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Source : http://www.thejakartapost.com/news/2012/09/28/mars-rover-curiosity-finds-signs-ancient-

stream.html

Mars Rover Curiosity Finds Signs of Ancient Stream

Writtened by :

Alicia Chang, The Associated Press, Los Angeles | Sci-Tech

Fri, September 28 2012, 10:56 AM

The NASA rover Curiosity has beamed back pictures of bedrock that suggest a fast-moving stream, possibly waist-deep, once flowed on Mars a find that the mission's chief

scientist called exciting. There have been previous signs that water existed on the red planet

long ago, but the images released Thursday showing pebbles rounded off, likely by water,

offered the most convincing evidence so far of an ancient streambed.

There was "a vigorous flow on the surface of Mars," said chief scientist John

Grotzinger of the California Institute of Technology. "We're really excited about this."

The discovery did not come as a complete surprise. NASA decided to plunk Curiosity

down inside Gale Crater near the Martian equator because photos from space hinted that

the spot possessed a watery past. The six-wheeled rover safely landed Aug. 5 after a nail-biting plunge through the Martian atmosphere. It's on a two-year, $2.5 billion mission to

study whether the Martian environment could have been favorable for microbial life.

Present day Mars is a frozen desert with no hint of water on its radiation-scarred

surface, but geological studies of rocks by previous missions suggest the planet was warmer

and wetter once upon a time.

The latest evidence came from photos that Curiosity took revealing rounded pebbles

and gravel a sign that the rocks were transported long distances by water and smoothed

out.

The size of the rocks

ranging from a sand grain to a golf ball

indicates that they

could not have been carried by wind, said mission scientist Rebecca Williams of the

Planetary Science Institute in Tucson, Arizona.

Though Curiosity did not use its high-tech instruments to drill into the rocks or

analyze their chemical makeup, Grotzinger said scientists were sure that water played a role

based on just studying the pictures.

It's unclear how long the water persisted on the surface, but it easily could have

lasted "thousands to millions of years," said mission scientist Bill Dietrich of the University of

California, Berkeley.

Curiosity chanced upon the dried-up streambed while driving to Glenelg, an

intriguing spot where three types of terrain meet. Its ultimate destination is Mount Sharp, a

mountain rising from the center of crater floor, but it was not expected to travel there until

the end of the year.

Finding past water is a first step toward learning whether the environment could

have supported microbes. Scientists generally agree that besides water and an energy

source such as the sun, organic carbon is a necessary prerequisite for life.

While an ancient streambed holds promise as a potentially habitable environment,

scientists don't think it's a good place to preserve the carbon building blocks of life. That's

why the rover will continue its trek to the foothills of Mount Sharp where there's a better

chance of finding organics.