Slim Chance of water on Mars

High-resolution pictures and infrared spectra recorded by NASA's Mars Reconnaissance Orbiter (MRO) indicate that fresh, bright streaks on two steep gullies don't signify a recent flow of water, as scientists suggested just a year ago. The deposits on the steep gullies could just as easily have been formed by landslides of dry, sandy material, assert Alfred McEwen of the University of Arizona in Tucson. Other gullies, however, whose slopes are too shallow to permit landslides, do offer clear evidence of watery flows. These flows might have occurred several million years ago, when the Martian climate was warmer.

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