Powerful Mineral Mapper Heads To Mars

Builtby the Johns Hopkins University Applied Physics Laboratory (APL) inLaurel, Md., CRISM is the first visible-infrared spectrometer to fly ona NASA Mars mission. Its primary job: look for the residue of mineralsthat form in the presence of water, the “fingerprints” left byevaporated hot springs, thermal vents, lakes or ponds on Mars whenwater could have existed on the surface.

With unprecedentedclarity, CRISM will map areas on the martian surface down tohouse-sized scales – as small as 60 feet (about 18 meters) across –when the spacecraft is in its average orbit altitude of about 190 miles(more than 300 kilometers).

“CRISM plays a very important role inMars exploration,” says APL’s Dr. Scott Murchie, the instrument’sprincipal investigator. “Our data will identify sites most likely tohave contained water, and which would make the best potential landingsites for future missions seeking fossils or even traces of life onMars.”

Though certain landforms provide evidence that water mayonce have flowed on Mars, Murchie says scientists have little evidenceof sites containing mineral deposits created by long-term interactionbetween water and rock. The NASA Rover Opportunity found evidence forliquid water in Meridian Planum – a large plain near Mars’ equator –but that is only one of many hundreds of sites where future spacecraftcould land.

Peering through a telescope with a 4-inch(10-centimeter) aperture, and with a greater capability to map spectralvariations than any similar instrument sent to another planet, CRISMwill read 544 “colors” in reflected sunlight to detect minerals in thesurface. Its highest resolution is about 20 times sharper than anyprevious look at Mars in infrared wavelengths.

“At infraredwavelengths, rocks that look absolutely the same to human eyes becomevery different,” Murchie says. “CRISM has the capability to take imagesin which different rocks will ‘light up’ in different colors.”

CRISMis mounted on a gimbal, allowing it to follow targets on the surface asthe orbiter passes overhead. CRISM will spend the first half of atwo-year orbit mission mapping Mars at 650-foot (200-meter) scales,searching for potential study areas. Several thousand promising siteswill then be measured in detail at CRISM’s highest spatial and spectralresolution. CRISM will also monitor seasonal variations in dust and iceparticles in the atmosphere, supplementing data gathered by theorbiter’s other instruments and providing new clues about the Martianclimate.

“CRISM will improve significantly on the mappingtechnology currently orbiting Mars,” says CRISM Project Manager PeterBedini, of APL. “We’ll not only look for future landing sites, butwe’ll be able to provide details on information the Mars ExplorationRovers are gathering now. There is a lot more to learn, and after CRISMand the Mars Reconnaissance Orbiter there will still be more to learn.But with this mission we’re taking a big step in exploring andunderstanding Mars.”

As the Mars Reconnaissance Orbiter cruisesto its destination, the CRISM operations team continues to fine-tunethe software and systems it will use to command the instrument andreceive, read, process, and store a wealth of data from orbit – morethan 10 terabytes when processed back on Earth, enough to fill morethan 15,000 compact discs. The spacecraft is set to reach Mars nextMarch, use aerobraking to circularize its orbit, and settle into itsscience orbit by November 2006.

APL, which has built more than150 spacecraft instruments over the past four decades, led the effortto develop, integrate and test CRISM. CRISM’s co-investigators are topplanetary scientists from Brown University, the Jet PropulsionLaboratory, Northwestern University, Space Science Institute,Washington University in St. Louis, University of Paris, the AppliedCoherent Technology Corporation, and NASA’s Goddard Space FlightCenter, Ames Research Center and Johnson Space Center.

The JetPropulsion Laboratory, a division of the California Institute ofTechnology, Pasadena, manages the Mars Reconnaissance Orbiter missionfor NASA's Science Mission Directorate.

For more information on CRISM and the Mars Reconnaissance Orbiter, including instrument images, visit: http://crism.jhuapl.edu