- Massive erosion shaped the surface of Mars, according
to planetary scientists at Washington University in St. Louis.
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- Brian M. Hynek, doctoral candidate in Earth and Planetary
Sciences, and Roger J. Phillips, Ph.D., professor of earth and planetary
sciences and director of Washington University,s McDonnell Center for the
Space Sciences, suggest that western Arabia Terra, an area the size of
the European continent, experienced an extensive erosion event caused by
flowing water.
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- "We argue that this entire region has been massively
eroded," said Hynek. "The region used to look like the rest of
the highlands, but a vertical kilometer of material - enough to fill the
Gulf of Mexico - has been relocated downslope and spread out into the northern
plains."
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- The researchers used high-resolution topographic data
from the Mars Orbiter Laser Altimeter (MOLA) instrument on the Mars Global
Surveyor mission to construct detailed maps of the planet's surface. "Before
this mission, topography was known only within a kilometer at best; now
we are accurate to within half a meter at any given point on the surface
of Mars," said Hynek. MOLA's accuracy, and the more than half a billion
data points it has collected, reveals many previously unknown features
of Mars' surface. The research was published in the May issue of the journal
Geology.
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- Mars is divided into two main areas: the older Southern
Highlands with lots of craters and valley networks, and the younger Northern
Lowlands with few craters and no valley networks.
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- When the researchers began studying maps from the new
data, they noticed that one region, western Arabia Terra, is a kilometer
lower than the rest of the highlands and borders the lowlands to the north.
Before the Mars Global Surveyor mission, this region was lumped in with
the rest of the highlands. But the new topography reveals that there is
much more going on here than previously thought. Looking carefully at western
Arabia, they noticed that it differs from the rest of the highlands in
having very few large craters, and only a few traces of valley networks,
and numerous erosional remnants.
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- "This combination makes it very likely that the
entire region was swept away," said Hynek. But how can you remove
all this material and carry it away?
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- "Lots of things can erode planets. Wind is very
effective on long timescales; volcanoes, ice and glaciers can all erode
features, but on this large of a scale these are unlikely explanations,"
said Hynek. He said that the massive size of the eroded area and the remnants
of valley networks suggest running water was responsible.
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- The researchers believe the erosion event took place
very early in Mars' history, during the Late Noachian, and ended by around
3.8 to 3.5 billion years ago. The timing coincides with other water features
found on the planet and heavy outflow of lava from volcanoes early in Mars'
history, as the researchers noted in the journal Science earlier this year.
Volcanic eruptions emit great amounts of water, carbon dioxide, sulfur
and other greenhouse gases as well as lava and ash. This could have led
to the development of an atmosphere on Mars that persisted for a few hundred
million years - long enough to raise surface temperature above freezing
and maintain liquid water on the planet's surface.
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- "Mars has not always been cold and dry with little
happening on the surface. At one time it had a heyday," said Hynek.
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- The researchers are now focusing attention on a large
outcrop of hematite occurring within western Arabia Terra, the Terra Meridiani
region. Hematite, an iron oxide, forms in the presence of water on Earth.
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- "This is very likely to be one of two Mars Rover
landing sites in 2004," said Hynek. "We want to go where the
water was."
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- Note: This story has been adapted from a news release
issued by Washington University In St. Louis for journalists and other
members of the public. If you wish to quote from any part of this story,
please credit Washington University In St. Louis as the original source.
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