Fresh exposures of hydrous Fe‐bearing amorphous silicates on Mars. Issue 24 (30th December 2014)

• Record Type: Journal Article
• Authors: Weitz, Catherine M.; Bishop, Janice L.; Baker, Leslie L.; Berman, Daniel C.
• Is Part Of: Geophysical research letters. Volume 41:Issue 24(2014:Dec.)
• Page Start: 8744
• Page End: 8751
• Publication Date: 2014-12-30
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2014GL062065
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>We have discovered relatively fresh exposures of a hydrated, amorphous material along the wall rock slopes in Coprates Chasma, Mars. Visible and near‐infrared reflectance spectra extracted from the deposits exhibit broad absorptions around 1.42, 1.94, and 2.25 µm that are most consistent with laboratory spectra of nanophase hydrated Fe‐rich allophane and Fe‐rich opal. The three absorptions, especially the 1.4 µm band, have the strongest hydration signatures yet detected on Mars by orbital data, suggesting high‐water content material that is relatively fresh and has not altered or lost water since its formation or exposure. Age dating from crater size‐frequency distributions of the Fe‐rich allophane/opal deposits yields ages of ~50–100 Myr, consistent with a young exposure time and minimal time for dehydration. Either the Fe‐rich allophane/opal represents an older material already contained within the wall rock that has been more recently exposed, or it represents a younger material formed during more recent aqueous activity.</p> </abstract>