Titan has an organic-rich atmosphere and surface with a subsurface liquid water ocean that may represent a habitable environment. In this work, we determined the amount of organic material that can be delivered from Titan's surface to its ocean through impact cratering. We assumed that Titan's craters produce impact melt deposits composed of liquid water that can founder in its lower-density ice crust and estimated the amount of organic molecules that could be incorporated into these melt lenses. We used known yields for HCN and Titan haze hydrolysis to determine the amount of glycine produced in the melt lenses and found a range of possible flux rates of glycine from the surface to the subsurface ocean. These ranged from 0 to 1011 mol/Gyr for HCN hydrolysis and from 0 to 1014 mol/Gyr for haze hydrolysis. These fluxes suggest an upper limit for biomass productivity of ∼103 kgC/year from a glycine fermentation metabolism. This upper limit is significantly less than recent estimates of the hypothetical biomass production supported by Enceladus's subsurface ocean. Unless biologically available compounds can be sourced from Titan's interior, or be delivered from the surface by other mechanisms, our calculations suggest that even the most organic-rich ocean world in the Solar System may not be able to support a large biosphere.

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Associate Editor: Christopher McKay

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Published In

cover image Astrobiology
Volume 24Issue Number 2February 2024
Pages: 177 - 189
PubMed: 38306187


Published online: 20 February 2024
Published ahead of print: 2 February 2024
Published in print: February 2024
Accepted: 1 January 2024
Received: 11 May 2023


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Department of Earth Sciences, The University of Western Ontario, London, Ontario, Canada.
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.
Christophe Sotin
Laboratoire de Planétologie et Géosciences, Nantes Université, Univ Angers, Le Mans Université, CNRS, UMR 6112, Nantes, France.
Rosaly M.C. Lopes
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.
Conor A. Nixon
Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
Antonin Affholder
Department of Ecology and Evolutionary Biology, The University of Arizona, Tucson, Arizona, USA.
Audrey Chatain
Departamento de Física Aplicada, Escuela de Ingeniería de Bilbao, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Bilbao, Spain.
Charles Cockell
UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom.
Kendra K. Farnsworth
NASA Postdoctoral Program Fellow, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
Peter M. Higgins
Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada.
Kelly E. Miller
Southwest Research Institute, San Antonio, Texas, USA.
Krista M. Soderlund
Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA.


Address correspondence to: Catherine Neish, Department of Earth Sciences, The University of Western Ontario, London, ON N6A 5B7, Canada [email protected]

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This research was supported by the International Space Science Institute (ISSI) in Bern, through ISSI International Team project #539 (The habitability of Titan's subsurface water ocean). Catherine Neish also recognizes support from an NSERC Discovery grant. Charles Cockell acknowledges support from the Science and Technology Facilities Council (STFC), grant no. ST/V000586/1. Kelly E. Miller acknowledges support from NASA grant 80NSSC19K0559. Kendra K. Farnsworth was supported by an appointment to the NASA Postdoctoral Program at NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. Krista M. Soderlund acknowledges support by the NASA Astrobiology program grant Oceans Across Space and Time (Grant No. 80NSSC18K1301). Rosaly M.C. Lopes and Michael J. Malaska acknowledge support from the NASA Astrobiology Institute through its JPL-led team entitled Habitability of Hydrocarbon Worlds: Titan and Beyond. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Government sponsorship is acknowledged.

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