From: LARRY KLAES (ljk4_at_msn.com)
Date: Thu Mar 06 2003 - 23:28:03 PST
----- Original Message -----
From: NASA Jet Propulsion Laboratory
Sent: Friday, March 07, 2003 1:50 AM
To: ljk4_at_msn.com
Subject: Scientists Say Mars Has a Liquid Iron Core
MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov http://www.jpl.nasa.gov/
Donald Savage (202) 358-1547
NASA Headquarters, Washington, D.C.
Mary Hardin (818) 354-0344
Jet Propulsion Laboratory, Pasadena, Calif.
News Release: 2003-032
March 6, 2003
Scientists Say Mars Has a Liquid Iron Core
New information about what is inside Mars shows the red planet has a
molten liquid iron core, confirming the interior of the planet has
some similarity to Earth and Venus.
Researchers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
analyzing three years of radio tracking data from the Mars Global
Surveyor spacecraft, concluded that Mars has not cooled to a
completely solid iron core, rather its interior is made up of either a
completely liquid iron core or a liquid outer core with a solid inner
core. Their results are published in the March 7, 2003 online issue of
the journal Science.
"Earth has an outer liquid iron core and solid inner core. This may be
the case for Mars as well," said Dr. Charles Yoder, a planetary
scientist at JPL and lead author on the paper. "Mars is influenced by
the gravitational pull of the Sun. This causes a solid body tide with
a bulge toward and away from the Sun (similar in concept to the tides
on Earth). However, for Mars this bulge is much smaller, less than 1
centimeter (0.4 inch). By measuring this bulge in the Mars gravity
field we can determine how flexible Mars is. The size of the measured
tide is large enough to indicate the core of Mars can not be solid
iron but must be at least partially liquid."
The team used Doppler tracking of a radio signal emitted by the Global
Surveyor spacecraft to determine the precise orbit of the spacecraft
around Mars. "The tidal bulge is a very small but detectable force on
the spacecraft. It causes a drift in the tilt of the spacecraft's
orbit around Mars of one-thousandth of a degree over a month," said
Dr. Alex Konopliv, a planetary scientist at JPL and co-author on the
paper.
The researchers combined information from Mars Pathfinder on the Mars
precession with the Global Surveyor tidal detection to draw
conclusions about the Mars core, according to Dr. Bill Folkner of JPL,
another co-author of the paper.
The precession is the slow motion of the spin pole of Mars as it moves
along a cone in space (similar to a spinning top). For Mars, it takes
170,000 years to complete one revolution. The precession rate
indicates how much the mass of Mars is concentrated toward the center.
A faster precession rate indicates a larger dense core, compared to a
slower precession rate.
In addition to detection of a liquid core for Mars, the results
indicate the size of the core is about one-half the size of the
planet, as is the case for Earth and Venus, and that the core has a
significant fraction of a lighter element such as sulfur.
In addition to measuring the Mars tide, Global Surveyor has been able
to estimate the amount of ice sublimated, changed directly into a
gaseous state, from one pole into the atmosphere and then accreted
onto the opposite pole. "Our results indicate the mass change for the
southern carbon dioxide ice cap is 30 to 40 percent larger than the
northern ice cap, which agrees well with the predictions of the global
atmosphere models of Mars," said Yoder.
The amount of total mass change depends on assumptions about the shape
of the sublimated portion of the cap. The largest mass exchange occurs
if we assume the cap change is uniform or flat over the entire cap,
while the lowest mass exchange corresponds to a conically shaped cap
change.
JPL manages the Mars Exploration Program for NASA's Office of Space
Science, Washington, D.C. JPL is a division of the California
Institute of Technology in Pasadena.
This archive was generated by hypermail 2.1.6 : Thu Mar 06 2003 - 23:42:49 PST