Climate optimum on Mars initiated by atmospheric collapse

Edwin S. Kite, Michael A. Mischna, Peter Gao, Yuk L. Yung
(Submitted on 25 Sep 2017)

The progressive drying-out of Mars’ surface was punctuated by a dramatic transient increase in fluvial erosion around the Noachian-Hesperian boundary (∼3.7 Ga). Standard explanations of this climate optimum appeal to volcano- or impact-triggered climates and imply that individual runoff episodes were brief, apparently inconsistent with evidence for persistent runoff. We examine a scenario in which the duration, intensity and uniqueness of the Noachian-Hesperian climate optimum result from degassing of CH4-clathrate consequent to atmospheric collapse. Atmospheric collapse causes low-latitude surface water ice to sublimate away, depressurizing and thus destabilizing CH4 clathrate in subglacial pore space. Subsequent atmospheric re-inflation leads to warming that further destabilizes CH4 clathrate. CH4-induced warming is efficient, permitting strong positive feedbacks, and possibly raising Mars into a climate optimum. The optimum is brought to a close by photochemical destruction of CH4 or by a new atmospheric collapse, and drawdown of the CH4-clathrate reservoir prevents recurrence. This scenario predicts a 105-106 yr climate optimum, transient connections between the deep hydrosphere and the surface, mud volcanism, and strong surface weathering, all of which are consistent with recent observations. Crustal hydrothermal circulation very early in Mars history could yield CH4 that would be incorporated into clathrate on approach to the cold surface. The scenario explains why regional watershed integration on Mars occurred relatively late and apparently only once, and suggests that the contrasts between Noachian versus Hesperian climate-sensitive deposits on Mars correspond to a transition from a never-collapsed atmosphere to a collapse-prone climate, ultimately driven by slow loss of CO2 to space.

Comments:    in review
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1709.08302 [astro-ph.EP] (or arXiv:1709.08302v1 [astro-ph.EP] for this version)
Submission history
From: Edwin Kite
[v1] Mon, 25 Sep 2017 03:25:14 GMT (5726kb)
https://arxiv.org/abs/1709.08302