The color coding on this composite image of an area about 20 kilometers
(12 miles) wide on Mars is based on infrared spectral information
interpreted as evidence of various minerals present. Carbonate, which is
indicative of a wet and non-acidic history, occurs in very small patches
of exposed rock appearing green in this color representation, such as near
the lower right corner.
The scene is heavily eroded terrain to the west of a small canyon in the
Nili Fossae region of Mars. It was one of the first areas where
researchers on the Compact Reconnaissance Imaging Spectrometer for Mars
(CRISM) science team detected carbonate in Mars rocks. The spectral
information comes from infrared imaging by CRISM, one of six science
instruments on NASA's Mars Reconnaissance Orbiter. That coloring is
overlaid on a grayscale image from the same orbiter's Context Camera.
The uppermost capping rock unit (purple) is underlain successively by
banded olivine-bearing rocks (yellow) and rocks bearing iron-magnesium
smectite clay (blue). Where the olivine is a greenish hue, it has been
partially altered by interaction with water. The carbonate and olivine
occupy the same level in the stratigraphy, and it is thought that the
carbonate formed by aqueous alteration of olivine. The channel running
from upper left to lower right through the image and eroding into the
layers of bedrock testifies to the past presence of water in this region.
That some of the channels are closely associated with carbonate (lower
right) indicates that waters interacting with the carbonate were neutral
to alkaline because acidic waters would have dissolved the carbonate.
Information for the color coding came from CRISM images catalogued as
FRT0000B438, FRT0000A4FC, and FRT00003E12. This composite was made using
2.38-micrometer-wavelenghth data as red, 1.80 micrometer as green and 1.15
micrometer as blue.
The base black-and-white image, acquired at a resolution of 5 meters (16
feet) per pixel, is catalogued as CTX P03_002176_2024_XI_22N283W_070113 by
the Context Camera science team.
NASA's Jet Propulsion Laboratory, a division of the California Institute
of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for the
NASA Science Mission Directorate, Washington. Lockheed Martin Space
Systems, Denver, is the prime contractor for the project and built the
spacecraft. The Johns Hopkins University Applied Physics Laboratory led
the effort to build the CRISM instrument and operates CRISM in
coordination with an international team of researchers from universities,
government and the private sector. Malin Space Science Systems, San Diego,
provided and operates the Context Camera.
