Table of Contents

• Overview of Io Facts
• Latest Io Science Findings
• Io Images
• Missions Exploring Io
• Educational Activities and Resources
• The Mythology of Jupiter and Its Satellites
• The Discovery of the Galilean Satellites
• Frequently asked Questions (FAQs) about Io
• Resources
• Links to Related Sites

Overview of Io Facts

Io Quick-Look Statistics

 
Discovery:                             Jan 7, 1610 by Galileo Galilei
Diameter (km):                              3,630
Mass (kg):                                  8.94x10?22 
Mass (Earth = 1)                            0.014960 
Surface Gravity (Earth = 1):                0.183 
Mean Distance from Jupiter (km):            421,600 
Mean Distance From Jupiter (Rj):            5.905 
Mean Distance from Sun (AU):                5.20 
Orbital period (days):                      1.769138 
Rotational period  (days):                  1.769138 
Density (gm/cm?3)                           3.57 
Orbit Eccentricity:                         0.0041 
Orbit Inclination (degrees):                0.040 
Orbit Speed (km/sec):                       17.34 
Escape velocity (km/sec):                   2.56 
Visual Albedo:                              0.61 
Typical Subsolar Temperature (K)            ~135 
Typical Hotspot Temperature (K)             ~300
Surface Composition:                        Sulphur

A Summary of Facts about Io

Latest Io Science Findings

General/Overview:

• Possible Internal Structures of the Galilean Satellites (November 18, 1997).
• Galileo Finds Iron Core In Io (May 3, 1996)

Volcanic Changes:

• Galileo Spacecraft Sees Volcanic Fireworks On Jupiter's Moon Io (July 2, 1998)
• Galileo Finds Arizona-Sized Volcanic Deposit on Io (November 5, 1997)
• Galileo Finds High-Altitude Ionosphere at Io (October 23, 1996)
• Galileo Finds Big Changes in Io (July 18, 1996)

Atmosphere:

• New Jupiter Findings: Oxygen at Callisto's Surface, Sulfur Dioxide Sources At Io (December 10, 1997).
• Galileo Finds High-Altitude Ionosphere at Io (October 23, 1996)

Frequently Asked Questions about Io

Io Images

Galileo Images

• Global Clickable Maps (Organized by location)
• Image Tables Organized by Features and Orbit
  Io Encounter Animations from Galileo Images

Look here for information on how to setup your browser for animations.

• Io in Rotation/Volcanoes Erupting
  • (AVI - 3.8 MB)
  • (AVI - 2.6 MB)
• Io Plume Monitoring Animation (September 2-6, 1996).

• Io Pillan Patera Flyby
  • (MOV - 5.5 MB)
• Io Plume Monitoring Animation (September 2-6, 1996).

Images from Other Missions

• Voyager 1 & 2 Images
• Hubble Space Telescope Images
  • Hubble Satellite "Family Portrait"
  • Hubble Image of Jupiter and Io (July 24, 1996)
  • Hubble Discovers Bright New Spot on Io (October 10, 1995)
• Pioneer 11 Images

Animations from Non-Galileo Data
Look here for information on how to setup your browser for animations.

• Io Rotation Movie
  • (AVI - 363K)
  • (MPG - 158K)
• Model of the Io Plasma Torus (MPG - 552K)

Missions Exploring Io

• Galileo Europa Mission (GEM): Dec. 1997 - Dec. 1999
• Galileo Nominal Mission: Dec. 1995 - Dec. 1997

Educational Activities and Resources

• Activities:
  • Moons in Resonance
  • Flexing Muscles and Moons
  • What's So HOT About Io?
  • Planets and Satellites (Overview of our solar system and the Jovian system)
  • Planetary Surfaces
  • More activities
• Galileo K-12 Educator's Resources
• Bulletin Boards and Stickers
• The Jovian system as viewed from Earth (Java Applet)

The Mythology of Jupiter and Its Satellites
The planets and moons in our solar system are all named for characters in Greek and Roman mythology. Here are some stories and artwork about the namesakes of Jupiter and the Galilean satellites.

USGS Io Nomenclature page

The Discovery of the Galilean Satellites
Find out how Galileo Galilei discovered the moons around Jupiter.

Frequently asked Questions (FAQs)

• General Galileo FAQ's
• Online From Jupiter FAQ (April 6, 1997)

Resources

• Ask Galileo A Question
• Definitions and Acronyms

• Subscribe to the Galileo Mailing List!

Links to Related Sites

• Galileo homepage at the Jet Propulsion Laboratory
• Galileo Io Mission webpage at the Jet Propulsion Laboratory
• Galileo homepage at the DLR in Germany
• Galileo Probe
  • Probe Team at Ames Research Center
  • NMS - Neutral Mass Spectrometer
• Galileo Orbiter
  • DDS - Dust Detector
  • EPD - Energetic Particles Detector Team
  • HIC - Heavy Ion Counter
  • MAG - Galileo Magnetometer Team
  • NIMS - Near Infrared Mapping Spectrometer
  • PLS - Galileo Plasma Particle Investigation
  • PWS - University of Iowa Space Plasma Wave Group
  • SSI - Solid State Imaging Team
  • UVS/EUV - Ultraviolet Spectrometer/Extreme Ultraviolet Spectrometer Experiment
• Space Science Background Information
  • NASA's Spacelink
  • The Nine Planets
  • Views of the Solar System
  • NASA's Planetary Photojournal