Background for Jupiter Atmospheric Observations

Jupiter's atmosphere displays a rich variety of activity that is not well understood. Cloud belts are symmetrically aligned parallel to the equator. The cloud belts are associated with atmospheric jet streams that alternate between east and west directions, at different latitudes. Between the jet streams there are numerous circulating ovals of cloud, some of which have very long lifetimes. The largest of these, the Great Red Spot, has been in existence for over 300 years, since the first recorded observations of the planet. In addition to the long lived jets and spots there is a large amount of turbulent activity. It is not known how the jets and ovals can persist without turbulence tearing them apart. One suggestion is that the turbulence may even help maintain the organization of the flow, but there is no detailed understanding of how this would happen.

The new instruments on the Galileo Orbiter provide the first time capability to probe many different depths simultaneously, and reveal a three dimensional picture of the cloud structures and the winds. This information brings us a step closer to understanding the behavior of Jupiter's atmosphere.

General Plan

Jupiter's atmosphere will be observed with high resolution images that focus on local regions. Each selected region will have some special feature or some special atmospheric behavior. For example, one feature will be the Great Red Spot, another will be a particularly strong jet stream, and another will be a plume of cloud that might be caused by a convective storm.

Each feature selected for detailed observation will be observed by infrared and ultraviolet instruments as well as by the Galileo camera. In this way a more complete description of the atmospheric cloud structure, composition, and temperature will be obtained.

A typical region to be examined will be approximately as wide as one of Jupiter's cloud belts, about 16,000 km across. (The diameter of the Earth is about 12,000 km.) Within this region, the Galileo camera will detect features as small as 15 km, which should resolve even the smallest clouds that exist.

Jupiter rotates approximately once every ten hours. Time lapsed images will be taken of each region, first with a difference in time of about two hours and also with a difference in time of about ten hours or one full rotation later. These time delayed images allow measurement of cloud motion and hence wind speed and direction. (See our GRS blink frame "movie".)

Each set of images will be taken through filters that select certain colors, or wavelengths of light. Four different wavelengths will typically be used. Since light of different wavelengths penetrates to different depths in Jupiter's atmosphere, this filter strategy reveals different cloud structures at different depths and permits wind measurments at different depths. The different filters also provide information on coloring agents, or chromophores, in Jupiter's clouds. What makes the Great Red Spot appear red?

As the Galileo mission progresses, the SSI camera will observe a series of regions on Jupiter. Each region is selected to focus on a particular target, and the targets are selected so that all latitudes on the planet are examined by the end of the mission.

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Galileo Solid State Imaging Team Leader: Dr. Michael J. S. Belton

The SSI Education and Public Outreach webpages were originally created and managed by Matthew Fishburn and Elizabeth Alvarez with significant assistance from Kelly Bender, Ross Beyer, Detrick Branston, Stephanie Lyons, Eileen Ryan, and Nalin Samarasinha.

Last updated: September 17, 1999, by Matthew Fishburn

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