Biology
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmmr22a..01n&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #MR22A-01
Biology
[3902] Mineral Physics / Creep And Deformation, [5220] Planetary Sciences: Astrobiology / Hydrothermal Systems And Weathering On Other Planets, [5422] Planetary Sciences: Solid Surface Planets / Ices, [5480] Planetary Sciences: Solid Surface Planets / Volcanism
Scientific paper
A possible definition of a habitable environment is one that has liquid water, a range of suitable prebiotic compounds (however defined), and a source of energy. An ocean-bearing icy satellite can provide the first two quite easily, as well as giving protection from radiation. The third requirement is most readily provided by redox reactants, which may arise from hydrothermal activity, solar ultraviolet radiation, or impacts [1-4]. Reactants produced at the surface must thus be transported through the ice shell to the underlying liquid, while hydrothermal activity requires contact between hot silicates and the ocean. Large satellites, such as Ganymede, possessing denser ice phases beneath the ocean are thus less plausibly habitable. As far as ice properties are concerned, there are two key issues. The first is the ability of ice to insulate an underlying ocean, thus controlling its lifetime. This depends on whether the ice is convecting (which in turn depends on grain size, shell thickness, basal temperature etc. [5]), the extent to which the ice shell is tidally heated, and the thermal conductivity of the ice (clathrates are good insulators [6]). For instance, Enceladus is sufficiently small that its putative ocean is expected to freeze on timescales of tens of Myr [7], reducing its potential habitability. On the other hand, ice shells above ammonia-rich oceans are likely to have lower basal temperatures and thus freeze more slowly [8]. The second issue is the extent to which the ice allows communication between the surface and subsurface. Getting material from the surface to the ocean, or vice versa, is difficult because convecting ice typically has a thick, stagnant lid [9]. But there may be situations in which this stagnant lid does not occur, for instance if the ice has a low yield strength. Brittle failure might also allow communication between the ocean and the surface [9] (as appears to happen at Enceladus [10]), while melt production due to shear heating [11] might enhance downwards transportation rates. A less obvious issue is the extent to which the silicate portion of the satellites can be heated. This is because 1) hot silicates prolong the life of an overlying ocean and 2) hydrothermal circulation is a source of reactants. Europa [12] and Enceladus [13] may both possess hot, partially-molten silicate interiors. However, at least for Enceladus the temperatures inferred by [13] cannot be explained by conventional tidal heating [7]. One possibility is that the conventional Maxwell viscoelastic rheological model does not adequately describe dissipation in real geological materials [14], and that more complicated descriptions are required. [1] Gaidos EJ, Science 284, 1631-33, 1999. [2] Hand KP et al., Astrobiology 7, 1006-22, 2007. [3] Zolotov MY Shock EL, JGR 109, E06003, 2004. [4] Schulze-Makuch D, Irwin LN Astrobiology 2, 105-21, 2002. [5] Barr AC, McKinnon WB, JGR 112, E02012, 2007. [6] Ross RG, Kargel JS, in Solar System Ices, 33-62, 1998. [7] Roberts JH, Nimmo F, Icarus 194, 675-89, 2008. [8] Deschamps F, Sotin C, JGR 106, 5107-21, 2001. [9] Barr AC et al., LPSC 33, 1545, 2002. [10] Postberg F et al., Nature 459, 1098-1101, 2009. [11] Nimmo F, Gaidos E, JGR 107, 5021, 2002. [12] Greenberg R et al., Rev. Geophys. 40, 1004, 2002. [13] Matson DL et al., Icarus 187, 569-73, 2007. [14] McCarthy C et al., LPSC 39, 2512, 2008.
No associations
LandOfFree
How do the physical properties of ice influence the habitability of outer solar system satellites? (Invited) does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with How do the physical properties of ice influence the habitability of outer solar system satellites? (Invited), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and How do the physical properties of ice influence the habitability of outer solar system satellites? (Invited) will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1777163