Controllers Testing Ways To Get Out
The Opportunity Rover
bogged down in a 12-inch tall sand dune recently, leaving
controllers with a challenge. The four corner wheels of the rover
are about half buried into the dune, but the rover is otherwise in
"We choose to proceed cautiously, so we don't expect to begin
actually driving out of the dune before next week, possibly later,"
said Jim Erickson, rover project manager at JPL in a statement.
"Both Opportunity and Spirit have already provided many more months
of scientific exploration than anyone expected. By taking good care
of them, we hope to keep them exploring for more months to come.
Tests so far have sustained our optimism about Opportunity's
ability to drive out of this dune, but we have more testing ahead
to understand how robust that capability is."
Opportunity had driven about 131 feet of a planned 295-foot
drive when the wheels began slipping. The rover was driving
backwards when it began to dig itself into the small dune.
Eventually, the rover sensed that something was wrong and it
stopped trying to move. It is on the ridge of a small ripple of
soft sand. (NASA Mosaic Image below)
"We've climbed over dozens of ripples, but this one is different
in that it seems to be a little taller and to have a steeper slope,
about 15 degrees on part of its face," said Mark Maimone, a JPL
rover mobility engineer.
Engineers are using a lab and various sandy and powdery
materials to simulate the situation at NASA's Jet Propulsion
Laboratory in Pasadena, California. A test in a simulated sand dune
proved to be no challenge for the test rover to escape, but a finer
and looser material was needed for more realistic tests.
Raiding several home supply and hardware stores, scientists
managed to find enough play sand, diatomaceous earth, and mortar
clay powder to make more than two tons of simulated Mars sand.
"We needed to do tests using material more like what Opportunity
is in, something that has a fluffier texture and cakes onto the
wheels," said JPL rover engineer Rick Welch, who is leading the
"We found that when the wheels dig in, the material we're using
does stick to the wheels and fills the gaps between the cleats, but
it doesn't stick when you're just driving over it. That's good
because it's the same as what we see in the images from
Opportunity," said Dr. Robert Sullivan of Cornell, a rover science
team member who has helped to match the test sand.
Initial experiments seem to show that a test rover positioned
like Opportunity can drive out after spinning its wheels at first.
Of course, more testing will be done before any commands are sent
to the Rover.
While waiting, Opportunity has been looking around with its
cameras. It has traveled more than 3.32 miles in the 15 months
since landing on Mars.