Phobos, the inner, asteroid-like satellite of Mars, is only 20 km diameter yet exhibits a perplexing geology. Orbiting well inside the corotation radius, and also inside the Roche limit, it will spiral into Mars in a few ten million years, and experiences increasing tidal deformation. Several features stand out: the crater Stickney, almost 10 km diameter, and complex networks of striations and pitted grooves. This talk will emphasize our recent work, that shows that the patterned striations are formed by the distortion of a weak elastic shell overlying an even weaker deformable interior (Hurford et al., in review) and that the pitted grooves are sesquinary catenae formed by the eventual re-impact of ejected material (Nayak and Asphaug, in review). Long considered a possible outpost for human exploration, Phobos has a continually active geology that would be hazardous. Deimos, farther from Mars and not experiencing increasing tides, is a safer venue.
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Institute for Planets and Exoplanets
