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

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1038/ngeo3033.

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Authors

Edwin Kite , Peter Gao, Colin Goldblatt, Michael A. Mischna, David Mayer , Yuk L. Yung

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.

DOI

https://doi.org/10.31223/osf.io/6quyb

Subjects

Astrophysics and Astronomy, Earth Sciences, Geology, Physical Sciences and Mathematics, The Sun and the Solar System

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Dates

Published: 2019-01-01 09:42

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License

GNU Lesser General Public License (LGPL) 2.1

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