[meteorite-list] Evidence For Extensive, Olivine-Rich Bedrock On Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon May 30 21:50:02 2005
Message-ID: <200505310149.j4V1nOc12462_at_zagami.jpl.nasa.gov>

http://www.marsdaily.com/news/mars-odyssey-05a.html

Evidence For Extensive, Olivine-Rich Bedrock On Mars
MarsDaily
May 30, 2005

Honolulu HI (SPX) -
By using new, high spatial resolution infrared data from NASA's Mars
Odyssey spacecraft, Victoria Hamilton from the University of Hawaii at
Manoa and Philip Christensen from Arizona State University have
concluded that a region on the surface of Mars known to contain
olivine-rich rocks is actually 4 times larger than previously estimated.

The bedrock in question is adjacent to Syrtis Major, one of Mars'
largest volcanoes. This region is of interest to scientists because it
lies in a relatively old region on Mars, and yet contains significant
amounts of olivine, a mineral that can weather rapidly in the presence
of water.

These results are reported in the June 2005 cover story of the journal
Geology.

Based on its infrared spectral signatures, this region was previously
identified by the NASA Mars Global Surveyor Thermal Emission
Spectrometer (MGS TES) (launched in 1996) as having an enrichment in the
mineral olivine (the dominant mineral component of several Martian
meteorites) relative to typical Martian basalts.

Infrared spectra of rocks are like fingerprints, allowing scientists to
determine their mineral make-up.

Using higher spatial resolution data available from the Mars Odyssey
spacecraft's Thermal Emission Imaging System (THEMIS) (launched in
2001), the researchers were able to expand the boundaries of the
high-olivine region by comparing the infrared spectra and temperature
measurements acquired by THEMIS to geological features in visible
wavelength digital images taken by THEMIS and the MGS Mars Orbiter Camera.

"By having the different types of high resolution visible, spectral, and
temperature information available, we were able to see both geochemical
and geological features on Mars that showed us that this high-olivine
region is much larger than we thought previously," said Hamilton, an
assistant professor in the Hawaii Institute of Geophysics and Planetology.

"We now have a better view of the detailed geology of this ancient region."

The region is northeast of the Syrtis Major volcanic shield, and was
previously shown to have an area of ~ 30,000 km2.

In this new study, the deposits in question are now shown to be 113,000
km2, almost 4 times larger than previously thought.

As a comparison, the Big Island of Hawai'i, with its five volcanoes, has
a surface area of ~10,500 km2 - almost 11x smaller than the deposits on
Mars. These olivine-rich basalts appear to be present in the form of
in-place, layered rock units that are being exposed by tectonic uplift
and the erosion of younger rocks.

One of the findings of the study is that at least some of these rocks
were erupted onto the surface of Mars, where they might have been
exposed to more water and weathering than if they had been intruded into
the subsurface, as previously proposed.

"How much liquid water was present on the surface of Mars in the past,
and for how long, are big questions in planetary science right now,"
Hamilton says.

"Under many conditions, olivine turns into other minerals very rapidly
in the presence of water, so the preservation of all this olivine in a
very old region of Mars is intriguing. One hypothesis is that this area
of Mars has not seen much water.

"Now that we know the detailed distribution of these olivine-rich rocks,
we can search more of the spectral data for minerals that might have
formed if the olivine was exposed to water at some point in its past."

This research is covered in the June issue of the GEOLOGY, published by
the Geological Society of America, and is featured on the magazine's cover.

Research article citation: Evidence for extensive, olivine-rich bedrock
on Mars, Victoria E. Hamilton and Philip R. Christensen, Geology, Volume
33, Number 6, June 2005. Http://www.gsajournals.org

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http://starbulletin.com/2005/05/28/news/story7.html

UH study deepens Mars water mystery
By Helen Altonn
Honoluly Star Bulletin
May 28, 2005

A region on Mars' surface with the mineral olivine is four times larger
than estimated, again raising the question of whether water existed on
the red planet, Hawaii and Arizona planetary geologists say.

Scientists are eager to find out if water was on Mars because it is
considered a key element for life, and large quantities of olivine
indicate the lack of water.

The findings of professors Victoria Hamilton of the University of Hawaii
Institute of Geophysics and Planetology and Philip Christensen of
Arizona State University are reported in the June issue of the journal
Geology.

Olivine is the most susceptible mineral to weathering by water, yet the
large quantities seen on Mars are in an ancient area 3 billion to 4
billion years old, Hamilton said yesterday.

This suggests the rocks might have been protected from any water on the
surface of Mars or possibly were never exposed to any, she said.

She said olivine rapidly turns into other minerals in the presence of
water under many conditions, "so the preservation of all this olivine in
a very old region of Mars is intriguing."

At least some of the rocks were erupted on Mars' surface where they
might have been exposed to more water and weathering than if they had
been forced into the subsurface as previously proposed, the researchers
found.

Hamilton and Christensen are studying high-resolution infrared data from
the space agency's Mars Odyssey and Mars Global Surveyor spacecraft.
They have NASA research funding.

Christensen is responsible for a two-camera thermal imaging system
called THEMIS on Odyssey that identifies the mineral content of rocks
and other surface materials.

He also has a thermal emission spectrometer in orbit around Mars on the
Global Surveyor. It produced the first global mineral map of Mars with
measurements of the infrared signatures of minerals on the surface.

The imaging spectrometer on Odyssey will identify where wet environments
once existed on Mars -- places where there could be past or present
signs of life.

Hamilton and Christensen are trying to understand what the rocks are on
Mars and what they say about the planet's geologic history. She said
they are trying to figure out where meteorites on Earth came from Mars,
which would reveal a lot about the planet.

About a year or two ago, the researchers identified places on Mars with
infrared spectra like meteorites found on Earth, Hamilton said. With
higher-resolution data available, they are getting more details about
Mars' geology, she said.

In the past, places nearby were covered with dust, which they cannot see
through, she said.

"We can't see through dust with the spectrometer, but we can get more
spatial information about the temperature of rocks and, basically, using
the temperature data, are able to figure out that olivine-rich rock
continues under the dust to cover a bigger area than we realized before."

Now that they know the detailed distribution of the olivine-rich rocks,
Hamilton said, "We've really got to look in detail and find any minerals
that suggest this olivine has weathered and what was the chemistry
involved."
Received on Mon 30 May 2005 09:49:23 PM PDT