"Calculated Risk" Could Be Long-Lived Rover's Last Mission
It could be the final mission for NASA's Mars rover
Opportunity... but even if it is, it's worth it. Scientists at the
Jet Propulsion Laboratory tell ANN Opportunity is scheduled to soon
begin a descent down a rock-paved slope into the Red Planet's
massive Victoria Crater.
Opportunity already has been exploring layered rocks in cliffs
around Victoria Crater. The team has planned the descent carefully
to enable an eventual exit, but Opportunity could become trapped
inside the crater or lose some capabilities. The rover has operated
more than 12 times longer than its originally intended 90 days.
The scientific allure is the chance
to examine and investigate the compositions and textures of exposed
materials in the crater's depths for clues about ancient, wet
environments. As the rover travels farther down the slope, it will
be able to examine increasingly older rocks in the exposed walls of
the crater.
"While we take seriously the uncertainty about whether
Opportunity will climb back out, the potential value of
investigations that appear possible inside the crater convinced me
to authorize the team to move forward into Victoria Crater," said
Alan Stern, NASA associate administrator, Science Mission
Directorate, NASA Headquarters, Washington. "It is a calculated
risk worth taking, particularly because this mission has far
exceeded its original goals."
The robotic geologist will enter Victoria Crater through an
alcove named Duck Bay. The eroding crater has a scalloped rim of
cliff-like promontories, or capes, alternating with more gently
sloped alcoves, or bays.
A meteor impact millions of years ago excavated Victoria, which
lies approximately four miles (six kilometers) south of where
Opportunity landed in January 2004. The impact-created bowl is half
a mile (800 meters) across and about five times as wide as
Endurance Crater, where Opportunity spent more than six months
exploring in 2004.
The rover began the journey to Victoria from Endurance 30 months
ago. It reached the rim at Duck Bay nine months ago. Opportunity
then drove approximately a quarter of the way clockwise around the
rim, examining rock layers visible in the promontories and possible
entry routes in the alcoves (you can see the rover's tracks at the
top of the above image.) Now, the rover has returned to the most
favorable entry point.
"Duck Bay looks like the best candidate for entry," said John
Callas, rover project manager at JPL. "It has slopes of 15 to 20
degrees and exposed bedrock for safe driving."
If all its six wheels continue working, engineers expect
Opportunity to be able to climb back out of the crater. However,
Opportunity's twin rover, Spirit, lost the use of one wheel more
than a year ago, diminishing its climbing ability.
"These rovers are well past their design lifetimes, and another
wheel could fail on either rover at any time," Callas said. "If
Opportunity were to lose the use of a wheel inside Victoria Crater,
it would make it very difficult, perhaps impossible, to climb back
out."
"We don't want this to be a one-way trip," said Steve Squyres,
principal investigator for the rovers' science instruments, Cornell
University, Ithaca, NY. "We still have some excellent science
targets out on the plains that we would like to visit after
Victoria. But if Opportunity becomes trapped there, it will be
worth the knowledge gained."
The Jet Propulsion Laboratory manages the Mars Exploration Rover
project for NASA's Science Mission Directorate.