With the August 12 launch of
NASA’s Mars Reconnaissance
Orbiter spacecraft from Cape
Canaveral Air Force Station, Fla., the Compact
Reconnaissance Imaging Spectrometer
for Mars—or CRISM—joins the set of hightech
detectives seeking traces of water on
the red planet.
Built by Johns Hopkins’ Applied Physics
Laboratory, CRISM is the first visible-infrared
spectrometer to fly on a NASA Mars
mission. Its primary job: Look for the residue
of minerals that form in the presence of
water, the “fingerprints” left by evaporated
hot springs, thermal vents, lakes or ponds on
Mars when water could have existed on the
surface.
With unprecedented clarity, CRISM will
map areas on the martian surface down
to house-sized scales—as small as 60 feet
across—when the spacecraft is in its average
orbit altitude of about 190 miles.
“CRISM plays a very important role in
Mars exploration,” APL’s Scott Murchie,
the instrument’s principal investigator, said.
“Our data will identify sites most likely to
have contained water and which would
make the best potential landing sites for
future missions seeking fossils or even traces
of life on Mars.”
Though certain landforms provide evidence
that water may once have flowed on
Mars, Murchie said scientists have little
evidence of sites containing mineral deposits
created by long-term interaction between
water and rock. The NASA Rover Opportunity
found evidence for liquid water in
Meridian Planum, a large plain near Mars’
equator, but that is only one of many hundreds
of sites where future spacecraft could
land.
Peering through a telescope with a fourinch
aperture, and with a greater capability
to map spectral variations than any similar
instrument sent to another planet, CRISM
will read 544 “colors” in reflected sunlight
to detect minerals in the surface. Its highest
resolution is about 20 times sharper than
any previous look at Mars in infrared wavelengths.
“At infrared wavelengths, rocks that look
absolutely the same to human eyes become
very different,” Murchie said. “CRISM has
the capability to take images in which different
rocks will ‘light up’ in different colors.”
CRISM is mounted on a gimbal, allowing
it to follow targets on the surface as the
orbiter passes overhead. CRISM will spend
the first half of a two-year orbit mission
mapping Mars at 650-foot scales, searching
for potential study areas. Several thousand
promising sites will then be measured in
detail at CRISM’s highest spatial and spectral
resolution. CRISM will also monitor
seasonal variations in dust and ice particles
in the atmosphere, supplementing data
gathered by the orbiter’s other instruments
and providing new clues about the martian
climate.
“CRISM will improve significantly on
the mapping technology currently orbiting
Mars,” said Peter Bedini of APL, CRISM
project manager. “We’ll not only look for
future landing sites, but we’ll be able to provide
details on information the Mars Exploration
Rovers are gathering now. There is a
lot more to learn, and after CRISM and the
Mars Reconnaissance Orbiter, there will still
be more to learn. But with this mission we’re
taking a big step in exploring and understanding
Mars.”
As the Mars Reconnaissance Orbiter
cruises to its destination, the CRISM operations
team continues to fine-tune the software
and systems it will use to command the
instrument and receive, read, process and
store a wealth of data from orbit—more than
10 terabytes when processed back on Earth,
enough to fill more than 15,000 compact
discs. The spacecraft is set to reach Mars
in March, use aerobraking to circularize
its orbit and settle into its science orbit by
November 2006.
APL, which has built more than 150
spacecraft instruments over the past four
decades, led the effort to develop, integrate
and test CRISM. CRISM’s co-investigators
are top planetary scientists from Brown University,
the Jet Propulsion Laboratory, Northwestern
University, the Space Science Institute,
Washington University in St. Louis,
University of Paris, the Applied Coherent
Technology Corp. and NASA’s Goddard
Space Flight Center, Ames Research Center
and Johnson Space Center.
The Jet Propulsion Laboratory, a division
of the California Institute of Technology,
Pasadena, manages the Mars Reconnaissance
Orbiter mission for NASA’s Science
Mission Directorate.
For more information on CRISM and
the Mars Reconnaissance Orbiter, including
instrument images, go to crism.jhuapl.edu.