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Phyllosilicates exposed by Nirgal Vallis
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Phyllosilicates exposed by Nirgal Vallis

Acquired Date: September 16, 2008
Release Date: April 24, 2017
Latitude: 29.25 S
Longitude: 38.25 W
Keywords: Channel, Layered Mineral, Phyllosilicate minerals, Southern Highlands
Parameters: BD1900R/BD1950 (H2O), D2200 (Al-OH minerals), D2300 (Fe-Mg phyllosilicates)

A mosaic of CRISM images cover Nirgal Vallis, a valley system in northwestern Noachis Terra region of Mars. The steep valley walls expose a layer of iron-magnesium phyllosilicates (magenta) just beneath the Noachian-aged basaltic surface. Phyllosilicates are clay and clay-like minerals formed by interaction of rock with liquid water. The phyllosilicates here are rich in iron and magnesium, a type that is common in the southern highlands but not usually found as a discreet layer as observed in this region.



A mosaic of CRISM images cover Nirgal Vallis, a valley system in northwestern Noachis Terra region of Mars. The steep valley walls expose a layer of iron-magnesium phyllosilicates (magenta) just beneath the Noachian-aged basaltic surface. Phyllosilicates are clay and clay-like minerals formed by interaction of rock with liquid water. The phyllosilicates here are rich in iron and magnesium, a type that is common in the southern highlands but not usually found as a discreet layer as observed in this region.

It has been suggested that the phyllosilicate layer exposed by Nirgal Vallis was produced by pedogenesis, or the process of weathering rocks into soils by rainwater or melted snow. However, the flow of groundwater through a layer of brecciated bedrock or volcanic ash could also have created the observed phyllosilicates. Numerical groundwater models predict that the uplift of the Tharsis plateau to the west would allow water to flow through the subsurface and emerge on the surface in this area.

The CRISM mosaic shown is made up of (from north to south): FRT00016BEE (acquired February 22, 2010), FRT0000C875 (September 16, 2008), FRT00018922 (May 5, 2010) and FRT00018EBA (May 22, 2010).

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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