Feb. 15 (Bloomberg) -- New, detailed photographs of Mars show evidence of subterranean streams of liquid, including water, that once flowed long enough that they could have sustained simple forms of life, researchers say.

Photos from the U.S. National Aeronautics and Space Administration's Mars Reconnaissance Orbiter reveal a landscape of hills and sand dunes punctuated by rock bleached by minerals in ancient underground streams.

Those streams of water, or water mixed with liquid carbon dioxide, flowed for weeks or longer -- long enough to have supported bacteria or other simple life forms, according to a study by the American Association for the Advancement of Science, appearing in tomorrow's issue of the journal Science.

``The most interesting aspect we found in these new photos is that we can see that the water, with most likely other dissolved chemicals in it, resided in these areas for weeks or months or longer,'' said study co-author Chris Okubo, of the University of Arizona's Lunar and Planetary Laboratory.

``It means these areas would have been potentially habitable,'' he said in an interview.

Mars is the only planet in the solar system besides Earth where scientists believe life might have existed. While previous photos of the planet showed dry river channels and lakebeds, there has been no proof as to whether those surface areas were wet long enough to have supported life, Okubo said.

Orbiter's Mars camera photographed canyons in a Martian valley, the Valles Marineris, that is as wide as the U.S. and as much as seven times deeper than the Grand Canyon in places. The camera, which can pick out detail within a foot, showed rock formations with fractures and with bleached areas that on Earth are ``a clear indication'' that chemicals in liquids have circulated within the fractures, the study said.

Erosion over as much as millions of years exposed the areas to the surface and to Orbiter's camera.

To contact the reporter on this story: Barbara Powell in Dallas at Bpowell4@bloomberg.net.

Last Updated: February 15, 2007 14:41 EST