Evidence Of An Ancient Stream Found On Mars By Curiosity Rover
Lee Rannals for redOrbit.com – Your Universe Online
It has been almost two months since NASA’s Curiosity rover landed on Mars and it has already found evidence of an ancient stream on the Red Planet.
Curiosity ran up upon a series of stones cemented into a layer of conglomerate rock and shot back some images of the Martian features back to NASA.
NASA said the sizes and shapes of those stones offer clues to the speed and distance of an ancient stream’s flow.
“From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep,” said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. “This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it.”
Curiosity found the ancient stream between the north rim of Gale Crater and the base of Mount Sharp, which is a mountain inside the crater.
Earlier imaging of the region from Mars orbit shows an alluvial fan of material washed down from the rim, streaked by many channels, sitting uphill of the new finds.
The shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel known as Peace Vallis feeds into the alluvial fan.
NASA said the abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time.
This discovery comes from examining two outcrops known as “Hottah” and “Link.”
“Hottah looks like someone jack-hammered up a slab of city sidewalk, but it’s really a tilted block of an ancient streambed,” said Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena.
The gravels in conglomerates at both outcrops range in size from a grain of sand to a golf ball, and some are angular, while others are rounded.
“The shapes tell you they were transported and the sizes tell you they couldn’t be transported by wind. They were transported by water flow,” according to Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute in Tucson, Arizona.
NASA said the team may use Curiosity to learn about the composition of the material, which holds the conglomerate together and could reveal more characteristics of the wet environment that formed these deposits.
The stones in the conglomerate provide a sampling from above the crater rim, so the team may examine several of them to learn about a variety of regional geology.
Curiosity still has its sights set on the slope of Mount Sharp in Gale Crater, where clay and sulfate minerals have been detected.
“A long-flowing stream can be a habitable environment,” Grotzinger said. “It is not our top choice as an environment for preservation of organics, though. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment.”
One image released by NASA compares the Link outcrop of rocks on Mars with similar rocks seen on Earth. The two areas look nearly identical in the picture.
During Curiosity’s two-year prime mission, it will use its 10 instruments to investigate whether areas of Gale Crater have ever offered environmental conditions favorable for microbial life.
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2012-09-27 13:21:15
Source: http://www.redorbit.com/news/space/1112702348/mars-curiosity-stream-evidence-092712/
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If this is an ancient stream bed, then why are the river pebbles on top and clean from dust?