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.
"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."
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.
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.