Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars

TL;DR

This paper proposes that methane bursts triggered by obliquity-driven destabilization of methane clathrates could explain intermittent lake-forming climates on post-Noachian Mars, aligning with geological and atmospheric evidence.

Contribution

It introduces a novel methane burst scenario driven by obliquity changes as a mechanism for episodic warm climates on early Mars, supported by numerical simulations.

Findings

Methane can reach levels sufficient for lake formation during outgassing events.

Photochemical methane destruction limits lake-forming periods to less than a million years.

Obliquity-driven destabilization of methane clathrates is consistent with geological evidence.

Abstract

Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluvio-lacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand years (assuming dilute flow). But the lake watersheds' little weathered soils indicate a largely dry climate history, with intermittent runoff events. Here we show that these observational constraints, while inconsistent with many previously-proposed triggers for lake-forming climates, are consistent with a methane burst scenario. In this scenario, chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate. Using numerical simulations, we find that outgassed methane can build up to atmospheric levels sufficient for lake forming climates, for past clathrate hydrate stability zone occupancy fractions >0.04. Such occupancy fractions are consistent with methane production by water-rock reactions due to hydrothermal circulation on early Mars. We further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake-forming climates to less than a million years, consistent with observations. We conclude that methane bursts represent a potential pathway for intermittent excursions to a warm, wet climate state on early Mars.