Gypsum dunes north of Phoenix landing site

In 2005 CRISM's sibling instrument, OMEGA, on board Mars Express, captured data revealing that Olympia Undae's dunes hold sulfate minerals including gypsum. With more than five times the spatial resolution of OMEGA, CRISM has captured greater detail of this region.
The top image reveals the location of CRISM data on a Mars Orbiter Laser Altimeter (MOLA) map. The area from which CRISM data were gathered is roughly 12° north and 11° east of the region where Phoenix recently landed.

The lower left image is an infrared, false-color image that reveals dark colored dunes overlying a lighter, rust-colored substrate. CRISM spectral data (lower right image) shows the region is inundated with sulfates. It also reveals that the darker dune material holds a higher concentration of the water-bearing calcium sulfate mineral gypsum. A full resolution targeted CRISM image taken just five° west of the image above, revealed greater gypsum concentrations along the dunes' crests.

On Earth, gypsum is the most common sulfate mineral and is widely found in sedimentary rocks. It's frequently associated with evaporite salts and is often found as a thick layer beneath halite or rock salt. Although most often associated with evaporites, gypsum can also occur in layers with limestone and shale. Most people are familiar with gypsum in the form of plaster of Paris.

Credit: NASA/JPL/JHUAPL/ASU/USGS.
High resolution image (1.2 MB).

This image of sulfate deposits, including gypsum, in the Olympia Undae region of Mars was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on NASA's Mars Reconnaissance Orbiter at 00:26 UTC on November 18, 2006 near 80° north latitude, 245° east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across.

Source: Johns Hopkins University Applied Physics Laboratory
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