From: NASA Mars Reconnaissance Orbiter CRISM
Posted: Sunday, May 6, 2007
This image shows one of the first regions of Mars measured after CRISM's cover was opened.
CRISM takes images in two basic formats. The first format is a "targeted image" about 10 kilometers by 10 kilometers (about 6 miles by 6 miles), at about 18 meters (60 feet) per pixel, in 544 colors covering 0.36-3.92 micronmeters. The second format is a lower-resolution strip 10 kilometers (6 miles) wide and thousands of kilometers long, at 200 meters (660 feet) per pixel, in 72 colors. Many thousands of these "multispectral survey" strips are used to build a global map.
The image is part of the second multispectral survey strip, taken at 22:36 UTC (6:36 p.m. EDT) on Sept. 27, 2006. Only minimal processing of the data has been done at this early point in the Mars Reconnaissance Orbiter's mission. The strip crosses part of the north polar region named Olympia Undae, and stretches between 76.7 north latitude, 141.9 east longitude and 85.5 north, 115.8 east. From the top, the northern end of the image crosses layers of dusty and clean ice in the north polar cap. Moving south the image covers dusty sedimentary deposits, dark sand dunes, and outlying polar ice deposits. (The thumbnail shown here covers only the northernmost part of the full image. Click on the thumbnail above to view the full product.)
This image shows three representations of the 72 colors. The left panel is a nearly true-color composite in which the blue, green, and red planes are 0.44, 0.53, and 0.60 micrometer light ? nearly as the human eye would see. The contrast between the bright ice and dark dunes is so large that the dunes are barely seen. The middle panel is false color constructed from infrared wavelengths just beyond the range of the human eye. The blue, green, and red planes cover 0.80, 0.95, and 1.06 micrometer light. In this rendering of the data the differences between ice- and soil-rich regions are not as apparent because the colors of ice and dust are similar in this wavelength region. The right panel uses 1.15, 1.8, and 2.25 micrometer light in the blue, green and red planes and provides a dramatically different view of the scene. The areas of highest ice content appear in blue, and those with a mix of dust and ice ? most of the scene ? appear yellowish. The dunes are now visible against the ice because of their higher brightness at longer infrared wavelengths, and appear ruddy brown.
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 will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials — leading to new understanding of the climate.
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