Don Savage

Headquarters, Washington DC

(Phone: 202-358-1727)

Cynthia M. O’Carroll

Goddard Space Flight Center, Greenbelt, Md.

(Phone: 301-614-5563)

RELEASE: 00-36

Some of Mars’ best kept secrets, long buried beneath
the surface of the red planet, were recently revealed by
instruments on NASA’s Mars Global Surveyor spacecraft.

New observations of Mars reveal that the planet’s flat
northern lowlands were an early zone of high heat flow that
later may have been the site of rapid water accumulation,
according to a view of the Martian interior generated using
data from Mars Global Surveyor (MGS). Elevation and
gravity measurements, which have been used to probe beneath
the surface of Mars, indicate a period of rapid cooling
early in Martian history, and evidence for large, buried
channels that could have formed from the flow of enormous
volumes of water.

This global view of the Martian interior was generated
from gravity measurements with the Radio Science experiment
and elevation measurements from the Mars Orbiter Laser
Altimeter (MOLA) instruments. Gravity and topography
measurements were combined to reveal the structure of the
crust on Mars, which preserves the record of melting of the
interior and the heat loss from the planet over time.

“The crustal thickness map shows that, as for Earth,
Mars has two distinct crustal provinces,” explained Dr.
Maria Zuber of the Massachusetts Institute of Technology,
Cambridge, MA, and lead author of a study to be published
in the March 10 issue of Science. Beneath the rough
southern highlands and Tharsis volcanic province the crust,
estimated at 50 miles thick, thins progressively from the
South pole toward the North. In contrast, the northern
lowlands and Arabia Terra region of the southern highlands
have a crust of uniform thickness, about 22 miles deep.

The crustal structure accounts for the elevation of
the Martian northern lowlands, which controlled the
northward flow of water early in Martian history, producing
a network of valleys and outflow channels. The new gravity-
field data suggest that the transport of water continued
far into the northern plains. The gravity shows features
interpreted as channels buried beneath the northern
lowlands emanating from Valles Marineris and the Chryse
and Kasei Valles outflow regions.

The features are about 125 miles wide and over a
thousand miles long, with characteristics that can be
explained by water flow on the surface or in a submarine
environment, later buried by sediments. The large size of
these channels implies that any bodies of water in the
northern lowlands could have accumulated rapidly. The now-
buried channels may represent the means for filling an
early ocean.

The gravity and topography also provide information on
the cooling of Mars over time, which bears on the early
climate and history of water. “The observations suggest
that the northern lowlands was a location of high heat loss
from the interior early in Martian history, probably due to
a period of vigorous convection and possibly plate
recycling inside of Mars,” said Dr. Sean Solomon, Director
of the Department of Terrestrial Magnetism of the Carnegie
Institution in Washington, DC, and a co-author of the

The high heat-loss zone corresponds to the part of
Mars proposed to have been the site of an ancient ocean.
The rapid transport of heat to the surface in this region
would have released onto the surface and into the
atmosphere gases and water or ice trapped in the interior.
The time of rapid interior heat loss may correspond to the
period when Mars had a warmer climate, liquid water flowed
on the surface, and the planet’s surface was shielded from
the solar wind by a global magnetic field.

During the ongoing Mars Global Surveyor mapping
mission the Radio Science and MOLA experiments will
continue to collect data on a near-continuous basis through
the end of the mission in February 2001. The MOLA
instrument was designed and built by the Laser Remote
Sensing Branch of the Laboratory for Terrestrial Physics at
NASA’s Goddard Space Flight Center, Greenbelt, MD. The
Radio Science experiment is implemented from the Center for
Radio Astronomy of Stanford University, Palo Alto, CA. The
Mars Global Surveyor mission is managed for NASA’s Office
of Space Science, Washington, DC, by the Jet Propulsion
Laboratory, Pasadena, CA, a division of the California
Institute of Technology.



Maps of the interior of Mars may be viewed at:

Information about the MGS Radio Science investigation can
be found at:

Information about the MOLA investigation can be found at:

The MGS home page is:

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