If the Curiosity rover had been sent to Mars in ancient times, it might have found itself sinking in a stream.
The 2,000-pound
super-rover, which made its now-legendary landing on Mars on August 6,
has come across stones in conglomerate rock suggesting that water must
have flowed there in the past.
One such rock outcrop is
called Hottah, after Hottah Lake in Canada's Northwest Territories. It
looks like someone took a jackhammer and lifted up a sidewalk, said John
Grotzinger, lead scientist for the Curiosity mission, at a press
conference Thursday.
The consensus is that
"this is a rock that was formed in the presence of water," Grotzinger
said. "We can characterize that water as being a vigorous flow."
In and around this
bedrock, Curiosity has come across rounded gravels. The rocks appear to
have been subjected to a sediment transport process, carried by either
water or wind, said scientist Rebecca Williams of the Planetary Science
Institute in Tucson, Arizona.
The gravels seem too large to have been transported by wind, meaning it's likely that this is a stream bed.
A second rock outcrop,
called Link, holds similar evidence. Scientists used data from Curiosity
and the orbiters at Mars to enhance their understanding of the area.
The water flowing in
these rock formations was probably somewhere between ankle and hip deep,
said Curiosity science co-investigator William Dietrich of the
University of California, Berkeley.
Scientists believe the
water and sediment flowed down the crater into an alluvial fan -- a
geological formation created by material that water transports. At least
intermittently, this fan appears to have extended down to the area
where the rover landed.
It's hard to say how long ago this water flowed -- an estimate would be "thousands to millions of years," Dietrich said.
Previously, scientists
have used data from past Mars missions to speculate about channels on
the planet, and whether water could have flowed in them. This is the
first direct observation of streambed material, Dietrich said.
There are no plate
tectonics on Mars, meaning the planet does not have moving plates
underneath the surface that cause quakes. So why does this Hottah rock
formation look the way it does?
Grotzinger hypothesizes
that "Somewhere near this outcrop, a small impact occurred and lifted
the beds up and rotated them," he said.
The rover did not employ
any of its chemistry tools to examine the area; rather, scientists made
their judgments about the rocks based on photos.
Curiosity is now
three-quarters of the way between Hottah and Glenelg, its next official
stop. Glenelg was chosen as a target because it has three types of
terrain, including layered bedrock, making it a potentially interesting
place for Curiosity to try out its drill.
An unsolved mystery is
whether life could have been supported on Mars. Water is a necessary
ingredient, but an energy source and carbon are also essential.
Curiosity can detect
organic molecules and tear them apart to deliver details about them back
to Earth, but they would still not be definitive evidence that life
existed. Such molecules can come from nonliving sources, and Curiosity
doesn't have the technology to make that distinction. That will have to
wait for another mission.
This rover's ultimate
destination is Mount Sharp, a 3-mile-high mountain with layers of
sediment that will provide more opportunities to search for organic
molecules.
Curiosity recently
tested out its contact instruments on a rock called Jake Matijevic. It
used its Alpha Particle X-Ray Spectrometer (APXS) instrument to touch
the rock, and the Mars Hand Lens Imager (MAHLI) to take close-up photos.
Another instrument, ChemCam, shot laser pulses at the rock and finished
its testing on Monday.
The $2.6 billion mission is slated to last for two years, but previous rovers have far outlasted their estimated lifetimes.
The Spirit rover operated from 2004 to 2010, and the Opportunity rover has been chugging along since 2004. These twin rovers had initial mission periods of only 90 days
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