High Resolution and Low Risk
CRISM is a visible-infrared imaging spectrometer
with a scannable field of view. CRISM can cover wavelengths from 370
to 3,920 nanometers (nm) at 6.55 nm/channel - meaning the CRISM team
will be able to identify a broad range of minerals on the Martian
CRISM's high spatial resolution (18 meters/pixel at 300 kilometers altitude)
will reveal deposits as small as house-sized outcrops. CRISM will make
thousands of targeted observations at geometries needed for analysts
to separate and characterize Mars' surface and atmosphere.
To control cost and reduce risk, CRISM draws extensively upon the electronics
and design of imaging technology developed for the CONTOUR
comet-study spacecraft and MESSENGER
'Seeing' the Surface
Once in orbit, CRISM's investigations begin
with sunlight reflected off the Martian surface. CRISM breaks this
light into a spectrum, from which it measures 544 colors. The wide
range of colors helps CRISM determine the mineralogy of the surface.
CRISM's thin rectangular field of view measures a region about 18 meters
(60 feet) wide and 10.8 kilometers (6.7 miles) long, if Mars Reconnaissance
Orbiter is about 300 kilometers (186 miles) above the planet. As the
orbiter flies over a given area, CRISM's scanning mechanism tracks a
region on the surface and slowly sweeps the field of view across it.
CRISM only needs 3 minutes to map several hundred
The instrument's capability to measure so many colors of light makes
it possible to identify most common minerals by their habits of preferentially
absorbing light of different wavelengths. This powerful technique has
been used for decades to study the Red Planet. For example, the map
at right was made from only three colors (green, red and infrared) in
Mars Pathfinder images and shows iron oxide coatings crusted on rocks.
CRISM's key investigation sites include smooth interiors of ancient
craters that may have been filled in by lakes, volcanic regions and
crustal sections exposed in steep cliffs.