindly realize trajectory
software has many uses, some of which are not exactly peaceful. I am sure
gulf war veterans are happy the software is not readily available.
Io amo Io!: . . . . Thu, Apr 10, 4:29PM PDT (-0700 GMT)
Tante grazie, everyone. I've gotta sign off, but I'll download and read
the chat later on. Thanks for the great info.
Spiff: . . . . Thu, Apr 10, 4:29PM PDT (-0700 GMT)
Jo Pitesky : To be more precise : After G1 and so there was a
posting of the effect of the encounter on the trajectory. Things like
total deltaV, errors, exact closest approach distances etc. Prepared
by the NAV team, so maybe I can ask Lou.
Spiff: Because of perturbations caused by errors in the last flyby (Io 25),
the trajectory is predictable only in a statistical sense and only reliably
for one or two orbits. It's a highly nonlinear, chaotic system
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:29PM PDT
(-0700 GMT)
EVERYONE: Who's the youngest we've got on the chat right now?
I am 17
Looks like Silvio from Italy is the youngest. He says he is 8.
Aso De Pacaro - I'm sorry for my english. I (tried) to say that the
asteroid question was generated when I was 8 years old. Now I'm pretty
older... :-)
Of course, my age is PI, but I won't tell you what calendar I go by.
steve: im 13
RAC: . . . . Thu, Apr 10, 4:31PM PDT (-0700 GMT)
I must say , I am impressed!
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:31PM PDT
(-0700 GMT)
Jo: I have a G1 fact sheet that gives the G/A delta-v and the effects on
the Jupiter orbit of the G1 G/A. If there's something specific, I can
answer that now.
Marc: . . . . Thu, Apr 10, 4:32PM PDT (-0700 GMT)
Hi. I just want to say I'm enjoying reading these comments and questions.
There are so many people commenting so quickly that I can't keep up.
When I finish reading, I reload and there's another batch of comments.
aLiEn: . . . . Thu, Apr 10, 4:32PM PDT (-0700 GMT)
by the way, i have to ask questions to get extra credit, any1 want to
answer my questions?
aLiEn, ask away.
Mr Jo: um..well.. what exaclty are you trying to do?
Steve Collins Galileo Attitude Control: . . . . Thu, Apr 10, 4:32PM PDT
(-0700 GMT)
I want to hear a few questions from the 18 or younger people...
espaŅol: . . . . Thu, Apr 10, 4:33PM PDT (-0700 GMT)
Edward: podrias darme tu direccion de e-mail por si se me ocurre algo
respecto a la sonda.
pensando...
espanol: Solo mandale el mensaje a 'askgalileo@jpl.nasa.gov' y los
encargados me la haran llegar.
RAC: . . . . Thu, Apr 10, 4:34PM PDT (-0700 GMT)
Was the decision to concentrate the GEM on Europa made after the ice
"rafts" were discovered or before?
RAC, the decision to concentrate GEM on Europa was made long
ago: it's long been considered the most interesting moon
in the system. Io is also of great interest, but having
to deal with the radiation field is a major technical
problem.
Hi RAC, GEM was decided upon last year, long before the latest images
became available. There were some interesting alternatives discussed.
Lou D'Amario, Galileo Navigation Team: . . . . Thu, Apr 10, 4:36PM PDT
(-0700 GMT)
Jo: Your list of ultimate fates for Galileo was not ordered correctly.
Impacting a satellite is the most likely eventual outcome, followed (in
decreasing likelihood) by impacting Jupiter and escape from the Jupiter
system.
Thanks, Lou.
Spiff: . . . . Thu, Apr 10, 4:36PM PDT (-0700 GMT)
Jim Taylor : What other (modelled) events effect your Doppler=shift
besides the calculated velocity and thruster flushes ?
Spiff, you asked what (besides modeled and unmodeled velocity changes)
affects the doppler. That's the only thing, if you include acceleration
and rate of change of acceleration in your definition of velocity. The
thruster flushes, for example, impart a small change in the spacecraft's
velocity. Perhaps I wasn't clear before about the "unmodeled" doppler.
The thrust level, for example, is known very well. It's just that the
modeled time of a thruster firing (transmitted to the stations as a
prediction) did not agree within less than one second of the actual
thrusting time. The new receivers require that degree of accuracy because
of the very narrow carrier tracking loop and the impulsive nature velocity
change caused by thrusting. The whole field of radio science and quite a
bit of navigation depends on observing changes in the radio signals, such
as doppler. "One man's noise is another man's data" is a famous radio
science saying. As a radio link operator, I'd like a! In absolutely
steady signal. That would be very boring to a radio scientist. 8-)
Jim Lukash: . . . . Thu, Apr 10, 4:37PM PDT (-0700 GMT)
Thank You again, Jo (Jo Pitesky, Galileo Outreach:) for the response. I'm
afraid I must go, it is one of those evenings when I wonder why I moved
from Huntington Beach CA to Denver CO.(It is snowing in Denver) I want to
thank all the team members who participated for their time. Keep up the
good work, Ladies and Gentlemen. Thank You and Farewell.
RAC: . . . . Thu, Apr 10, 4:37PM PDT (-0700 GMT)
If the spacecraft will be unuseable after 12/99 then how about a controlled
descent into jupiters atmosphere to see what additional data you can get.
(Better than just turning it off..the end of Pioneer 10 seemed so pitiful!)
RAC: That would be some controlled descent: the probe needed
an aeroshell to protect against the heat of entry, and a
parachute to slow down. The orbiter just isn't built to
handle conditions like that.
RAC: I like your idea!
RAC: If the spacecraft is unusable in a science gathering sense at the end
of GEM, then it is probably also uncontrollable, because we would need
functioneing onboard computers to perform propulsive maneuvers.
RAC, what they turned off on Pioneer 10 was the last of the science
instruments, and allocating ground stations to track the spacecraft. I
understand that the spacecraft's radio transmitter is still operative, at
least for a while. A press release from NASA Ames Center (operator of
Pioneer) said the spacecraft would still be "tracked" in the process of
training mission operators for their lunar mission (Clementine?) I agree
with you that it's up to us to figure out and sell science-valuable
end-of-mission activities.
Marc: . . . . Thu, Apr 10, 4:38PM PDT (-0700 GMT)
How important is Europa in the grand scheme of things?
Wouldn't we be better off focusing our resources (in future missions) on
looking for life on Mars and doing the kind of research that will prepare
us for colonizing our own corner the solar system?
Hi Marc, Even if Europa were lifeless it is important in understanding
our own world - after all, it is a rocky planet with a layer of water
and ice on its surface - sound familiar?
Marc - One of the main differences between Mars and Europa is that
mars used to have liquid water 3.5 billion years ago, most of it is
now either gone or frozen. The neat thing about Europa is that the
water is most probably liquid beneath it's ice shell, providing
an environment for life to exist today.
Marc: One of the things that solar system research gives us (besides
fantastic pictures) is a view of how changing conditions on Earth
will influence the Earth's evolution. Europa is the only place
in the solar system where we think there may yet be liquid water;
on Mars, it's frozen. We're looking for information on how
to preserve our own home, not just on how to colonize.
Finally, quoting from yesterday's press
conference, to the first order, the hunt for life on Mars will be
a fossil hunt. To first order, the hunt for life on
Europa will be for actual life.
Nancy Vandermey, Seq-Sys: . . . . Thu, Apr 10, 4:38PM PDT (-0700 GMT)
The power does not degrade completely by the end of GEM, however if Dec
1999 wasn't the en