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Mars Pathfinder Team Paints An Earth-Like Picture Of Early Mars

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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