Thermal Imaging Gets under Mars' Skin

Scientists have released the most detailed results to date from the thermal emission imaging system, or Themis, on the Mars Odyssey spacecraft. Led by principal investigator Philip R. Christensen, a team at Arizona State University in Tempe has operational control of the system, including determination of the imaging strategy.

As reported in the June 27 issue of Science, the IR imager complements mineral mapping activities of the Mars Global Surveyor's thermal emission spectrometer. The Surveyor provided proof of rock units layered at a meter to tens-of-meters scale, and Themis enabled the scientists to determine that the physical and compositional properties of these layers vary.

For example, this false-color Themis image of part of the Ganges Chasma in Valles Marineris is superimposed on topographic data obtained by Mars Global Surveyor. The color differences show compositional variations of rocks exposed in the wall and floor of Ganges (blue and purple) and in dust and sand on the canyon rim (red and orange).

Designed and developed by researchers at the university in partnership with Raytheon/Hughes Santa Barbara Remote Sensing of Goleta, Calif., Themis includes a 10-band multispectral detector assembly with a range of 6.5 to 15 µm and a 100-m/pixel resolution, the highest resolution of any of the current IR imaging systems used in Mars exploration. The system also incorporates a five-band visual detector, developed under subcontract at Malin Space Science Systems in San Diego, that captures images at wavelengths of 450 to 850 nm with a resolution of 19 m per pixel.