Duration and Rapid Shutdown of Mars Lake-forming Climates Explained by Methane Bursts

Build-up of relatively young (<∼3.6 Ga) deltas and alluvial fans on Mars required lakes to persist for >3 Kyr (assuming dilute flow), but the watersheds’ little-weathered soils indicate a climate history that was >99% dry.

The lake-forming climates’ trigger mechanism remains unknown. Here we show that these intermittency constraints, while inconsistent with many previously-proposed triggers for lake-forming climates, are consistent with a novel CH4-burst mechanism. Chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize CH4 clathrate. For past clathrate hydrate stability zone occupancy fractions >∼0.2, we show that CH4(±C2H6) builds up to levels whose radiative forcing (>15 W/m2, plus feedbacks) is sufficient to modulate lake-forming climates. Such occupancy fractions are consistent with CH4+C2H6 production by >3 Ga water-rock reactions.

Sub-lake CH4 destabilization provides positive feedback. UV-limited CH4 photolysis curtails individual lake-forming climates to <106 yr duration, consistent with data. Our results show how a warmer early Mars can undergo intermittent excursions to a warm, wet climate state. Edwin S. Kite, Colin Goldblatt, Peter Gao, David P. Mayer
(Submitted on 6 Nov 2016)

Comments: Submitted
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1611.01717 [astro-ph.EP] (or arXiv:1611.01717v1 [astro-ph.EP] for this version)
Submission history
From: Edwin Kite
[v1] Sun, 6 Nov 2016 01:58:51 GMT (4689kb)
https://arxiv.org/abs/1611.01717