NASA’s Mars Opportunity rover began its latest adventure
today inside the martian crater informally called Endurance.
Opportunity will roll in with all six wheels, then back out
to the rim to check traction by looking at its own track
marks.
“We’re going in, but we’re doing it cautiously,” said Jim
Erickson, deputy project manager for the Mars Exploration
Rovers at NASA’s Jet Propulsion Laboratory (JPL), Pasadena,
Calif. Barring any surprises, Opportunity will enter the
stadium-sized crater Wednesday for two to three weeks of
scientific studies.
Click on image to enlarge
“NASA has made a careful decision. The potential science
benefits of sending Opportunity into the crater are well
worth the calculated risk the rover might not be able to
climb back out,” said JPL’s Dr. Firouz Naderi, manager of
NASA’s Mars Exploration Program. “Inside the Endurance crater
waits the possibility for the most compelling science
investigations Opportunity could add to what it has already
accomplished. We have done the ground testing necessary to
evaluate the likelihood of exiting the crater afterwards,” he
said.
“Spirit and Opportunity are well into their bonus periods
after successfully completing their three-month primary
missions in April,” Naderi said. “Both rovers are starting
new chapters. Spirit is within a stone’s throw of Columbia
Hills, and Opportunity is entering the crater.”
Dr. Steve Squyres of Cornell University, Ithaca, N.Y., the
rovers’ principal investigator, said, “We expect the science
return of going a short way into Endurance to be very high.”
The target for inspection within the crater is an exposure of
rock layers beneath a layer that corresponds to rocks
Opportunity previously examined in the shallower Eagle
crater, where the rover landed in January.
The sulfur-rich layer seen in Eagle yielded evidence a body
of gently flowing water once covered the area. The underlying
layers come from an earlier period. Opportunity’s
observations from the rim of Endurance already have shown
their composition differs from the Eagle crater’s layers.
“If there was a change in rock type, there was a change in
environment,” Squyres said. “This unit will tell us what came
before the salty water environment the Eagle crater unit told
us about. We want to get to the contact between the two units
to see how the environment changed. Is it gradual? Is it
abrupt?” Even if the lower layers formed under dry
conditions, they may have been exposed to water later. The
water’s effect on them could have left telltale evidence of
that interaction,” he said.
One section of the target outcrop is only five to seven
meters (16 to 23 feet) from the rim in an area dubbed
Karatepe. The rover team’s plan is to get there, examine the
rocks for several days, and then exit the crater. Reaching
lower-priority targets, like at the bottom of the crater,
would entail driving on sand, with a higher risk of not
getting out again.
The strategy for driving on the crater’s inner slope is to
keep wheels on rock surfaces instead of sand, said JPL rover-
mobility engineer Randy Lindemann. The team ran trials with a
test rover on a surface specifically built to simulate
Karatepe’s surface conditions. “The tests indicate we have a
substantial margin of safety for going up a rocky slope of 25
degrees,” Lindemann said. Opportunity’s observations from the
rim at the top of the planned entry route show a slope of
less than 20 degrees.
Spirit, launched one year ago Thursday, has driven more than
3.2 kilometers (2 miles) inside the Gusev Crater. A trench it
dug in May exposed soil with relatively high levels of sulfur
and magnesium, reported Dr. Johannes Brueckner, of Max-
Planck-Institut fuer Chemie, Mainz, Germany. Spirit’s alpha
particle X-ray spectrometer showed concentrations of these
two elements varied in parallel at different locations in the
trench, suggesting they may be paired as a magnesium sulfate
salt.
Squyres said, “The most likely explanation is water
percolated through the subsurface and dissolved out minerals.
As the water evaporated near the surface, it left
concentrated salts behind. I’m not talking about a standing
body of water like we saw signs of at Eagle crater, but we
also have an emerging story of subsurface water at Gusev,” he
said.
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.
For images and information about the Mars project on the
Internet, visit:
