¹Joshua L. Bandfield
American Mineralogist Link to Article [DOI: 10.2138/am-2017-5955]
¹Space Science Institute, Boulder, Colorado 80301, U.S.A.
Copyright: The Mineralogical Society of America

The Mars Exploration Rover “Spirit” provided us with a serendipitous opportunity to traverse a section of the ancient martian crust, acquiring a trove of imaging, geochemical, and mineralogical measurements along the way. This small window looking out on the Noachian period (>3.7 Ga), dubbed the Columbia Hills, pokes out from the younger, volcanically resurfaced floor of Gusev Crater. It was our first detailed look at early Mars, a time when liquid water appears to have played a much more prominent role in shaping and modifying the planet than later in its history.

The abundance of rocks that appear to be snapshots from early in the history of Mars is a luxury compared to the rarity and inevitable metamorphic overprinting of Hadean and early Archean samples from Earth. However, few planetary surfaces of this age anywhere in the solar system escape the disruption caused by impacts. In this sense, it is difficult to identify the geologic context of any given sample or series of samples. Although what appears to be an outcrop of a draping volcaniclastic unit in the Columbia Hills may still be in place, it is also possible for it to have been highly …

^1,2Honglei LIN, ¹Xia ZHANG
Icarus (in Press) Link to Article [http://dx.doi.org/10.1016/j.icarus.2017.01.019]
¹State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Science, Beijing 100101,China
¹University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier

The hydrous minerals on Mars preserve records of potential past aqueous activity. Quantitative information regarding mineralogical composition would enable a better understanding of the formation processes of these hydrous minerals, and provide unique insights into ancient habitable environments and the geological evolution of Mars. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has the advantage of both a high spatial and spectral resolution, which makes it suitable for the quantitative analysis of minerals on Mars. However, few studies have attempted to quantitatively retrieve the mineralogical composition of hydrous minerals on Mars using visible-infrared (VISIR) hyperspectral data due to their distribution characteristics (relatively low concentrations, located primarily in Noachian terrain, and unclear or unknown background minerals) and limitations of the spectral unmixing algorithms. In this study, we developed a modified sparse unmixing (MSU) method, combining the Hapke model with sparse unmixing. The MSU method considers the nonlinear mixed effects of minerals and avoids the difficulty of determining the spectra and number of endmembers from the image. The proposed method was tested successfully using laboratory mixture spectra and an Airborne Visible Infrared Imaging Spectrometer (AVIRIS) image of the Cuprite site (Nevada, USA). Then it was applied to CRISM hyperspectral images over Gale crater. Areas of hydrous mineral distribution were first identified by spectral features of water and hydroxyl absorption. The MSU method was performed on these areas, and the abundances were retrieved. The results indicated that the hydrous minerals consisted mostly of hydrous silicates, with abundances of up to 35%, as well as hydrous sulfates, with abundances ≤10%. Several main subclasses of hydrous minerals (e.g., Fe/Mg phyllosilicate, prehnite, and kieserite) were retrieved. Among these, Fe/Mg- phyllosilicate was the most abundant, with abundances ranging up to almost 30%, followed by prehnite and kieserite, with abundances lower than 15%. Our results are consistent with related research and in situ analyses of data from the rover Curiosity; thus, our method has the potential to be widely used for quantitative mineralogical mapping at the global scale of the surface of Mars.