One picture, taken through filters at nine infrared wavelengths, inaugurated the assaying of Martian surface minerals by the Thermal Emission Imaging System. THEMIS will map the entire planet at 100-meter resolution, 30 times more sharply than ever before, with a particular emphasis on minerals that can form only in the presence of water. Other infrared pictures shown on Friday, taken both in daylight and in the dark of night, sharply distinguish rocky from sandy terrain.
THEMIS is also taking pictures in visible light. These resolve features as small as 18 meters across, which is not as detailed as the ultrasharp images still being amassed by the orbiting Mars Global Surveyor. But the latter cover only a small fraction of the Martian surface, whereas Mars Odyssey's will eventually cover the entire planet.
Mars Odyssey carries two other primary instruments. The Gamma Ray Spectrometer (GRS) will map about 20 chemical elements to depths of a few feet underground, though with only 250-kilometer resolution. Scientists are especially eager to turn up areas with buried hydrogen, a sign of water ice that could be mined by future astronauts. And the news is already very positive: water appears to permeate a large area of the planet's southern hemisphere. Investigator William Boynton (University of Arizona) reports that a strong hydrogen signal was immediately found within 30° of the south pole, an area roughly the size of Europe.
Last is the Mars Radiation Environment Experiment (MARIE), intended to study radiation that could endanger humans on Mars and in interplanetary space. MARIE went silent last August, but ground controllers still hope to fix it.
Mars Odyssey will also act as a communications link for future missions, including NASA's Exploration Rovers to be launched in 2003.
Planetary scientists have good reason to be elated with the craft's early success. Of NASA's five previous Mars missions in the last 20 years, three failed completely or crashed on arrival.