Preserved morphologies of an ancient dune field - the first identification of negative casts of "ghost dunes" on Mars

Dune fields are ubiquitous across the surface of modern Mars, and evidence suggests that aeolian activity has been pervasive for much of Mars' geologic history. Several examples of preserved ancient dune strata have now been studied, but few of these preserve the morphologies of ancient dunes, let alone the variability within the dune field. In this work, we present analysis of two fields of pits on Mars interpreted to be the remnants of partially buried dunes. Flooded by lava or covered by sediments to approximately half their height, these ancient "ghost dunes" were immobilized and eventually transported away, leaving negative topographic casts or pits outlining the morphologies of the ancient dunes. We present new imaging over these putative ancient dunes and discuss in detail the proposed formation mechanism of partial burial and excavation.