Douglas Isbell
Headquarters, Washington, DC                     Aug. 25, 1999 
(Phone:  202/358-1547)  

Mary Hardin/Frank O'Donnell 
Jet Propulsion Laboratory, Pasadena, CA 
(Phone:  818/354-5011)  

RELEASE:  99-97 

MARS POLAR LANDER TO ARRIVE ON SMOOTH, LAYERED TERRAIN

       A strip of gentle, rolling plains near the Martian South 
Pole will serve as a welcome mat when NASA's Mars Polar Lander 
touches down on the Red Planet on Dec. 3.

       NASA unveiled the landing site, a swath of terrain 
measuring about 1,500 square miles (4,000 square kilometers), at a 
briefing today at NASA Headquarters, Washington, DC. 

       "We looked for a site with slopes no steeper than 10 
degrees," said Project Scientist Dr. Richard Zurek of NASA's Jet 
Propulsion Laboratory (JPL), Pasadena, CA.  "We chose a location 
with some surface features but no cliffs or jagged peaks, because 
the spacecraft will be able to land safely, yet we'll still 
accomplish our science goals."

       The landing site is located at 76 degrees South latitude 
and 195 degrees West longitude, near the northern edge of the 
South Pole's layered terrain.  

       "We believe this layered terrain is a record of climate 
changes on Mars, and in a sense, digging into its surface will be 
like reading tree rings or layers in an ice core," Zurek said.  
"The presence of fine layers of dust and ice with varying 
thickness will indicate changes in weather patterns and layer 
formation that have been repeated in recent history.  In addition, 
we may find evidence of soil particles that formed in ancient seas 
on Mars and were later blown into the polar regions."

     The landing will be targeted to the center of the site, a 
rectangular area 124 miles (200 kilometers) long and 12.4 miles 
(20 kilometers) wide.  The site was selected after the project 
team studied pictures and altimeter information gathered by NASA's 
Mars Global Surveyor, which is currently orbiting the planet.  The 
search was narrowed to four sites before the final location was 
chosen.  A backup landing site is located nearby, at 75 degrees 
South latitude and 180 degrees West longitude.  

       "For the next several weeks, we'll study newly transmitted 
Mars Global Surveyor images," said Flight Team Manager Dr. Sam 
Thurman at JPL.  "If necessary, we can retarget for the backup 
landing site as late as early October, when the flight team begins 
preparations for landing."

       The Dec. 3 landing occurs toward the end of spring in the 
Martian Southern Hemisphere.  The sun will shine all day, moving 
higher and lower in the sky but never dipping below the horizon.  
This nonstop sunshine will power the lander's solar panels for 90 
days, until the Martian seasons change and the lander's mission 
ends.

       Launched on Jan. 3, 1999, Mars Polar Lander will study the 
soil and look for ice beneath the surface of the Martian South 
Pole.  The lander also carries two Deep Space Two Microprobes that 
will be deployed about five minutes before the spacecraft enters 
the Martian atmosphere.  When they land, they'll penetrate beneath 
the soil surface to look for water ice at nearby locations.  The 
microprobes were developed under NASA's New Millennium Program.

       Images of the landing site and additional information about 
Mars Polar Lander are available at the following Web site:

         http://mars.jpl.nasa.gov/msp98/lander/

       Additional information about Deep Space Two is available at 
the following Web site:

              http://nmp.jpl.nasa.gov/ds2/

       JPL manages Mars Polar Lander and the New Millennium 
Program for NASA's Office of Space Science, Washington, DC.  JPL 
is a division of the California Institute of Technology, Pasadena, 
CA.