BALTIMORE, Md., Aug. 16 -- With the recent launch of NASA's Mars Reconnaissance Orbiter spacecraft, the Compact Reconnaissance Imaging Spectrometer for Mars -- or CRISM -- joins the set of high-tech detectives seeking traces of water on the red planet. Built by the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., CRISM is the first visible-infrared spectrometer to fly on a NASA Mars mission. Its primary job is to 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. Peering through a telescope with a 4-in. 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. CRISM is mounted on a gimbal, allowing it to follow targets on the surface as the orbiter passes overhead. It will spend the first half of a two-year orbit mission mapping Mars at 650-ft. 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. 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 next March, use aerobraking to circularize its orbit, and to settle into its science orbit by November 2006. For more information, visit: crism.jhuapl.edu