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D.W. Williams, B.L. Sands (Penn State Erie, The Behrend College)
Today nearly 20 Jupiter-sized planets are known to orbit within or near the habitable zones of their parent stars [see Williams D.W. and Pollard, D. 2001. submitted Inter. J. Astrobiology]. Some of these planets might support life on their moons if their moons are able to form and hold onto sizeable atmospheres. Moons larger than ~0.2 Mearth should have little trouble holding their atmospheres for billions of years [Williams D.W., Kasting, J.F., & Wade R.A. 1997. Nature 385,234]. But forming moons of this size through pair-wise accretion of small bodies in low-mass circum-planetary nebulas may be difficult; Ganymede (0.03 Mearth) was the largest moon to form out of a circum-planetary nebula in the Solar System. A more plausible scenario is for giant moons to be captured through collision of an earth-sized planetary body with a gaseous proto-planetary disk around a giant planet, as is thought to have occurred to form Triton around Neptune [McKinnon, W.B., & Leith, A.C. 1995. Icarus 118,392]. Such collisions can remove enormous amounts of energy from the impacting body and often result in a bound satellite on a near-circular orbit. Here we demonstrate that for a reasonable set of nebula parameters such captured moons can avoid spiraling into their planets on timescales comparable to or greater than the lifetime of a circum-planetary nebula.
The author(s) of this abstract have provided an email address for comments about the abstract: dmw145@psu.edu