Dr. Cristina Dalle Ore

December 20, 2006

“Planetary Surfaces and Atmospheres: a Reprise”

NCC 2–1339

The solid bodies of the Solar System include the natural satellites of the outer planets, the planet Pluto, the asteroids, the Centaur objects, the Kuiper Belt objects, the comets and Saturn's rings.The study of their surfaces can shed light on their history: how they formed and where, how they developed and interacted with other bodies in their vicinity. The largest of the Solar System bodies are known to have atmospheres, but more bodies might have a tenuous and transitory atmosphere. Furthermore, in the outer Solar System where very low temperatures keep volatile materials frozen, small changes in temperature can trigger exchanges of molecular material between the surface and the atmosphere. The changes in temperatures could be caused by variations in solar activity, tidal and or magnetic interactions as well as other unidentified factors. A well documented example of such interaction between surface and atmosphere is Triton whose surface shows signs of change with a frequency of only a few months. Its albedo changes by a factor of about two in the UV region of the spectrum for causes yet to be known, but resembles the effect of ‘snowstorms’.

Titan, one of Saturn’s satellites has a thick, opaque atmosphere due to photochemical smog. Windows in the atmospheric spectrum may allow us to have a chance to observe the lower atmosphere as well as the surface and possibly infer their composition. Furthermore, the materials that make up its atmosphere have been reproduced and processed in the laboratory to yield an organic mixture that could make up some of the surface composition of other outer Solar System bodies, tying their histories together. Europa, the second largest satellite of Jupiter, has been gathering a lot of attention because of what looks like an ocean of liquid water underneath a possibly thin icy crust. Because of the tidal interaction between Europa, Jupiter and the other neighboring satellites, there is enough energy stored in its water to allow for possible forms of life, current or fossil.

Our goal is twofold: to continue gathering, processing and interpreting telescopic observations (both from ground and space), to obtain more information on the composition of the Solar System small bodies, and to infer the relevance of our findings from the astrobiological standpoint.