Shifting dark streaks on the surface of Mars are signs that water is flowing there today, scientists said on Thursday.
The possible presence of liquid water is certain to revive speculation
that Mars is teeming with microbial organisms. The recipe for life, at
least as we know it, calls for liquid water, carbon-based molecules and a
source for energy.
There is plenty of ice on Mars, but the chemical reactions for life come to a halt when water freezes.
High-resolution photographs taken by NASA's Mars Reconnaissance Orbiter,
which arrived at Mars in 2006, show finger-like streaks up to five
yards wide that appear on some steep slopes in the late Martian spring.
These streaks grow and shift through summer, reaching hundreds of yards
in length before they fade in winter. One crater had about 1,000
streaks.
“We have this circumstantial evidence for water flowing on Mars,” said
Alfred S. McEwen of the University of Arizona, who is the principal
investigator for the camera, during a news conference on Thursday. “We
have no direct detection of water.” Mr. McEwen and his colleagues report
their findings in an article published in Friday's issue of the journal
Science. The scientists said the best explanation they could offer for
the streaks was that they were caused by a flow of extremely salty water
down the slopes.
