Growth and form of the mound in Gale Crater, Mars: Slope-wind enhanced erosion and transport

TL;DR

This study proposes a new model for Gale Crater's sedimentary mound formation on Mars, emphasizing wind-driven erosion and deposition processes rather than water-related hypotheses, supported by stratigraphic measurements.

Contribution

The paper introduces a wind-topography feedback model explaining mound growth and shape, challenging previous water-based formation hypotheses.

Findings

Stratigraphic data shows outward dips inconsistent with evaporitic, lacustrine, or fluvial origins.

The mound's current form is near its maximum extent, not just erosional remnants.

Wind-driven processes dominate sediment deposition and erosion in mound formation.

Abstract

Ancient sediments provide archives of climate and habitability on Mars. Gale Crater, the landing site for the Mars Science Laboratory (MSL), hosts a 5 km high sedimentary mound. Hypotheses for mound formation include evaporitic, lacustrine, fluviodeltaic, and aeolian processes, but the origin and original extent of Gale's mound is unknown. Here we show new measurements of sedimentary strata within the mound that indicate ~3 degree outward dips oriented radially away from the mound center, inconsistent with the first three hypotheses. Moreover, although mounds are widely considered to be erosional remnants of a once crater-filling unit, we find that the Gale mound's current form is close to its maximal extent. Instead we propose that the mound's structure, stratigraphy, and current shape can be explained by growth in place near the center of the crater mediated by wind-topography feedbacks. Our model shows how sediment can initially accrete near the crater center far from crater-wall katabatic winds, until the increasing relief of the resulting mound generates mound-flank slope-winds strong enough to erode the mound. Our results indicate mound formation by airfall-dominated deposition with a limited role for lacustrine and fluvial activity, and potentially limited organic carbon preservation. Morphodynamic feedbacks between wind and topography are widely applicable to a range of sedimentary mounds and ice mounds across the Martian surface, and possibly other planets.