Special Department Lecture - Gaia Stucky de Quay (Texas)
Title: Landscape evolution and the early Mars hydroclimate: constraints from paleolake morphologies
Fluvio-lacustrine features on the martian surface attest to a climate that was radically different in the past. Studies of valley networks and paleolakes suggest that long-lived precipitation may have persisted up to 3.7 Ga. However, because climate models have difficulty sustaining a liquid hydrosphere at the surface for more than a few thousand years, it has been hypothesized that multiple cycles of runoff episodes may have characterized the ancient martian climate. Despite the decades-long accumulation of in situ and remote sensing data on surface water modification features, fundamental questions on the nature of Mars’ paleoclimate and its hydrological cycle remain: (1) How much rainfall and/or snowmelt occurred during a given interval of favorable climate?; and (2) How long did these runoff-producing episodes last? Here we combine measurements of 96 open- and closed-basin lakes with simple hydrological balances to constrain catchment-averaged precipitation over a given runoff episode. We include newly identified systems containing both open- and closed-basin lakes—i.e., coupled systems—which provide fully bounded precipitation estimates. We show that, on average, local precipitation was ≳4 m and ≲159 m, and the climate was semi-arid or more humid in certain regions. We integrate these results with existing climate model data to quantitatively derive runoff episode duration, which was likely between 100-10,000 yr and spatially variable. Importantly, these spatio-temporal hydroclimate constraints allow us to test paleoclimate model scenarios, working towards bridging the gap between geological observations and climate theory for early Mars.
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