The stratigraphy and history of Mars’ northern lowlands through mineralogy of impact craters: A comprehensive survey

1Lu Pan, 1,2Bethany L. Ehlmann, 3John Carter, 4Carolyn M. Ernst
Journal of Geophysical Research Planets (in Press) Link to Article [DOI: 10.1002/2017JE005276]
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
3Institut d’Astrophysique Spatiale, Orsay, France
4The John Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
Published by arrangement with John Wiley & Sons

The basin-filling materials of the northern lowlands, which cover ~1/3 of Mars’ surface, record the long-term evolution of Mars’ geology and climate. The buried stratigraphy was inferred through analyses of impact crater mineralogy, detected using data acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Examining 1045 impact craters across the northern lowlands, we find widespread olivine and pyroxene and diverse hydrated/hydroxylated minerals, including Fe/Mg smectite, chlorite, prehnite, and hydrated silica. The distribution of mafic minerals is consistent with infilling volcanic materials across the entire lowlands (~1–4⋅107 km3), indicating a significant volume of volatile release by volcanic outgassing. Hydrated/hydroxylated minerals are detected more frequently in large craters, consistent with the scenario that the hydrated minerals are being excavated from deep basement rocks, beneath 1-2 km thick mafic lava flows or volcaniclastic materials. The prevalences of different types of hydrated minerals are similar to statistics from the southern highlands. No evidence of concentrated salt deposits has been found, which would indicate a long-lived global ocean. We also find significant geographical variations of local mineralogy and stratigraphy in different basins (geological provinces), independent of dust cover. For example, many hydrated and mafic minerals are newly discovered within the polar Scandia region (> 60°N), and Chryse Planitia has more mafic mineral detections than other basins, possibly due to a previously unrecognized volcanic source.

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