FRACTURE SYSTEMS AS TARGETS OF ASTROBIOLOGICAL INTEREST: MARS 2020 MISSION IN JEZERO CRATER

Jezero crater (18.8° N; 76.6° E) is an approximately 48 km diameter crater that lies northeast of the Syrtis Major volcanic region, near the margin of Isidus Planitia. As the landing site for the Mars2020 mission, Jezero crater will be increasingly examined in terms of potential astrobiological targets. Two distinct targets have been noted to be of high astrobiological interest: phyllosilicate-bearing strata of the western and northern fans that represent water-lain sedimentary materials; and deposits that show a spectral signal of Mg-carbonate that may reflect mineral precipitation from circum-neutral fluids. Here we focus on an additional target of potential astrobiological significance: a potentially mineralized fracture system that occurs within the crater floor and may represent migration of subsurface fluids within the crater

Two distinct sets of fractures are exposed within Jezero crater. The first occurs exclusively within smooth, dark-toned crater floor material. These fractures occur primarily as hierarchical polygons that are typically unoriented, except near the edges of dark-toned crater floor material, suggesting that fracture formation is related to tensional stresses within dark-toned materials. A second fracture system is represented by a series of unoriented, but often straight fractures that are exposed in erosional relief above dark-toned crater floor materials. This fracture system provides convincing evidence of fluid flow; erosional relief at edges of fractures suggests preferential mineralization (or alteration) of bedrock adjacent to fractures. Critically, these fractures do not extend beyond the edges of the dark-toned materials, suggesting that their formation may have been tied directly to emplacement of dark-toned, crater floor materials. Because mineralization associated with fractures has high potential for preserving biosignatures from either habitable surface and subsurface environments, detailed investigation of such fracture systems is critical to constraining both the origin of the fracture systems, and the timing and origin of potential fluid events that played a role in the preservation of these features.