Hematite

http://marsrovers.jpl.nasa.gov/spotl...ematite01.html

Hematite
Jet Propulsion Laboratory
January 23, 2004

Busy as she has been with work, JPL's Dr. Joy Crisp, project
scientist for the Mars Exploration Rover Project, found time a
few weeks ago to do a little shopping. The new necklace she
bought is a simple string of dark grey beads and wasn't
expensive. What makes it significant is that it is made of
specular hematite, which for Mars scientists like Crisp may
prove to be more special than diamonds.

On Earth, the shiny grey mineral has been used to make
jewelry for hundreds of years. On Mars, grey hematite may
help prove whether large amounts of liquid water ever flowed
on Mars' surface. Where water was, life may have had a
chance to thrive as well.

Hematite is made up of iron and oxygen-a
type of iron oxide. It takes its name from the Greek word for
"blood," and is a rusty color in powdered form. Fine-grained
hematite helps gives Mars its characteristic red hue.

"Grey hematite is a mineral indicator of past water," says
Crisp. "It is not always associated with water, but it often is."
Deposits of grey hematite are typically found in places where
there has been standing water or mineral hot springs, such as
those in Yellowstone. The mineral can precipitate out of water
and collect in layers at the bottom of a lake, spring, or other
standing water. But hematite can also occur without water, as
the result of volcanic activity.

Scientists have wanted to find out which of these processes
created grey hematite on Mars since 1998, when Mars Global
Surveyor spotted large concentrations of the mineral near the
planet's equator. This discovery provided the first mineral
evidence that Mars' history may have included water.

If all goes well, they'll get a close look at Mars' grey hematite
when Opportunity, Spirit's rover twin, lands this week in an
area rich in the grey mineral. To find out what helped produce
the hematite - water or volcanic activity - they'll be
examining both the form of the hematite and the company it is
keeping.

"We want to know if the grains of hematite appear to be
rounded and cemented together by the action of liquid water or
if they're crystals that grew from a volcanic melt," says Crisp.
"Is the hematite in layers, which would suggest that it was
laid down by water, or in veins in the rock, which would be
more characteristic of water having flowed through the rocks."

"The area where we are going has 10 to 15 percent grey
hematite," Crisp says. "What are the other materials found
with the hematite? Clays and carbonates would indicate there
had been water in the area. If the area had been volcanic, you
would expect to see other types of minerals like olivine and
pyroxene."

"We're very interested to know if this region could have been
like Yellowstone, with hot springs, so we'll be looking to see
if there are other minerals in the area such as those at
Yellowstone."

"Knowing just how the hematite on Mars was formed will help
us characterize the past environment and determine whether
that environment was favorable for life," says Crisp. "One big
question, of course, is whether life ever started on Mars. This
mission probably won't tell us that, but it may well lead to
future mission that can answer that question."

In the meantime, Crisp wears her newly acquired hematite
necklace for luck.