[meteorite-list] Destination: Meridiani Planum

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:05 2004
Message-ID: <200401221718.JAA17450_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/headlines/y2004/22jan_meridianiplanum.htm

Destination: Meridiani Planum
NASA Science News
January 22, 2004

On January 24, 2004, NASA's Mars rover Opportunity is scheduled to land
on a Martian plain in search of evidence for water.

January 22, 2004: On January 24, at about 9:05 p.m. Pacific Standard Time,
NASA's second rover is scheduled to arrive on Mars. Opportunity will land
near the equator, on a plain known as Meridiani Planum. It'll be halfway
around the planet from Gusev Crater, where its twin, Spirit, is already
feeding eager scientists as much data as it can transmit.

Meridiani Planum interests scientists because it contains an
ancient layer of hematite, an iron oxide that, on Earth, almost
always forms in an environment containing liquid water. The
site appears dry now. So how did the hematite get there?
Was there once water in the area? If so, where did it go?

"There are five or six hypotheses to explain the hematite on
Mars, but none of them are a slam-dunk," says NASA's
Mars Landing Site Science Coordinator John Grant. "We have
to go there to find out which is correct."

It's possible, for example, that the hematite was produced directly
from iron-rich lavas, a process that would not require liquid water. But
if water was involved--and that's considered most probable--then,
most likely, the hematite either formed from the iron-rich waters of
an ancient lake, or it formed when Martian groundwater percolated
though layers of volcanic ash.

Opportunity's suite of spectrometers, cameras, microscopes, and sampling
tools should allow scientists to figure out where the hematite came from.
For instance, if a mineral called goethite is found among the hematite,
that would mean that the hematite formed in watery conditions. On the
other hand, if magnetite is found and goethite is not, a watery past is
unlikely.

Just being able to look at the way the hematite is distributed will
provide some answers. If the hematite occurs as a thin layer within a
pile of layers, then it's likely to have formed in a long-ago lake, says
Grant. If, on the other hand, it occurs in more discrete veins, deposited
between cracks in rocks, "then it's much more likely to have been
associated with groundwater."

If you look in the Earth, he says, in places where the groundwater
percolates through the subsurface, "you see evidence for life all over
the place." This mission, Grant emphasizes, is not seeking evidence of
Martian life. It's looking for environments that were favorable for life,
and in which evidence of life may have been preserved.

Knowing how the hematite formed will help determine if Meridiani Planum
is that kind of environment.

Meridiani Planum is unique on Mars because there's so much exposed hematite
there, according to data gathered by NASA's Mars Global Surveyor spacecraft.
"Localized deposits also exist in two other sites: the deep canyon Valles
Marinaris and a place called called Aram Chaos," notes Grant, "but neither
are accessible based on the current landing system." Meridiani Planum has
more hematite and it's a safer place to land.

Meridiani Planum is also attractive because the site appears to be eroding,
with once-buried craters that are now half-revealed. Opportunity might be
able to inspect layers of ground that would otherwise be hidden, affording
a glimpse into the area's distant past.

"There's so much we don't know about Mars," says Grant. "But I really think
we're going to come out of this mission with a better understanding of what
Mars has been like over time, and where we might go for our next step."

Visit http://marsrovers.jpl.nasa.gov for the latest information about Spirit
and Opportunity.
Received on Thu 22 Jan 2004 12:18:46 PM PST


Help support this free mailing list:



StumbleUpon
del.icio.us
reddit
Yahoo MyWeb