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Phyllosilicates exposed by Her Desher Vallis
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Phyllosilicates exposed by Her Desher Vallis

Acquired Date: January 30, 2008
Release Date: April 10, 2017
Latitude: 25.00 S
Longitude: 48.00 W
Keywords: Channel, Fracture/Faults, Layered Mineral, Phyllosilicate minerals, Southern Highlands
Parameters: BD1900R/BD1950 (H2O), D2200 (Al-OH minerals), D2300 (Fe-Mg phyllosilicates)

This mosaic of CRISM images covers Her Desher Vallis, a valley system in northwestern Noachis Terra region of Mars. The steep valley walls expose the presence of a layer of iron-magnesium (magenta) phyllosilicates just beneath the Noachian-aged basaltic surface. Phyllosilicates are clay and clay-like minerals formed by chemical reactions with liquid water. The phyllosilicates here are rich in iron and magnesium. Phyllosilicates with this composition formed by reaction of basaltic igneous rocks with water, without flushing of soluble elements, and they are common in the southern highlands. Other hydrated minerals (blue) are also present.



This mosaic of CRISM images covers Her Desher Vallis, a valley system in northwestern Noachis Terra region of Mars. The steep valley walls expose the presence of a layer of iron-magnesium (magenta) phyllosilicates just beneath the Noachian-aged basaltic surface. Phyllosilicates are clay and clay-like minerals formed by chemical reactions with liquid water. The phyllosilicates here are rich in iron and magnesium. Phyllosilicates with this composition formed by reaction of basaltic igneous rocks with water, without flushing of soluble elements, and they are common in the southern highlands. Other hydrated minerals (blue) are also present.

Northwest Noachis Terra, a highland volcanic plain, is bound by Coprates and Eos Chasma to the north, Thaumasia Planum to the west, the Argyre basin to the south, and Uzboi Vallis, a major Martian valley system, to the east. Her Desher Vallis is an isolated valley in NW Noachis that does not obviously connect to any outlet, such as a crater or another valley system. Instead it abruptly terminates against an east-west trending fault system. It has been suggested that the phyllosilicate layer exposed by Her Desher was produced by pedogenesis, the process of weathering of volcanic rocks into soils by rainwater or melted snow. However, the flow of groundwater through a layer of fractured bedrock or volcanic ash could also have yielded the observed phyllosilicates. Computer models of groundwater flow have suggested that the uplift of the nearby Tharsis plateau would allow for both groundwater flow and breakout in NW Noachis Terra.

The CRISM mosaic shown is made up of (from west to east): FRT000137AD (acquired July 4, 2009), FRT0001649E (February 4, 2010), FRT0001882F (May 3, 2010), FRT000168C0 (February 15, 2010), FRT00016FA5 (March 4, 2010), FRT00018CA4 (May 14, 2010), FRT00018057 (April 17, 2010), and HRL00009B61 (January 30, 2008).

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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