February 16, 2007
*
Stunning color pictures from Mars offer new evidence that plentiful
groundwater once percolated through Martian bedrock.
The new images, taken by NASA's Mars Reconnaissance Orbiter, reveal a
terrain of banded rocks similar to that found in the southwestern U.S.,
said Chris Okubo, a postdoctoral researcher at the University of
Arizona's Lunar and Planetary Laboratory.
The new pictures show that Martian rocks in this sandy landscape are riddled with small cracks.
These cracks bear telltale signs that fluid—probably water—seeped through them hundreds of millions of years ago.
Prominent riblike structures along the cracks, for instance, suggest
that running water dissolved minerals in the Martian soil, forming a
kind of cement.
The water also dissolved dark minerals out of the rocks, leaving light-colored "halos" around the cracks.
These findings are exciting, because they suggest that similar
water-filled fractures might still exist beneath the Martian surface,
scientists said.
"What we see at the surface today are glimpses of what used to be underground," Okubo said.
Okubo presented the new images at a press conference today in
San Francisco, California. His team's findings will appear in
tomorrow's issue of the journal Science.
Search for Life May Shift
Water is a key component of life as we know it, so the new discovery
will be useful in helping scientists hone the search for possible life
on Mars, researchers at the conference said.
There is already abundant evidence that early Mars was once
water rich, said Stephen Clifford, a Mars hydrologist from the Lunar
and Planetary Institute in Houston, Texas.
But the water has since retreated, presumably underground, and appears to have occasionally reached the surface in large floods.
Now that it is widely agreed that water once flowed along extensive
networks of cracks, a new clue falls into place in a lingering mystery.
"One of the problems [was] how, if the water is underground, you get so much of it to the surface at once," Clifford said.
Other Ingredients of Life
Water appears to have been very common at various times on Mars's
surface. So in the search for life it's now time to do more than seek
out places where the red planet was once wet, said Tori Hoehler, an
astrobiologist with NASA's Ames Research Center in Moffett Field,
California.
Instead, scientists need to start thinking about other possible requirements for life, such as energy, Hoehler said.
For example, he said, microorganisms might be able to harness
chemical energy from Martian rocks, as some earthly bacteria appear to
do.
"This is the next thing we should be looking for on Mars," he said.
But expanding the search for life requires studying the geology in more detail, the scientists said.
NASA's Opportunity rover is currently on the rim of Victoria Crater, where scientists have observed outcrops of rock similar to that seen in Okubo's photos. (Related photos: Mars rovers).
"If we can get to [those outcrops]," Hoehler said, "it would be a great to visit them."
But, Okubo added, "right now, they're on the far side of the craters, so it may take a while for Opportunity to get there."
National Geographic
*
(Read related story: "Mars's Water Could Be Below Surface, Experts Say" [January 25, 2007].)
See also:
|
