2011 Annual Science Report
NASA Jet Propulsion Laboratory - Titan Reporting | SEP 2010 – AUG 2011
Task 3.5.2 Energetics of Titan Life
Thermochemical and dynamic modeling is being used to provide improved constraints on the available chemical energy and trace element fluxes to facilitate potential life on the surface of Titan.
In collaboration with other Co-Investigators, Co-Investigator David Grinspoon has been studying the energetics of the acetylene-hydrogen system and other plausible metabolic pathways for putative Titanian life. In the presence of molecular hydrogen (H2), acetylene reacts exothermally to produce methane:
C2H2 + 3H2 → 2CH4 (1)
The energy yield of this reaction is 107.7 kJ/mol (ΔG = –107.7 kJ/mol or –25.7 kcal/mol) under standard conditions, and about 100 kJ/mol under Titan’s surface conditions. He has previously published an analysis of the energetic potential for this reaction on the surface of Titan and has now begun using Cassini results to inventory and examine the metabolic potential of other energetic organic condensates on the surface of Titan, such as propane, hydrogen cyanide, cyanoacetylene and cyanogen.
In addition, with Co-Investigator Steve Benner, he analyzed infall to the Titan system of both interplanetary and circum-saturnian dust and ice particles, to establish limiting exogenic fluxes of several elements, such as germanium and oxygen that may be important in facilitating potential Titanian metabolisms. Benner has identified some interesting possible chemical bases for life in liquid methane, but finds that they may depend on the supply of some relatively rare (in terms of cosmic abundance) elemental species, such as germanium. Grinspoon has been adopting the formalism developed by Spahn et al. (2006) to interpret the Cassini dust measurements to make predictions of the limiting external fluxes of some of these potentially biologically important species.