Candidate volcanic and impact-induced ice depressions on Mars

We present an analysis of two concentrically-fractured depressions on Mars, one in northern Hellas and the second in Galaxias Fossae. Volumetric measurements indicate that ∼2.4 km 3 and ∼0.2 km 3 of material was removed in order to form the North Hellas and Galaxias depressions. The removed material is inferred to be predominantly water ice. Calorimetric estimates suggest that up to ∼10 3 –10 5 m 3 of magma would have been required to melt/sublimate such a volume of ice under an ice/magma interaction scenario. This process would lead to subsidence and cracking of the surface, which could produce the observed concentric fracture (crevasse-like) morphology. While the Galaxias Fossae landform morphology is consistent with an impact origin, the large volume of removed material in North Hellas is less consistent with an impact origin and is interpreted to have resulted from volcanic melting of ice. The possibility of liquid water formation during or subsequent to volcanism or an impact could generate locally-enhanced habitable conditions, making these features tantalizing geological and astrobiological exploration targets. © 2016 Elsevier Inc. All rights reserved.