EVIDENCE FOR VOLCANISM IN MARTIAN FLOOR-FRACTURED CRATERS FROM THE MARS RECONNAISSANCE ORBITER CONTEXT CAMERA

Floor-fractured craters (FFCs) have been observed on the Moon and Mars, and potentially on Mercury, Venus, and Earth. Lunar FFCs display surface deformation features similar to that seen over terrestrial laccoliths. They are also distributed along the margins of the lunar mare; hence their formation is thought to be the result of igneous intrusions beneath the crater floor, causing doming of the floor leading to the formation of. Volcanic flows have been observed in many lunar FFCs and are thought to have formed in regions and times when large subsurface magma chambers and/or surface mare/lava plains were emplaced. Analysis of martian FFCs by Bamberg et al. [2014] supports an intrusive volcanic origin for fracturing in at least some cases, possibly in combination with ground ice and/or groundwater. Here, observations of dark-toned flows appearing to be sourced from fractures within martian FFCs in close proximity to Valles Marineris and the associated chaos regions imaged by the Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) are presented. The flows are best visible in images acquired between L_s ~25–70°. The dark-toned flows have retained more small (sub-kilometer) craters than the surrounding plateau material, suggesting the dark material is more resistant to erosion. This, paired with the observation that the margins of the flow are not significantly eroded, supports the interpretation that this material is a lava flow as opposed to a mudflow, which would be eroded more readily. The observation of lava flows associated with fractures in some of the FFCs supports the hypothesis that volcanism is involved in their formation. The spatial correlation of FFCs with the chaos terrains potentially supports the suggestion of Sato et al. [2010] that FFCs represent an early stage of chaos terrain formation.

References:

Bamberg, M., R. Jaumann, H. Asche, T. Kneissl, and G. G. Michael (2014), Floor-fractured craters on Mars—Observations and origin, Planet. Space Sci., 98, 146–162.

Sato, H., K. Kurita, and D. Baratoux (2010), The formation of floor-fractured craters in Xanthe Terra, Icarus, 207, 248–264.