DPS Meeting, Madison, October 1998
Session 35. Invited Talk: Clark Chapman, Europa Perspectives Halfway through the GEM Mission
Invited Plenary Session, Thursday, October 15, 1998, 8:00-8:45am, Madison Ballroom A and B

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[35.01] Europa: Perspectives Halfway through the GEM Mission

C. R. Chapman (SwRI), The Galileo Imaging Team

We are now nearly a year past the end of the prime Galileo mission (orbital tour) and are approaching the halfway point of the Galileo Europa Mission (GEM). Plans are being formulated for follow-on missions. I will review Galileo results concerning Europa, emphasizing evidence from imaging concerning the near-surface interior of Europa (i.e. the putative sub-ice ocean). It is the photogeologist's difficult task to infer the nature of the subsurface third dimension from two-dimensional images of a planet's surface. The remarkably intricate patterns of ridges, cracks, pits, domes, and chaotic zones on Europa strongly constrain surface processes but are less diagnostic of the subsurface. The issue of time (ages and rates) is always a conundrum in geology and it is especially significant for Europa. Does Europa present us with a frozen tableau of the ancient past or a snapshot of a currently active world with surface units only hundreds of thousands to millions of years old? Is its geological style cyclical or even episodic? Does the evidence for "liquidity" below Europa's brittle crust imply actual water or only low-viscosity ice? If water, how close to the surface is it (a) on average and (b) at the shallowest locations? Galileo's evidence suggests, but has not yet proved, that Europa is the most likely currently habitable place in the solar system beyond the Earth.

The author(s) of this abstract have provided an email address for comments about the abstract: cchapman@boulder.swri.edu

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