PUBLIC INFORMATION 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
Contact: Diane Ainsworth
FOR IMMEDIATE RELEASE
October 9, 1997
PATHFINDER TEAM PAINTS AN EARTH-LIKE PICTURE OF EARLY MARS
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' past.
"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 core.
"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."
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 http://www.jpl.nasa.gov/marsnews or on the Mars
Pathfinder project's home page at http://marsweb.jpl.nasa.gov .
Images from Mars Pathfinder and other planetary missions are
available at NASA's Planetary Photojournal web site at
http://photojournal.jpl.nasa.gov.
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.
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