This Image Guide undergoes frequent updates since the Galileo project adapts to new discoveries and changing constraints as the mission progresses.

This guide contains both the Satellite Science Goals and the Atmospheric Science Goals, please page down for the Atmospheric Science Goals.

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Satellite Science Goals

1. Characterize the morphology, geology, and physical state of the satellite surfaces
2. Investigate the satellites surface mineralogy and determine the distribution of the compositional units
3. Determine the satellites gravitational fields, magnetic fields and dynamic properties
4. Study satellite atmospheres and ionospheres, extended gas clouds arising from the satellites, and interactions with the magnetosphere

1. Geological evolution of Io and Europa (samples < 1 km)
2. Geological evolution of Ganymede and Callisto (samples < 100 m)
3. Nature of current Io volcanism/variability
   (target plumes, surface flows, frosts, dark side search for silicate volcanism)
4. Global context for #1.
   (Europa moderate resolution regional coverage - some with color)
5. Global context for #2.
   (regional moderate resolution < 2km - some with color)
6. Global context for #2 (Callisto color samples)
7. Surface composition of all satellites (photometric properties of all)
8. Origin and mass balance of ring material
9. Additional regional Callisto coverage (< 2km)
10. Voyager complimentary coverage in color (to extent possible)

Ganymede

• Science Objectives
  Ganymede was well imaged by Voyager so most resources are devoted to high resolution observations.
  1. Characterize any volcanism
  2. Determine the nature and timing of any tectonic activity
  3. Determine the history of formation and degradation of impact craters
  4. Determine the nature of the surface materials
  
  

• Image Sequence

  Orbit G1

  Geodetic Control

  Latitude and longitude of center of frame:	-6, 153
  Date of Observation:	June 26, 1996
  # of Frames in mosaic:	0.8

  Description of the Area:
  

  This frame, together with others, will be used to compute the geodetic control network of Ganymede. The network will define the latitude and longitude grid for cartographic purposes and also measure the radius of Ganymede.

  Questions we hope to answer:

  • What is the exact radius of Ganymede?
  • What are the definitive latitudes and longitudes for features on the surface?

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  Color Global

  Latitude and longitude of center of frame:	-6, 153
  Date of Observation:	June 26, 1996
  # of Frames in mosaic:	5

  Description of the Area:
  

  This five color sequence covers representative examples of nearly all types of albedo features on Ganymede: light and dark terrain of differing age and albedo, part of the reddened textures.

Uruk Sulcus

Latitude and longitude of center of frame:	11.34, 168.1
Date of Observation:	June 27, 1996
# of Frames in mosaic:	4

Description of the Area:

Western Uruk Sulcus contains a confined band of light material and grooves having a moderately complex stratigraphy, bounded by Galileo Regio to the north and Marius Regio to the south. The margin of Galileo Regio is partly broken up into small deformed blocks, on which light mantling deposits have been superimposed. The lines along which breakup occurred, which have been occupied by groove lanes having a regionally dominant NE-SW trend, appear to be defined by furrows in the dark terrain. This observation will sample the bright grooved terrain of Uruk Sulcus at high resolution.

Questions we hope to answer:

• What is the light terrain and where did it come from?
  • In Uruk Sulcus, the light material seems only to be a very thin coating on older rough dark terrain. This could be evidence of explosive eruptions predicted to accompany extrusion of ice-volcanic melts. Higher resolution images of this area will help to answer this.
  • A better understanding of the complex stratigraphy of the light terrain at high resolution, will give us insight into the history of resurfacing and deformational processes. This will help us to understand the basic geologic processes that formed the light terrain.
    
• What is the origin of grooves in Ganymede's bright terrain?
• How does groove morphology change in different terrain types?
  
• Why do the groove lanes have a common orientation?
  • On a global scale?
  • On a regional scale?
• What is the detailed morphology of the deformed dark blocks along the margin of Galileo Regio?
  
• What are the crater morphologies like in this region?
  
  • How do they relate to those in other regions, and what do they tell us about craters on Ganymede?
• What are the albedo patterns in the light terrain and what can they tell us about the geology and physical characteristics of those regions?
  

Galileo Regio

Latitude and longitude of center of frame:	18.5, 147.9
Date of Observation:	June 27, 1996
# of Frames in mosaic:	5

Description of the Area:

This area contains furrows of several orientations. In some cases the furrows cross-cut one another. There are also intervening patches of dark smooth material, which might be volcanic in origin. In the center where all the frames overlap, there is a feature that could either be a small palimpsest (an ancient impact scar) or a crater which is partly buried by material that emanated from a furrow or other source.

Questions we hope to answer:

• What is the morphology of the furrows and what are the relative ages of features in Galileo Regio?
• What is the geological history of the dark terrain in this location?
  • What are the albedo patterns in the dark terrain and what can they tell us about the geology and physical details of those regions?
• What are the crater morphologies like in this region?
  • How are Ganymede craters similar to or different from craters on other planetary bodies?

Memphis Facula

Latitude and longitude of first and last frame:	16.15, 135.6 to 14.32, 132.2
Date of Observation:	June 27, 1996
# of Frames in mosaic:	4

Description of the Area:

Memphis Facula is the archetypal palimpsest, an ancient impact scar which is distinctly bright against the dark cratered terrain of Galileo Regio. It occurs on a background of furrowed dark terrain, with small patches of dark smooth materials appearing to fill the low spots between furrows. The images across the palimpsest will provide information as to the origin and evolution of this and similar low-relief impact scars.

Questions we hope to answer:

• What is the nature of palimpsests on Ganymede?
  
  • Why are palimpsests brighter than the surrounding terrain?
    
  • Palimpsests have a range of topographies; they can be flat to basin-like, and some have central domes. Are there any indications of the factors that control final palimpsest topography?
    
  • What role has the resurfacing of Ganymede played in modifying the palimpsests?
• What is the range of crater morphologies in the palimpsest region and how does it relate to craters in other regions?
  
• How was the dark material emplaced on the surface?

Unnamed Sulcus

Latitude and longitude of center of frame:	30, 90
Date of Observation:	June 27, 1996
# of Frames in mosaic:	4

Description of the Area:

This sequence will aquire very high resolution images of a portion of bright terrain between Galileo and Perrine Regios. We expect to see grooved terrain, similar to what is seen in the Uruk Sulcus images, and will compare the orientations and morphologies to those seen in the Uruk Sulcus images. This area has not been imaged before at even a moderate resolution (moderate resolution images will be taken on orbit C9). This is an exploratory observation which will provide a richness of information about the nature of Ganymede's surface at the very highest resolution attainable with Galileo. Never before has the surface of an icy satellite been imaged at such high resolution.

Questions we hope to answer:

• What is the character of Ganymede's surface at such small scales?
• What is the detailed nature of the grooved terrain?
  
  • Are primary structures such as fault scarps preserved in these terrains?
    
  • To what extent has the grooved terrain been modified (by such processes as viscous relaxation, sublimation, or mass wasting)?
• Are very small craters preserved on the surface?
  • If so, this will be useful in determining the age of the surface.
    
  • It might also provide information about the depth and nature of the regolith on the surface of Ganymede.

Europa

• Science Objectives
  Europa was poorly imaged by Voyager so the plan includes a mix of high resolution and low resolution observations to provide context.
  1. Determine the nature, origin, and age of the tectonic features
  2. Determine the nature, rates and sequence of resurfacing events
  3. Assess the cratering history
  4. Map spectral and photometric properties

• Image Sequence

Global Frames

North Pole

Description of the Area:

This mosaic covers a large section of mostly unknown terrain on Europa. Image resolution exceeds the highest obtained over limited areas by Voyager (e.g., right side of view). The right edge of the mosaic includes the terminator, where the morphology of Europa's low-relief surface will be seen to advantage. The northern quarter of the mosaic includes the north pole. This view is the best opportunity during the mission to view the regions around either pole. (We do not have an opportunity to view the south pole.) The three-color footprint uses a filter unique to Galileo SSI, and covers polar latitudes down to 40N.

Questions we hope to answer:

• What is the occurrence and distribution of major surface features across the unexplored terrain?
• Are there any features in this area that should be explored in further detail on future orbits?
• How does the north polar area differ from more equatorial terrain, in feature inventory and color?
• What is the relief and morphology of surface features previously seen at high sun by Voyager?
• Have there been any surface changes in the area seen by Voyager (right side of view) since 1979?
• How does radiation noise affect the quality and compression potential of SSI images of Europa?

1. Determine chemical composition
2. Determine structure to a pressure depth of at least 10 bars
3. Determine nature of cloud particles and location and structure of cloud lay ers
4. Determine radiative energy balance
5. Investigate circulation and dynamics
6. Investigate upper atmosphere and ionosphere

1. Why are there bands and jets on Jupiter?
2. How is heat transported from the interior?
3. Why are jets stable?
4. Why are hotspots and ovals stable?
5. Are clouds passive tracers or active dynamically in causing jets and bands?
6. Why do the clouds have colors?
7. How are clouds formed?
8. What trace chemicals are present?
   How are they created and transported?
9. What hazes exist in the stratosphere?
   How do they affect deeper clouds?

Imaging Sequence

Great Red Spot

Latitude and longitude of center of frame:	-22.3, 318
Date of Observation:	June 26, 1996
Total # of Frames to be taken:	70

Description of the Area:

The Great Red Spot has been observed on Jupiter since the 17th century, when it was discovered by the first telescopic observations of the planet. It is about three Earth diameters in the East-West direction and two Earth diameters in the North-South direction. It contains a circulating anti-cyclonic flow that takes about six days to complete one rotation. The spot greatly perturbs the neighboring turbulent cloud structures.

The Great Red Spot observations will be a 2x3 rectangular array of images, two frames wide in the North-South direction and three frames wide in the East-West direction. Images will be shuttered at four different times, and in four different colors. There will be 70 frames altogether.

Questions we hope to answer:

• Why has the Great Red Spot remained in existance for over 300 years given the large amount of turbulent activity within the Jovian atmosphere?
• What is the cloud structure, composition, and temperature within the Great Red Spot?
• How deep into Jupiter's atmosphere does the red spot extend?
• What are the speeds and directions of the winds within the Great Red Spot?
• What causes the reddish color within the Great Red Spot?

The National Optical Astronomy Observatories are operated by AURA Inc. under contract to the National Science Foundation.

Last updated: June 22, 1996, by Ross Beyer