Workhorse Mars Imager Marks 10 Years

NASA’s Mars Odyssey has now been orbiting the Red Planet for 10 years. Its main camera — the multiband THEMIS, or thermal emission imaging system — began scientific operation on Feb. 19, 2002. It has circled the planet nearly 45,000 times and has taken more than half a million images at infrared and visible wavelengths.

“THEMIS has proven itself a workhorse,” said Philip Christensen, the camera’s designer and principal investigator as well as a professor at Arizona State University’s College of Liberal Arts and Sciences. “It’s especially gratifying to me to see the range of discoveries that have been made using this instrument.”

Taken on Feb. 19, 2002, this was the first scientific image of Mars taken by THEMIS. It shows an area in Acheron Fossae, north of the giant volcano Olympus Mons, where mesas and valleys lie bounded by geologic faults. The image shows an area 11 x 6 mi; the smallest details visible in the original image are 59 ft wide. (Images: NASA/JPL-Caltech/Cornell/Arizona State University)

Some of the scientific results documented by THEMIS over the past 10 years include:

    • confirming that hematite is widespread on Meridiani Planum, which led NASA to send one of its Mars Exploration Rovers there

    • discovering CO₂ gas jets at the south polar ice cap in spring

    • discovering chloride salt deposits across the planet

    • making the best global image map of Mars ever done

    • identifying safe landing sites for NASA’s Mars Phoenix spacecraft by finding the locations with the fewest hazardous boulders

    • monitoring dust activity in the Martian atmosphere

    • discovering that a large impact crater, Aram Chaos, once contained a lake

    • discovering that Mars has more water-carved channels than previously thought

    • discovering dacite, a more evolved form of volcanic lava not previously known on the Red Planet

Taken on THEMIS’ 10th anniversary, this image shows a region on Mars in Nepenthes Mensae, part of Terra Cimmeria. The view depicts a knobby landscape where the southern highlands are breaking up as the terrain descends into the northern lowlands. The image covers 11 x 32 mi; the smallest details visible in the original image are 59 ft wide.

THEMIS combines a five-wavelength visual imaging system with a nine-wavelength infrared imaging system. By comparing daytime and nighttime infrared images of any given area, scientists can determine many of the physical properties of the rocks and soils on the ground.

Mars Odyssey has a two-hour orbit that is nearly “sun-synchronous,” meaning that Odyssey passes over the same part of Mars at roughly the same local time each day. In September 2008, its orbit was shifted toward an earlier time of day, which enhanced THEMIS’ mineralogical detection capability.

“Both Odyssey and THEMIS are in excellent health, and we look forward to years more science with them,” Christensen said.

For more information, visit: www.asu.edu