Prebiotic Chemistry Insights for Dragonfly: Thermodynamics of Amino Acid Synthesis in Selk Crater on Titan

Saturnian moon Titan presents a compelling testbed for probing prebiotic chemistry beyond early Earth. Impact-generated melt pools provide transient aqueous habitats in an otherwise cryogenic environment.

We use Cantera equilibrium models to assess whether mixtures of hydrogen cyanide (HCN), acetylene (C₂H₂), and ammonia (NH₃) can drive amino acid synthesis in Selk-sized craters. Across twenty-one amino acids (twenty proteinogenic plus beta-alanine), NH₃-free systems yield only proline, alanine, and beta-alanine, whereas adding as little as 1% NH₃ (relative to H₂O) renders almost the full suite accessible, with yields peaking at 2% and tapering thereafter.

The NH₃-free alanine result implies alternative pathways beyond classical Strecker or aminonitrile hydrolysis, suggesting acetylene, abundant on Titan but scarce on early Earth, as a plausible feedstock. We identify acrylonitrile (detected on Titan) as a thermodynamically favorable intermediate that can convert to alanine under aqueous conditions in an NH₃-free pathway.

For glycine and alanine production from nitrile hydrolysis, comparison with laboratory kinetics shows that our equilibrium models predict near-complete conversion, while observed rates yield only partial products over weeks. Yet estimated chemical equilibration times (years-centuries) are far shorter than melt lifetimes, supporting plausibility of equilibrium in situ.

These predictions are directly testable with Dragonfly mass spectrometer (DraMS), for which we recommend pre-flight standards to test proline, alanine, beta-alanine, cysteine, and methionine. The first three offer the best chances for amino acid detection regardless of ammonia availability; the latter two offer diagnostic tools for determining the presence of reactive sulfur in post-impact Titan ponds.

Ishaan Madan, Ben K.D. Pearce

Comments: Note that there is an appendix after the references of the main manuscript
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Chemical Physics (physics.chem-ph); Biomolecules (q-bio.BM)
Cite as: arXiv:2511.09636 [astro-ph.EP] (or arXiv:2511.09636v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2511.09636
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Related DOI:
https://doi.org/10.3847/PSJ/ae1c18
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Submission history
From: Ishaan Madan
[v1] Wed, 12 Nov 2025 19:00:04 UTC (1,188 KB)
https://arxiv.org/abs/2511.09636

Astrobiology,