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The newspaper of The Johns Hopkins University October 23, 2006 | Vol. 36 No. 8
APL-built Mars Instrument Reveals New Details of Planet

NASA's newest Mars spacecraft — carrying the APL-built Compact Reconnaissance Imaging Spectrometer for Mars — is already revealing new clues about both recent and ancient environments on the red planet.

Scientists hope the Mars Reconnaissance Orbiter will answer questions about the history and distribution of Mars' water by combining data from the spacecraft's high-resolution camera, imaging spectrometer, context camera, ground-penetrating radar, atmospheric sounder, global color camera, radio and accelerometers.

Between Sept. 29 and Oct. 6, the first week of observations from low orbit, the instruments provided a good test of their capabilities by viewing dozens of sites that reflect different episodes in Mars' history. The orbiter will begin its primary science mission phase in early November, when Mars re-emerges from passing nearly behind the sun.

The instruments are seeing details in the shapes and icy composition of geologically young layering near the Martian north pole. Other views offer details of a midaltitude valley whose upper layers have been eroded away, revealing an underlying clay layer that formed a few billion years ago, when wet conditions produced the clay. Observations of a southern-hemisphere crater show fine-scale details of more recent gullies, adding evidence that they were carved by flowing water.

In Chasma Boreale, a vast valley that juts into the north polar ice cap, the spectrometer sees layers that vary in soil composition and in how much ice is mixed with the soil. A dark underlying layer contains little ice, but just beneath it lies ice-rich material resembling higher layers. The APL spectrometer, called CRISM for short, takes pictures both in visible light and infrared wavelengths useful for identifying what a target is made of.

"You see more-ice-rich and less-ice-rich layers, which tells you that conditions changed from the time one layer was deposited to the time another layer was deposited," said APL's Scott Murchie, CRISM principal investigator. "These layers are geologically young — on the order of thousands or millions of years — and may hold clues about climate cycles."

CRISM also examined a lower-latitude target named Mawrth Vallis. A previous spacecraft discovered ancient deposits of clay minerals that could form only if water was present for a long time at Mawrth Vallis. CRISM now has resolved smaller-scale compositional features and detected differing clay mineral content. The clay-rich areas show some of the best evidence for conditions possibly favorable for life on ancient Mars, Murchie said.

The mission's High Resolution Imaging Science Experiment camera, which, during testing week, imaged 64 areas including Victoria Crater, has shown unprecedented detail. "These images are truly beautiful, and since they resolve features the size of people, you can visualize yourself hiking around in these diverse terrains," said the camera's principal investigator, Alfred McEwen of the University of Arizona, Tucson.

Another observation of an unnamed southern crater shows relatively young gullies that look like those seen in many Mars locations viewed by NASA's Mars Global Surveyor orbiter. In the new observations, braided channels characteristic of sediment-rich streams are visible. This reinforces the interpretation that these geologically young gullies formed at least in part from erosion by flowing water.

The Mars Reconnaissance Orbiter is managed by the Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington.

For more on the orbiter, go to

For more on CRISM, go to


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