What kept early Mars warm enough for rivers and lakes? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
What kept early Mars warm enough for rivers and lakes?
Plain
About 3.7 billion years ago Mars had river valleys and lakes even though it is farther from a then fainter Sun. Carbon dioxide and water vapour alone do not seem able to warm it enough, so the question is what else did.
Precise · changed · core
Revision 1: For Noachian to early Hesperian Mars (about $3.8\ \text{to}\ 3.5\,\mathrm{Gyr}$ ago, insolation $\sim 0.32\,S_0$ relative to modern Earth) determine whether surface runoff required sustained warm conditions (mean $T$ above $273\,\mathrm{K}$) or episodic warming, and identify the forcing: CO2-H2 or CO2-CH4 collision-induced absorption, cirrus clouds, impacts or volcanic outgassing. An answer specifies atmospheric composition, pressure and duration consistent with valley-network and lake-sediment volumes and with surviving carbonate inventories.
Revision 2: For Noachian to early Hesperian Mars (about $3.8\ \text{to}\ 3.5\,\mathrm{Gyr}$ ago, insolation $\sim 0.32\,S_0$ relative to modern Earth) determine whether surface runoff required sustained warm conditions (mean $T$ above $273\,\mathrm{K}$) or episodic warming, and identify the forcing: $\mathrm{CO_2}$-$\mathrm{H_2}$ or $\mathrm{CO_2}$-$\mathrm{CH_4}$ collision-induced absorption, cirrus clouds, impacts or volcanic outgassing. An answer specifies atmospheric composition, pressure and duration consistent with valley-network and lake-sediment volumes and with surviving carbonate inventories.
Settled by · changed · core
Revision 1: A climate scenario whose required H2 or CH4 sources, surface pressure and warm-period duration match sediment volumes and the measured carbonate and atmospheric-loss record.
Revision 2: A climate scenario whose required $\mathrm{H_2}$ or $\mathrm{CH_4}$ sources, surface pressure and warm-period duration match sediment volumes and the measured carbonate and atmospheric-loss record.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
contested
Status note
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Posed since
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