NASA Mars Rover Opportunity Gets Green Light to Enter Endurance Crater

NASA has decided the potential science value gained by
sending Opportunity into a martian impact crater likely
outweighs the risk of the intrepid explorer not being able to
get back out.

Opportunity has been examining the rim of stadium-sized
“Endurance” crater since late May. The rover team used
observations of the depression to evaluate potential science
benefits of entering the crater and the traversability of its
inner slopes.

The soonest Opportunity could enter Endurance is early next
week. It will drive to the top of a prospective entry-and-
exit route on the southern edge of the crater and make a
final check of the slope. If the route is no steeper than
what recent testing runs at NASA’s Jet Propulsion Laboratory,
Pasadena, Calif., suggest a rover can climb, controllers plan
to radio Opportunity the command to go into the crater.

“This is a crucial and careful decision for the Mars
Exploration Rovers’ extended mission,” said Dr. Edward
Weiler, NASA’s Associate Administrator for Space Science.
“Layered rock exposures inside Endurance Crater may add
significantly to the story of a watery past environment that
Opportunity has already begun telling us. The analysis just
completed by the rover team shows likelihood that Opportunity
will be able to drive to a diagnostic rock exposure, examine
it, and then drive out of the crater. However, there’s no
guarantee of getting out again, so we also considered what
science opportunities outside the crater would be forfeited
if the rover spends its remaining operational life inside the
crater.”

At a rock outcrop in a small impact feature nicknamed, “Eagle
Crater,” where Opportunity first landed, the rover found
small-scale rock textures and evaporite mineral compositions
testifying that a body of salty water covered the site long
ago.

The wet environment may have been a suitable habitat for
life, if it ever existed on Mars. However, only the uppermost
layer of the region’s layered crust was exposed at Eagle
Crater, not deeper layers that could reveal what the
environment was like earlier.

The rock layer seen at Eagle Crater appears at Endurance
Crater, too. At Endurance, though, it lies above exposures of
thicker, older layers, which are the main scientific
temptation for sending Opportunity inside the crater.

“Answering the question of what came before the evaporites is
the most significant scientific issue we can address with
Opportunity at this time,” said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y., principal investigator for the
science instruments on both rovers. “We’ve read the last
chapter, the record of the final gasps of an evaporating body
of water. What came before? It could have been a deep-water
environment. It could have been sand dunes. It could have
been a volcano. Whatever we learn about that earlier period
will help us interpret the upper layer’s evidence for a wet
environment and understand how the environment changed.”

Richard Cook, project manager at JPL for the rovers, said
that reaching one exposure of the older rock layers inside
Endurance requires driving only about 5 to 7 meters (16 to 23
feet) into the 130-meter-diameter (140-yard-diameter) crater.
The rover is on the rim at that site, which had been dubbed
“Karatepe.”

“We’ll take an incremental approach, edging our way down to
the target,” Cook said. The plan is to use the tools on
Opportunity’s robotic arm to analyze the exposed layers for
several days, then drive in reverse back up the slope and
exit the crater. The slope between the rim and the layered
outcrop at Karatepe is about 25 degrees.

“We have done testing that says we can do 25 degrees,
provided the wheels are on a rock surface and not loose
sand,” Cook said. Engineers and scientists on the rover team
built a test surface mimicking the rocks and sand seen in
Opportunity’s images of Endurance Crater. The surface was
tilted to 25 degrees, and a test rover climbed it. If
portions of the route to the outcrop turn out to be between
25 and 30 degrees, the team plans to proceed slowly and use
Opportunity to assess the amount of traction the rover is
getting.

Opportunity and its twin, Spirit, successfully completed
their primary three-month missions on Mars in April.

JPL, a division of the California Institute of Technology in
Pasadena, manages the Mars Exploration Rover project for
NASA’s Office of Space Science, Washington. Images and
additional information about the project are available from
JPL at: http://marsrovers.jpl.nasa.gov