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ZL2VAL > ROVERS 03.03.04 09:24l 129 Lines 5808 Bytes #999 (0) @ WW
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Subj: Strong evidence of watery past
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Sent: 040302/1955Z @:ZL2AB.#46.NZL.OC #:36983 [New Plymouth] FBB7.00g
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Press Releases
NEWS RELEASE: 2004-074
March 02, 2004
Opportunity Rover Finds Strong Evidence Meridiani Planum Was Wet
Scientists have concluded the part of Mars that NASA's Opportunity rover
is exploring was soaking wet in the past.
Evidence the rover found in a rock outcrop led scientists to the
conclusion. Clues from the rocks' composition, such as the presence of
sulfates, and the rocks' physical appearance, such as niches where
crystals grew, helped make the case for a watery history.
"Liquid water once flowed through these rocks. It changed their texture,
and it changed their chemistry," said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y., principal investigator for the science
instruments on Opportunity and its twin, Spirit. "We've been able to
read the tell-tale clues the water left behind, giving us confidence in
that conclusion."
Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA
Headquarters, Washington, said, "NASA launched the Mars Exploration
Rover mission specifically to check whether at least one part of Mars
ever had a persistently wet environment that could possibly have been
hospitable to life. Today we have strong evidence for an exciting
answer: Yes."
Opportunity has more work ahead. It will try to determine whether,
besides being exposed to water after they formed, the rocks may have
originally been laid down by minerals precipitating out of solution at
the bottom of a salty lake or sea.
The first views Opportunity sent of its landing site in Mars' Meridiani
Planum region five weeks ago delighted researchers at NASA's Jet
Propulsion Laboratory, Pasadena, Calif., because of the good fortune to
have the spacecraft arrive next to an exposed slice of bedrock on the
inner slope of a small crater.
The robotic field geologist has spent most of the past three weeks
surveying the whole outcrop, and then turning back for close-up
inspection of selected portions. The rover found a very high
concentration of sulfur in the outcrop with its alpha particle X-ray
spectrometer, which identifies chemical elements in a sample.
"The chemical form of this sulfur appears to be in magnesium, iron or
other sulfate salts," said Dr. Benton Clark of Lockheed Martin Space
Systems, Denver. "Elements that can form chloride or even bromide salts
have also been detected."
At the same location, the rover's Mössbauer spectrometer, which
identifies iron-bearing minerals, detected a hydrated iron sulfate
mineral called jarosite. Germany provided both the alpha particle X-ray
spectrometer and the Mössbauer spectrometer. Opportunity's miniature
thermal emission spectrometer has also provided evidence for sulfates.
On Earth, rocks with as much salt as this Mars rock either have formed
in water or, after formation, have been highly altered by long exposures
to water. Jarosite may point to the rock's wet history having been in an
acidic lake or an acidic hot springs environment.
The water evidence from the rocks' physical appearance comes in at least
three categories, said Dr. John Grotzinger, sedimentary geologist from
the Massachusetts Institute of Technology, Cambridge: indentations
called "vugs," spherules and crossbedding.
Pictures from the rover's panoramic camera and microscopic imager reveal
the target rock, dubbed "El Capitan," is thoroughly pocked with
indentations about a centimeter (0.4 inch) long and one-fourth or less
that wide, with apparently random orientations. This distinctive texture
is familiar to geologists as the sites where crystals of salt minerals
form within rocks that sit in briny water. When the crystals later
disappear, either by erosion or by dissolving in less-salty water, the
voids left behind are called vugs, and in this case they conform to the
geometry of possible former evaporite minerals.
Round particles the size of BBs are embedded in the outcrop. From shape
alone, these spherules might be formed from volcanic eruptions, from
lofting of molten droplets by a meteor impact, or from accumulation of
minerals coming out of solution inside a porous, water-soaked rock.
Opportunity's observations that the spherules are not concentrated at
particular layers in the outcrop weigh against a volcanic or impact
origin, but do not completely rule out those origins.
Layers in the rock that lie at an angle to the main layers, a pattern
called crossbedding, can result from the action of wind or water.
Preliminary views by Opportunity hint the crossbedding bears hallmarks
of water action, such as the small scale of the crossbedding and
possible concave patterns formed by sinuous crestlines of underwater
ridges.
The images obtained to date are not adequate for a definitive answer. So
scientists plan to maneuver Opportunity closer to the features for a
better look. "We have tantalizing clues, and we're planning to evaluate
this possibility in the near future," Grotzinger said.
JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Office of Space
Science, Washington.
For information about NASA and the Mars mission on the Internet, visit
http://www.nasa.gov .
Images and additional information about the project are also available
at http://marsrovers.jpl.nasa.gov
and http://athena.cornell.edu
=========================
73 de Alan, (Sysop ZL2AB).
AX25:ZL2VAL@ZL2AB.#46.NZL.OC
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Message timed: 08:47 on 2004-Mar-03 (NZT)
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Points to ponder
~~~~~~~~~~~~~~~~
Marriage
~~~~~~~~
Getting married is very much like going to a restaurant with friends.
You order what you want, then when you see what the other person has,
you wish you had ordered that instead.
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