[meteorite-list] Hidden Face of Mars Uncovered by Father & Daughter

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:07:04 2004
Message-ID: <200210251630.JAA12959_at_zagami.jpl.nasa.gov>

Geological Society of America
Denver, Colorado

Contact: Ann Cairns
Phone: 303-357-1056; Fax: 303-357-1074
acairns_at_geosociety.org

FOR IMMEDIATE RELEASE: October 25, 2002

GSA Release No. 02-53

Hidden Face of Mars Uncovered by Father & Daughter

Ghosts of the most ancient craters in the solar system are
materializing on Mars. Using altimeter data from the Mars
Global Surveyor and special graphics software, a father
and daughter have found the circular outlines of the Red
Planet's earliest impact craters and basins -- pounded
into what remains of the planet's first crust.

Planetary geologist Herb Frey of NASA's Goddard Space
Flight Center and his daughter Erin Frey, a junior at
South River High School, in Edgewater, Md., will be
explaining their discoveries in two consecutive
presentations at the annual meeting of the Geological
Society of America on Sunday, October 27, in Denver, CO.

In both studies Mar Orbiting Laser Altimeter data was
loaded into a graphics program that allowed colors to be
assigned to different elevations. By manually shifting
and stretching the colors to study various ranges of
elevation change, they were able to detect very subtle
quasi-circular depressions, or "QCDs" for short. The
Freys contend that these are craters from early times
before the Noachian (pronounced "no-ACK-ee-en") -- the
name for the oldest identified geological time period
on Mars.

What it all means, says Erin Frey, is that the oldest
visible Martian crust is not really the oldest. "We are
talking about crust that's actually older," she said.
Something from a period they are calling the "Pre-Noachian."

Erin Frey focused her search for Pre-Noachian craters on a
relatively small area near the Hellas Basin of Mars that
has been previously considered Early in age. What she
found were subtle signs that there was a yet earlier
episode of intense impacts, largely covered over by
subsequent cratering and billions of years of geological
processes.

Herb Frey took a similar approach in studying the entire
planet for signs of very early large impacts. In the flat
northern lowlands of Mars, for instance, he found QCDs
buried by eons of accumulated dust, volcanic materials,
and other sediments. Placing the cratered surfaces in
order, Herb Frey says that it appears the buried lowlands
are older than the visible cratered surface of the
Noachian southern highlands, and that the QCDs his
daughter found in the highlands are older still.

How old? "We can't assign absolute ages because we don't
know how far back these subsurfaces go," says Erin Frey.
What's more, despite previous geologists assigning ages
of about four-billion-years old to the Noachian and the
Southern Highlands, it's just a guess based on the order
in which things appeared to have occurred on Mars and
what's known about similarly cratered crust on the Moon.

"It's actually a very squirrelly business," said Herb Frey
of attempts to assign actual ages to Martian features
without actual rock samples isotopically. Still, there are
some things the older crust can tell us about the history
of Mars.

For one thing, says Herb Frey, the evidence of earlier
impact periods means that some process that fit in to a
relatively short interval formed the oddly low northern
hemisphere of Mars. That means hypotheses of plate
tectonics and large-scale motion in Mars' mantle may be
less likely -- since they tend to be very slow processes.
Alternatively, what becomes more likely is that the
northern lowlands were formed by a massive impact event.
"It fits in with the timescale," he said.

Until samples from the cratered terrains can be studied in
labs, there are experiments that can be sent to Mars that
will help clear things up, says Herb Frey. One would be a
series of seismic sensors that could listen to Mars quakes
and use the information to discern the interior structure
of the planet -- as is done on Earth. European and US
scientists are already planning such a project, says Frey.

CONTACT INFORMATION

During the GSA Annual Meeting, Oct. 27-30, contact Christa
Stratton at the GSA Newsroom in the Colorado Convention
Center, Denver, Colorado, for assistance and to arrange
for interviews: (303) 228-8565.

The abstracts for these presentations are available at:
   http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_41753.htm
   http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_44774.htm

Post-meeting contact information:

Erin Frey
South River High School
Edgewater, MD 21037
dancer7068_at_aol.com

Herbert V. Frey
Geodynamics Branch
NASA Goddard Space Flight Center
Greenbelt, MD 20771
frey_at_core2.gsfc.nasa.gov

Ann Cairns
Director of Communications
Geological Society of America
acairns_at_geosociety.org
303-357-1056
Received on Fri 25 Oct 2002 12:30:21 PM PDT