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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. [Image credit: NASA/JPL-Caltech/Univ. of Arizona] |
Pasadena, California: A NASA spacecraft is providing new evidence of a wet
underground environment on Mars that adds to an increasingly complex picture of
the Red Planet's early evolution.
The new information
comes from researchers analyzing spectrometer data from NASA's Mars
Reconnaissance Orbiter (MRO), which looked down on the floor of McLaughlin
Crater. The Martian crater is 57 miles (92 kilometers) in diameter and 1.4
miles (2.2 kilometers) deep. McLaughlin's depth apparently once allowed
underground water, which otherwise would have stayed hidden, to flow into the
crater's interior.
Layered, flat rocks
at the bottom of the crater contain carbonate and clay minerals that form in
the presence of water. McLaughlin lacks large inflow channels, and small
channels originating within the crater wall end near a level that could have
marked the surface of a lake.
Together, these new
observations suggest the formation of the carbonates and clay in a
groundwater-fed lake within the closed basin of the crater. Some researchers
propose the crater interior catching the water and the underground zone
contributing the water could have been wet environments and potential habitats.
The findings are published in Sunday's online edition of Nature Geoscience.
"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," said Joseph Michalski, lead author of the paper, which has five
co-authors. Michalski also is affiliated with the Planetary Science Institute
in Tucson, Ariz., and London's Natural History Museum.
Michalski and his
co-authors used the Compact Reconnaissance Imaging Spectrometer for Mars
(CRISM) on MRO to check for minerals such as carbonates, which are best
preserved under non-acidic conditions.
"The MRO team
has made a concerted effort to get highly processed data products out to
members of the science community like Dr. Michalski for analysis," said
CRISM Principal Investigator Scott Murchie of the Johns Hopkins University
Applied Physics Laboratory in Laurel, Md. "New results like this show why
that effort is so important."
Launched in 2005, MRO
and its six instruments have provided more high-resolution data about the Red
Planet than all other Mars orbiters combined. Data is made available for
scientists worldwide to research, analyze and report their findings.
"A number of
studies using CRISM data have shown rocks exhumed from the subsurface by meteor
impact were altered early in Martian history, most likely by hydrothermal
fluids," Michalski said. "These fluids trapped in the subsurface
could have periodically breached the surface in deep basins such as McLaughlin
Crater, possibly carrying clues to subsurface habitability."
McLaughlin Crater
sits at the low end of a regional slope several hundreds of miles long on the
western side of the Arabia Terra region of Mars. As on Earth, groundwater-fed
lakes are expected to occur at low regional elevations. Therefore, this site
would be a good candidate for such a process.
"This new report
and others are continuing to reveal a more complex Mars than previously
appreciated, with at least some areas more likely to reveal signs of ancient
life than others," said MRO project scientist Rich Zurek of NASA's Jet
Propulsion Laboratory (JPL) in Pasadena, California.