PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

Contact: Franklin O'Donnell

FOR IMMEDIATE RELEASE                         September 8, 1994

     NASA has selected an ancient flood plain on Mars as the 
landing site for the 1996 mission of Mars Pathfinder, one of the 
first in a new generation of small, low-cost spacecraft.

     Eons ago, when water flowed on Mars, great floods inundated 
the landing site, located on a rocky plain in an area known today 
as Ares Vallis.  The site is 850 kilometers (527 miles) southeast 
of the location of Viking Lander 1, which in 1976 became the 
first spacecraft to land on Mars.  Pathfinder will be the first 
to land on Mars since the twin Viking landers arrived almost 20 
years ago.

     The spacecraft, scheduled to arrive at Mars on July 4, 1997, 
will parachute down to Ares Vallis at the mouth of an ancient 
outflow channel chosen for the variety of rock and soil samples 
it may present.

     The purpose of the new Pathfinder mission is to demonstrate 
an inexpensive system for cruise, entry, descent and landing on 
Mars, said Project Manager Anthony Spear and Project Scientist 
Dr. Matthew Golombek of NASA's Jet Propulsion Laboratory.

     The lander, carrying the microrover, will aerobrake in the 
upper Martian atmosphere using an aeroshell and a parachute.  
Just before impact, airbags will inflate to cushion the landing. 
The microrover will then roll out to examine the rocks and soil 
nearby.

     Both lander and rover will carry scientific instruments and 
cameras.  The lander will make atmospheric and meteorological 
observations during descent and function as a weather station on 
the surface, as well as a radio relay station for the rover.

     The constraints on the location have to do with engineering 
considerations, Spear said. Since the spacecraft are solar-
powered, the best site is one with maximum sunshine and in July, 
1997, the sun will be directly over the 15 degrees north latitude 
region of the planet.

     The elevation must be as low as possible, Spear added, so 
the descent parachute has sufficient time to open and slow the 
lander to the correct terminal velocity.  The landing will be 
within a 100- by 200-kilometer (60- by 120-mile) ellipse around 
the targeted site due to uncertainties in navigation and 
atmospheric entry.

     Ares Vallis, which meets the engineering constraints, was 
chosen after a workshop earlier this year that involved the 
invited participation of the entire scientific community 
concerned with Mars.  More than 60 scientists from the United 
States and Europe attended.

     The Ares Vallis site is also a "grab bag" location, 
according to Golombek, set at the mouth of a large outflow 
channel in which a wide variety of rocks are potentially within 
the reach of the rover. Even though the exact origins of the 
samples would not be known, he said, the chance of sampling a 
variety of rocks in a small area could reveal a lot about Mars.

     The rocks would have been washed down from highlands at a 
time when floods moved over the surface of Mars.  Several 
potential sites were listed where ancient flood channels emptied 
into Chryse Planitia, having cut through crustal units and ridged 
plains where the water would have picked up material and 
deposited it on the plain.

     Other sites that were considered included Oxia Palus, a dark 
highlands region that contains highland crust and dark wind-blown 
deposits; Maja Valles Fan, a delta fan which drained an outflow 
channel; and the Maja Highlands, just south of  Maja Valles.  All 
of the sites were studied using Viking orbiter data.

     Both the Pathfinder lander and rover have stereo imaging 
systems. The rover, additionally, carries an alpha proton x-ray 
spectrometer with which it will examine the composition of the 
rocks.  The imaging system will reveal the mineralogy of surface 
materials as well as the geologic processes and surface-
atmosphere interactions that created and modified the surface.  
The instrument package will also enable scientists to determine 
dust particle size and water vapor abundance in the atmosphere.

     JPL manages the Mars Pathfinder mission for NASA's Office of 
Space Science, Washington, D.C.

                             #####

9/2/94 JJD
#9453