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Mars Pathfinder
Welcome to Mars

PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

Contact: Diane Ainsworth

FOR IMMEDIATE RELEASE                 October 9, 1997


Mars is appearing more and more like a planet that was very
Earth-like in its infancy, with weathering processes and flowing water that
created a variety of rock types and a warmer atmosphere that generated
clouds, winds and seasonal cycles.

Those observations, along with new images taken by the Mars
Pathfinder rover and lander, and an update on the condition of the
spacecraft, were presented at an Oct. 8 press briefing originating from
NASA's Jet Propulsion Laboratory.

"What the data are telling us is that the planet appears to have
water-worn rock conglomerates, sand and surface features that were created
by liquid water," said Dr. Matthew Golombek, Mars Pathfinder project
scientist at JPL. "If, with more study, these rocks turn out to be made of
composite materials, that would have required liquid water flowing on the
surface to round the edges in pebbles we see on the surface or explain how
they were embedded in larger rocks. That would be a very important finding."

Golombek also stressed the amount of differentiation -- or
heating, cooling and recycling of crustal materials -- that appears to have
taken place on Mars. "We're seeing a much greater degree of differentiation
-- the process by which heavier elements sink to the center of the planet
while lighter elements rise to the surface -- than we previously thought,
and very clear evidence that liquid water was stable at one time in Mars'

"Water, of course, is the very ingredient that is necessary to
support life," he added, "and that leads to the $64,000 question: Are we
alone in the universe? Did life ever develop on Mars? If so, what happened
to it and, if not, why not?"

Despite recent communications problems with Earth, the Mars
Pathfinder lander and rover are continuing to operate during the Martian
days, when they can receive enough energy to power up spacecraft systems via
their solar panels. The mission is now into Sol 94, or the 94th Martian day
of operations, since landing on July 4.

"Everything that we have seen over the last 10 days (with respect
to communications) is like a twisty little maze with passages all alike,"
said Jennifer Harris, acting mission manager. "I am happy to report that we
have made contact with the spacecraft using its main transmitter. We were
able to confirm that we could send a command to the spacecraft to turn its
transmitter on and then turn it off.

"We don't know yet whether we are receiving that signal over the
low-gain or high-gain antenna," she added, "but we should be able to
determine this over the next few days."

The Mars Pathfinder team began having communications problems
with the spacecraft on Saturday, Sept. 27. After three days of attempting to
reestablish contact, they were able to lock on to a beacon signal from the
spacecraft's auxiliary transmitter on Oct. 1, which meant that the
spacecraft was still operational.

At that time they surmised that the communications problems were
most likely related to depletion of the spacecraft's battery and
uncertainties in the onboard clock. The last successful data transmission
cycle from Pathfinder was completed at 3:23 a.m. Pacific Daylight Time on
Sept. 27, which was Sol 83 of the mission.

Since then, efforts have been made during each Martian day to
reestablish contact with both the primary and auxiliary transmitter and
obtain engineering telemetry that would tell the team more about the health
of the lander and rover. On Oct. 7, the team was able to lock on to
Pathfinder's signal, via NASA's Deep Space Network 34-meter-diameter
(112-foot) dish antenna in Madrid, Spain, for about 15 minutes, using the
main transmitter. However, in repeating the process on Oct. 8, they did not
receive a signal.

The rover, which receives its instructions from Earth via the
lander, is currently running a contingency software program that was
preprogrammed to start up if the vehicle did not hear from the lander after
five Martian days. That program was powered on Oct. 6, on Sol 92 of the
mission. In this contingency mode, the rover is instructed to return to the
lander and begin circling it. This precaution is designed to keep Sojourner
close to the lander in the event that the spacecraft was able to begin
communicating with it again.

If normal communications are reestablished, the rover team will
send new commands to Sojourner to halt the contingency circling and begin a
traverse to a specific location.

Dr. William Folkner, an interdisciplinary scientist at JPL,
presented data on the rotation and orbital dynamics of Mars, which are being
obtained from two-way ranging and Doppler tracking of the lander as Mars
rotates. Measurements of the rate of change in Mars' spin axis have
important implications for learning more about the density and mass of the
planet's interior. Eventually, scientists may be able to determine whether
Mars' core is presently molten or fluid. The size of the core also can be
used to characterize the thickness, or radius, of Mars' mantle.

"By measuring the spin axis of Mars, we can learn something about
the interior of the planet, because the speed of the change in its
orientation is related to how the mass is distributed inside," Folkner said.
"If the core is fluid, its spin and the way in which the planet wobbles
slightly will be different from the spin and wobble of a planet with a solid

"If Mars' core is solid, then it can't be less than about 1,300
kilometers (807 miles) in radius, out of the planet's total radius of 3,400
kilometers (2,112 miles)," Folkner added. "If the core is made up of
something less dense than iron, if it's a mixture of, say, iron and sulfur,
then the core would be bigger, but it couldn't be bigger than about 2,000
kilometers (1,242 miles) in radius."

New close-up images of dunes around the landing site are showing
some scientists clear evidence that there is sand on the surface of Mars.
Identification of sand, as opposed to dust or pebbles, is a significant
factor in establishing that weathering processes such as erosion, winds and
flowing water all contributed to Mars' present landscape.

"We've made significant progress in establishing that water was a
dominant agent in forming the surface, and now we can say that there is
another agent at work, and that is the wind, that has created and modified
some of the landforms on a smaller and medium scale," said Dr. Wes Ward of
the U.S. Geological Survey, Flagstaff, AZ, a member of the Imager for Mars
Pathfinder team. "And because the water is no longer there, wind probably is
the dominant agent shaping the Martian surface at this moment."

Ward showed images of Ares Vallis, taken by the rover and Viking
1 orbiter images to point out the structural difference in these surface
features. While Viking 1 surface features around a rock nicknamed "Big Joe"
showed drifts, the dune-like surfaces in the Ares Vallis flood basin
resemble sand that has been blown southwest over the landing site. The
presence of sand also points to the likely presence of liquid water, needed
to create these small, 1-millimeter-diameter granules, and weathering agents
such as wind to blow them into small ridges and moats present around the
Ares Vallis rocks.

"The wind is quite an active agent," Ward said. "Sand is the
smoking gun, and as far as I'm concerned, the gun is smoking and has Colonel
Mustard's prints all over it. We are seeing sand at the landing site."

  [Image]  Dr. Greg Wilson, of Arizona State University, who is on the
Pathfinder atmospheric experiment team, reported increases in the pressure
of the Martian atmosphere and a drop in surface temperatures.

"We expect to see a continued increase in pressure and decrease
in temperatures as the dust season approaches and winds begin to lift more
dust into the Martian atmosphere," he said. "The dust season on Mars usually
begins in the next few weeks."

Additional information, images and rover movies from the Mars
Pathfinder mission are available on JPL's Mars news media web site at or on the Mars Pathfinder project's home
page at . Images from Mars Pathfinder and other
planetary missions are available at NASA's Planetary Photojournal web site

The Mars Pathfinder mission is managed by the Jet Propulsion
Laboratory for NASA's Office of Space Science, Washington, DC. The mission
is the second in the Discovery Program of fast-track, low-cost spacecraft
with highly focused science goals. JPL is a division of the California
Institute of Technology, Pasadena, CA.