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Published January 15, 2014 | Supplemental Material
Journal Article Open

The formation of infilled craters on Mars: Evidence for widespread impact induced decompression of the early martian mantle?

Abstract

Flat-floored craters have long been recognized on Mars with early work hypothesizing a sedimentary origin. More recently, high-resolution thermal inertia measurements show that these craters contain some of the rockiest materials on the planet, inconsistent with poorly consolidated sedimentary materials. In this study, the distribution, physical properties (morphology and thermal inertia), and composition of these craters are thoroughly investigated over the entire planet. The majority of the ∼2800 rocky crater floors identified are concentrated in the low albedo (0.1–0.17), cratered southern highlands. These craters were infilled at ∼3.5 Ga and are associated with the highest thermal inertia values and some of the most mafic materials identified on the planet. Although several processes may have led to the formation of the crater floors, the most likely scenario is volcanic infilling through fractures created by the impact event. The primitive magma source directly results from decompression melting of the martian mantle by the removal of the crustal material excavated by the impactor. Volcanic infilling of craters by decompression melting appears to only have occurred in early martian history when the lithosphere was still relatively thin and the thermal gradient was high. This process was widespread and responsible for the eruption of significant volumes of primitive material, inside and likely outside of craters. Impact induced decompression melting of the martian mantle accounts for the unusual infilling of martian craters and is a widespread planetary process that has gone previously undocumented.

Additional Information

© 2013 Elsevier Inc. Received 21 February 2013. Revised 26 September 2013. Accepted 2 October 2013. Available online 12 October 2013. The authors thank J. Brian Balta and an anonymous reviewer for comments that significantly improved the quality of this manuscript. We also thank Robin Fergason for providing the THEMIS thermal inertia images used to create small-scale quantitative mosaics, George Bergantz for helpful discussions, as well as the JMARS software development team (http://jmars.asu.edu), THEMIS mission planners, and support staff for targeting regions of interest and helpful discussions. We also thank the tireless efforts of Reid Landeen and Priya Challa who counted more than 50,000 craters for this study. This work was funded by the 2001 Mars Odyssey THEMIS project.

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