  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.
