Is there life on … Titan?

Abstract

Lucy H Norman and A Dominic Fortes consider the possibilities for life on and in Saturn's complex icy moon, and the nature of organisms that might live there.

Modeling ammonia–ammonium aqueous chemistries in the Solar System’s icy bodies

“…Assuming Titan behaves similarly to a Europa example (Marion et al, 2005;, with a surface temperature on Titan of 94 K (Coustenis, 2007), this could place a subsurface ocean temperature at 250 K with 240 bars of pressure, approximately 20 km beneath the surface. So assumptions that oceans on Titan might exist within a few tens of kilometers of the surface (Tobie et al, 2005;Beghin et al, 2010;Norman and Fortes, 2011) is possible and with respect to temperature could support life as we know it on Earth. The activity of water (a w ) (Fig.…”

“…There have been numerous studies in recent years dealing with the chemistries of subsurface fluids on Titan, especially with respect to (NH 4 ) 2 SO 4 , NH 3 , and CH 4 Á6H 2 O (Osegovic and Max, 2005;Atreya et al, 2006;Fortes et al, 2007;Spencer and Grinspoon, 2007;Grindrod et al, 2008;Sohl et al, 2010;Norman and Fortes, 2011;Fortes, 2012). Theory suggests that there may be subsurface water oceans on Titan (Fortes, 2000;Baker et al, 2005;Tobie et al, 2005;Fortes et al, 2007;Sotin and Tobie, 2008;Sohl et al, 2010) that are today as close to 50 km of the surface and for much of the past may have been within 10-20 km (Tobie et al, 2005).…”

“…11) 2008). Such shallow oceans may have been present on Titan in the recent past, or even at present (Tobie et al, 2005;Norman and Fortes, 2011). This simulation caused (NH 4 ) 2 SO 4 to start precipitating at 273 K, ice to start precipitating at 241 K, CH 4 Á6H 2 O to start precipitating at 209 K, and NH 4 Cl to start precipitating at 203 K. The largest difference between these two simulations was in the formation of CH 4 Á6H 2 O, which started respectively at 226 K at 10 bars of pressure (Fig.…”

Exomoon Habitability Constrained by Illumination and Tidal Heating

“…It is the only moon known to have a substantial atmosphere. Tides exerted by the Sun on Titan's host planet, Saturn, are relatively weak, which is why the planet could maintain its spin-orbit misalignment, or obliquity, w p of 26.7° (Norman, 2011). Titan orbits Saturn in the planet's equatorial plane with no significant tilt of its rotation axis with respect to its circumplanetary orbit.…”

Modeling nitrogen and methane with ethane and propane gas hydrates at low temperatures (173–290K) with applications to Titan

“…There have been numerous studies in recent years dealing with the chemistries of subsurface fluids on Titan, especially with respect to (NH 4 ) 2 SO 4 , NH 3 , and CH 4 •6H 2 O (Osegovic and Max, 2005;Atreya et al, 2006;Fortes et al, 2007;Spencer and Grinspoon, 2007;Grindrod et al, 2008;Tobie et al, 2009;Fortes and Choukroun, 2010;Sohl et al, 2010;Norman and Fortes, 2011;Fortes, 2012;Marion et al, 2012Marion et al, , 2014Vance et al, 2012;Glein, 2015). Cassini has discovered a subsurface water ocean on Titan (less et al, 2012), which was previously predicted by many interior models (Fortes, 2000;Baker et al, 2005;Tobie et al, 2005;Fortes et al, 2007;Lorenz et al, 2008;Sotin and Tobie, 2008;Tobie et al, 2009;Sohl et al, 2010).…”