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This view of layered rocks on the floor of McLaughlin Crater
shows sedimentary rocks that contain spectroscopic evidence for
minerals formed through interaction with water. The High Resolution
Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance
Orbiter recorded the image. Image released Jan. 20, 2013.
CREDIT: NASA/JPL-Caltech/Univ. of Arizona
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New photos of a huge crater on Mars suggest water may lurk in crevices
under the planet's surface, hinting that life might have once lived
there, and raising the possibility that it may live there still,
researchers say.
Future research looking into the chances of
life on Mars could shed light on the origins of life on Earth, scientists added.
The discovery came from a study of images by NASA's powerful Mars
Reconnaissance Orbiter that revealed new evidence of a wet underground
environment on the Red Planet. The images focused on the giant
McLaughlin Crater, which is about 57 miles (92 kilometers) wide and so
deep that underground water appears to have flowed into the crater at
some point in the distant past.
Today, the crater is bone-dry but harbors clay minerals and other
evidence that liquid water filled the area in the ancient past.
"Taken together, the observations in McLaughlin Crater provide the best
evidence for carbonate forming within a lake environment instead of
being washed into a crater from outside," study lead author Joseph
Michalski, of the Planetary Science Institute in Tucson, Ariz., and
London's Natural History Museum, said in a statement. [
Search for Water on Mars (Photos)]
An annotated look at the huge McLaughlin Crater on
Mars, showing locations of minerals and clays created by water in the
ancient past. The region may have once been a groundwater lake billions
of years ago. Image released Jan. 20, 2013.
CREDIT: NASA/JPL-Caltech/Univ. of Arizona
A wet Mars underground
Space agencies have deployed many
missions to Mars
over the decades to explore how habitable its surface may have been or
is today. However, the Martian surface has been extremely cold, arid and
chemically hostile to life as we know it for most of the history of
Mars.
Instead of scanning the surface of Mars for life, scientists have
suggested the most viable habitat for ancient simple life may have been
in
Martian water hidden underground.
On Earth, microbes up to 3 miles (5 km) or more underground make up
perhaps half of all of the planet's living matter. Most of these
organisms represent some of the most primitive kinds of microbes known,
hinting that life may actually have started underground, or at least
survived there during a series of devastating cosmic impacts known as
the Late Heavy Bombardment that Earth and the rest of the inner solar
system endured about 4.1 billion to 3.8 billion years ago.
Since
Mars has less gravity
— a surface gravity of a little more than one-third Earth's — its crust
is less dense and more porous than that of our planet, which means that
more water can leak underground, researchers said. Wherever there is
liquid water on Earth, there is virtually always life, and microbes
underground on Mars could be sustained by energy sources and chemical
reactions similar to those that support deep-dwelling organisms on
Earth.
"The deep crust has always been the most habitable place on Mars, and
would be a wise place to search for evidence for organic processes in
the future," Michalski told SPACE.com. [
Search for Life on Mars: A Timeline (Gallery)]
Subterranean Mars
While researchers currently have no way to drill deep underground on
the Red Planet, they can nevertheless spot hints of what subterranean
Mars is like by analyzing deep rocks exhumed by erosion, asteroid
impacts or materials generated by underground fluids that have welled up
to the surface.
Such upwelling would first occur in deep basins like McLaughlin Crater —
as the lowest points on the surface, they would be where underground
water reserves would most likely get exposed.
Scientists focused on McLaughlin Crater because it is one of the
deepest craters on Mars. McLaughlin is about 1.3 miles (2.2 km) deep and
is located in Mars' northern hemisphere.
Do you think life exists on Mars?
The mineral composition of the floor of McLaughlin Crater suggests there
was a lake made of upwelled groundwater there. Channels seen on the
crater's eastern wall about 1,650 feet (500 meters) above its floor also
hint at the former presence of a lake surface.
Michalski was actually originally trying to disprove the idea that groundwater breached the surface in many locations on Mars.
"Lo and behold, there was strong evidence for that process in this
crater," he said. "Science is special because we are allowed to change
our minds."
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An ancient groundwater lake
The researchers estimate that a lake existed at McLaughlin Crater for
an unknown duration between 3.7 billion and 4 billion years ago. "That
makes the deposits as old as or older than the oldest rocks known to
exist on Earth," Michalski said.
Mounds seen on the crater floor may have come from landslides or
subsequent meteor impacts. These are important because they may have
rapidly buried crater floor sediments.
"That is really cool because rapid burial is the scenario that is most
advantageous for preservation of organic material, if any was present at
that time," Michalski said.
This color image draped onto digital topography
shows McLaughlin Crater in a 3D perspective, looking toward the east.
Light-toned deposits on the crater floor contain alteration minerals
that are overlayed by debris flows from Keren Crater, present on the
south rim. McLaughin Crater once contained a lake that was likely fed by
groundwater.
CREDIT: High Resolution Stereo Camera (HRSC)/Mars Express/Freie Universität Berlin
Since life on Earth may have begun underground, learning more about any
underground life that might have lived — or may still live — on Mars
could shed light on the
origins of life on Earth, researchers said.
"We should give serious consideration to exploring rocks representing
subsurface environments in future missions," Michalski said. "That
doesn't mean drilling, but instead exploring rocks formed from upwelling
groundwater, or rocks naturally exhumed from the subsurface by meteor
impact."
Michalski noted that some people may ask, "'Why do I hear about the
detection of water or possibility of life on Mars all the time?' The
answer is because
Mars
is habitable in more ways than we ever realized for many years, and we
are finding water in many forms and environments on Mars — many more
than we predicted for a long time."
The ingredients for life the researchers describe, "including energy
sources, would have been more available early in Mars' history, but it
doesn't take too much imagination to picture a scenario in which the
subsurface is habitable today," Michalski said. He cautioned, however,
"that is much different from saying that life is there today."
The scientists detailed their findings online Jan. 20 in the journal Nature Geoscience.
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