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Geology topics

J.A. McGovern

Publications and source records attributed to J.A. McGovern.

2 recordsLinked to original sources

Compact Reconnaissance Imaging Spectrometer for Mars investigation and data set from the Mars Reconnaissance Orbiter's primary science phase

The part of the Compact Reconnaissance Imaging Spectrometer (CRISM) for Mars investigation conducted during the Mars Reconnaissance Orbiter's (MRO's) primary science phase was a comprehensive investigation of past aqueous environments, structure of the planet's crust, past climate, and current meteorology. The measurements to implement this investigation include over 9500 targeted observations of surface features taken at spatial resolutions of better than 40 m/pixel, monitoring of seasonal variations in atmospheric aerosols and trace gases, and acquisition of a 200 m/pixel map covering over 55% of Mars in 72 selected wavelengths under conditions of relatively low atmospheric opacity. Key results from these data include recognition of a diversity of aqueous mineral-containing deposits, discovery of a widespread distribution of phyllosilicates in early to middle Noachian units, the first definitive detection of carbonates in bedrock, new constraints on the sequence of events that formed Hesperian-aged, sulfate-rich layered deposits, characterization of seasonal polar processes, and monitoring of the 2007 global dust event. Here we describe CRISM's science investigations during the Primary Science Phase, the data sets that were collected and their calibration and uncertainties, and how they have been processed and made available to the scientific community. We also describe the ongoing investigation during MRO's extended science phase. Copyright 2009 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗

Hydrated silicate minerals on Mars observed by the Mars Reconnaissance Orbiter CRISM instrument

Phyllosilicates, a class of hydrous mineral first definitively identified on Mars by the OMEGA (Observatoire pour la Mineralogie, L’Eau, les Glaces et l’Activitié) instrument 1 , 2 , preserve a record of the interaction of water with rocks on Mars. Global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy (Fe/Mg and Al smectite clays). This was interpreted to indicate that phyllosilicate formation occurred during the Noachian (the earliest geological era of Mars), and that the conditions necessary for phyllosilicate formation (moderate to high pH and high water activity 3 ) were specific to surface environments during the earliest era of Mars’s history 4 . Here we report results from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) 4 of phyllosilicate-rich regions. We expand the diversity of phyllosilicate mineralogy with the identification of kaolinite, chlorite and illite or muscovite, and a new class of hydrated silicate (hydrated silica). We observe diverse Fe/Mg-OH phyllosilicates and find that smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. Stratigraphic relationships in the Nili Fossae region show olivine-rich materials overlying phyllosilicate-bearing units, indicating the cessation of aqueous alteration before emplacement of the olivine-bearing unit. Hundreds of detections of Fe/Mg phyllosilicate in rims, ejecta and central peaks of craters in the southern highland Noachian cratered terrain indicate excavation of altered crust from depth. We also find phyllosilicate in sedimentary deposits clearly laid by water. These results point to a rich diversity of Noachian environments conducive to habitability.

Nature↗