LOS ANGELES -- NASA scientists have discovered new evidence that briny, liquid water is flowing on Mars during its warmest months, raising the chances life could exist on the red planet, the space agency said yesterday.
NASA first found signs of water on Mars more than a decade ago, but earlier indications were that any existing water would be frozen and concentrated at the poles.
Recently analyzed images from NASA's Mars Reconnaissance Orbiter satellite show dark, finger-like features that extend down some slopes and crater walls on the planet during its late spring through summer, fading in the Martian winter.
"This is the best evidence we have to date of a liquid water occurring today on Mars," said Philip Christensen, a geophysicist at Arizona State University, Tempe, in a NASA panel announcing the findings in Washington.
NASA scientists believe that if there is liquid water on Mars, it would be highly salty and lie beneath the surface. That would explain why it would not freeze in the planet's frigid surface temperatures, which can fall to about 200 degrees below zero Fahrenheit, or evaporate in its low air pressure.
"It is more like a syrup, maybe, in how it flows," said Alfred McEwen of the University of Arizona, Tucson, principal investigator in charge of a camera on the Mars orbiter called a High Resolution Imaging Science Experiment. He is the lead author of a report on evidence of water flows published Thursday in the journal Science.
Any liquid water on Mars would likely lie beneath the planet's surface because its above-ground atmosphere is so minimal -- roughly 100 times thinner than on Earth -- that liquid water would quickly evaporate, scientists said.