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Chlorite on the Oenotria Scopuli
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Chlorite on the Oenotria Scopuli

Acquired Date: March 2, 2008
Release Date: August 27, 2020
Latitude: 11.72 S
Longitude: 78.89 E
Keywords: Crater Interior/Rim/Ejecta, Ridges, Hydrated Mineral, Phyllosilicate minerals
Parameters: BD2290 (Mg/Fe-OH minerals), BD2355 (Chlorite/Prehnite/Pumpellyite/Illite), D2300 (Fe-Mg phyllosilicates)

Tyrrhena Terra is a large, Noachian-aged cratered highland province on Mars, between the Isidis and Hellas basins. CRISM image A33C shows an unnamed crater that impacted a hill in this region, located on the Oenotria Scopuli, a set of irregular scarps.



Tyrrhena Terra is a large, Noachian-aged cratered highland province on Mars, between the Isidis and Hellas basins. CRISM image A33C shows an unnamed crater that impacted a hill in this region, located on the Oenotria Scopuli, a set of irregular scarps.

The parameter image is a red-green-blue composite where R=BD2355, G=D2300, B=BD2290, meant to highlight cation compositions of hydroxylated minerals including Fe/Mg-phyllosilicate. It suggests that the interior of the crater hosts a mixture of a mixture of smectite and chlorite, as shown by the green. Conversely, the yellow streak and faint red in the crater’s ejecta blanket (the debris thrown out of the crater by the impact that created it) indicate a composition of chlorite and epidote. Smectite and chlorite are phyllosilicates, and epidotes are sorosilicates. While all of these minerals form in the presence of liquid water, some also require elevated temperatures like that found in metamorphic or hydrothermal settings. This may indicate that these materials were once deeply buried before being unearthed by the impact, and originally formed much earlier in Mars’ history. In fact, these minerals may have been relocated within the crust multiple times, only to finally be brought to the surface by this relatively small crater.

The Noachian period (4.1-3.7 billion years ago) was a time period characterized by impacts, volcanic activity, and precipitation, all processes that are inducive to the chemical alteration of many rocks. Data suggests that the surface of this region in Tyrrhena Terra is from the late Noachian period; thus, the buried minerals could be early or middle Noachian. The increased presence of water could have resulted in the synthesis of phyllosilicates, which were later covered by new, non-hydrated layers of rock.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument also tracks seasonal variations in dust and ice aerosols in the Martian atmosphere, and water content in surface materials — leading to new understanding of the climate.

Credit: NASA/JPL/JHUAPL

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