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| [PHOTO: JD Hancock/CC BY 2.0] |
Washington: NASA's Mars Reconnaissance Orbiter (MRO) has provided images
allowing scientists for the first time to create a 3-D reconstruction of
ancient water channels below the Martian surface.
The spacecraft took
numerous images during the past few years that showed channels attributed to
catastrophic flooding in the last 500 million years. Mars during this period
had been considered cold and dry. These channels are essential to understanding
the extent to which recent hydrologic activity prevailed during such arid conditions.
They also help scientists determine whether the floods could have induced
episodes of climate change.
The estimated size of
the flooding appears to be comparable to the ancient mega flood that created
the Channeled Scablands in the Pacific Northwest region of the United States in
eastern Washington.
The findings are
reported in the March 7 issue of Science Express by a team of scientists from
NASA, the Smithsonian Institution, and the Southwest Research Institute in
Houston.
"Our findings
show the scale of erosion that created the channels previously was
underestimated and the channel depth was at least twice that of previous
approximations," said Gareth Morgan, a geologist at the National Air and
Space Museum's Center for Earth and Planetary Studies in Washington and lead
author on the paper. "This work demonstrates the importance of orbital
sounding radar in understanding how water has shaped the surface of Mars."
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| This illustration schematically shows where the Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter detected flood channels that had been buried by lava flows in the Elysium Planitia region of Mars. [IMAGE CREDIT: NASA/JPL-Caltech/Sapienza University of Rome/Smithsonian Institution/USGS] |
Marte Vallis'
morphology is similar to more ancient channel systems on Mars, especially those
of the Chryse basin. Many scientists think the Chryse channels likely were
formed by the catastrophic release of ground water, although others suggest
lava can produce many of the same features. In comparison, little is known
about Marte Vallis.
With the SHARAD
radar, the team was able to map the buried channels in three dimensions with
enough detail to see evidence suggesting two different phases of channel
formation. One phase etched a series of smaller branching, or
"anastomosing," channels that are now on a raised "bench"
next to the main channel. These smaller channels flowed around four streamlined
islands. A second phase carved the deep, wide channels.
"In this region,
the radar picked up multiple 'reflectors,' which are surfaces or boundaries
that reflect radio waves, so it was possible to see multiple layers, "
said Lynn Carter, the paper's co-author from NASA's Goddard Space Flight Center
in Greenbelt, Md. "We have rarely seen that in SHARAD data outside of the
polar ice regions of Mars."
The mapping also
provided sufficient information to establish the floods that carved the
channels originated from a now-buried portion of the Cerberus Fossae fracture
system. The water could have accumulated in an underground reservoir and been
released by tectonic or volcanic activity.
"While the radar
was probing thick layers of dry, solid rock, it provided us with unique
information about the recent history of water in a key region of Mars,"
said co-author Jeffrey Plaut of NASA's Jet Propulsion Laboratory (JPL),
Pasadena, Calif.