[meteorite-list] 'Blueberries' Are The Answer To Key Mars Puzzle

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:51 2004
Message-ID: <200403171627.IAA08256_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99994790

'Blueberries' are answer to key Mars puzzle
David Chandler
New Scientist
March 17, 2004

The Mars rover Opportunity has now solved the key puzzle it was sent to the
Meridiani Planum to figure out: where is the hematite that was spotted in
the area by the Mars Global Surveyor orbiter? The answer is in the
"blueberries", the tiny mineral spheres that litter the rover's landing
site.

The question was a key one, because hematite almost always forms in water,
and water is thought to be a pre-requisite for life. Scientists led by
Arizona State University's Phil Christensen revealed their discovery at the
Lunar and Planetary Sciences Conference in Houston, Texas, on Tuesday.

Finding the hematite in the spheres makes sense, because earlier data from
the rover showed the spheres are almost certainly concretions formed when
water deposited layer after layer of minerals around a minute grain of sand.

Ever since it landed in January, Opportunity has been seeing more and more
of the spheres, covering the soil, embedded in the bedrock, and seemingly
strewn across the flat plateau surrounding the landing crater.

However, until now, nobody knew what they were made of. This was because at
a few millimetres across they are far too small to fill the field of view of
any of the rover's three spectrometers.

Berry bowl

The challenge was to find a place where the spheres were sufficiently
concentrated to provide a target for the spectrometers. A "berry bowl"
provided the solution, a shallow depression in the bedrock where dozens of
spheres had collected in a tight bunch.

All three rover instruments, the mini-TES, Mossbauer, and Alpha Proton X-ray
Spectrometers, as well as its microscope, were used on Saturday and Sunday
to gather data and provided the definitive evidence.

The surrounding bedrock showed no sign of hematite at all, while the
concentrated berries showed a very strong signal. It is now clear that,
while not pure hematite, the spheres contain the primary concentrations of
the mineral.

They can account for the hematite seen on the soil surface, because they are
strewn across it, and for its absence in the bounce marks made by the
rover's landing, because pictures show that all the spheres were driven into
the soil and out of sight by the force of impact.

Lost lakes?

There is one remaining question about the hematite, however. It appears to
be even more concentrated on the plains outside the crater. Does that mean
that there may be an additional source as well, perhaps an overlying layer
of rock, or just that the plain is strewn with many millions of spheres?

Opportunity is expected to drive out onto that plain in a week or two, and
should have a chance to answer that question as well.

Christensen, who designed the mini-TES, is hopeful that additional
hematite-rich formations may be found that might prove the presence not just
of water, but of large bodies of standing water that may have persisted for
long periods.
Received on Wed 17 Mar 2004 11:27:50 AM PST