Mathematics – Probability
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmmr13a1692s&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #MR13A-1692
Mathematics
Probability
5215 Origin Of Life, 6040 Origin And Evolution, 6205 Asteroids, 6224 Kuiper Belt Objects
Scientific paper
Much attention has been focused on the few large satellites of Jupiter and Saturn that have evidence of interior layers of liquid water, and the possibility that they may be suitable habitats for life. For life to evolve in these regions, they would have to, at a minimum, produce the necessary chemical constituents to provide energy for building organic matter, be protected from temperature extremes and radiation, and last long enough for evolution to progress. The type of organisms that could form in such habitats could be similar to those that evolved in the pre-photosynthetic, anoxic early Earth. The probability of extra-terrestrial life evolving in our solar system would increase greatly if such suitable habitats had been more common. We examine the possibilities for suitable habitats in the more numerous set of moderate-sized (< 1000 km in diameter) ice-rich planetesimals that may populate the Asteroid Belt and Kuiper Belt. We modeled the thermal evolution of 200-1000 km planetesimals, assuming cold accretion of undifferentiated bodies comprised of a mixture of chondritic rock and water ice. The heat sources for these planetesimals are short- and long-lived radioactive isotopes, and the latent heat from hydration reactions. We vary the planetesimals initial size, surface temperature, ice/rock ratio and the 26Al content (which is very sensitive to the timing of accretion). Each modeled planetesimal undergoes a pulse of radioactive heating, followed by slow cooling. Some water from the melting ice phase migrates upward to form an "internal ocean" layer beneath a still frozen crust, while some water reacts with the remaining rock to form a hydrated silicate (serpentinized) core. In warmer planetesimals, these hydrated silicates can break-down, and a second phase of water production and migration occurs. If the frozen rock/ice crust becomes too thin, we assume that crustal overturn will result in loss of any underlying liquid. Many models produce liquid water layers lasting hundreds of millions of years. These water layers overlay a large core of serpentinzing silicate, which would be producing hydrogen, methane, sulfate and possibly complex organics to the water layer. We will explore the possible biogeochemical cycling that could develop in these systems.
Farrell L. L.
McGary Robeson S.
Sparks David W.
Tice Michael M.
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