NASA: Engineers try to retrieve Mars rover by Earth test

Aiming to retrieve the Mars rover Opportunity, engineers are using a testing laboratory to simulate Mars surface conditions, the Jet Propulsion Laboratory (JPL) of US space agency NASA said on Friday.

Careful test is necessary before any commands for Opportunity to move and continue exploring. The rover has plunged in a small dune days ago, said the JPL in a statement.

The rover team has cooked up recipes combining various sandy and powdery materials for the best simulation on Earth of the dune where Opportunity dug itself into wheel-hub depth last week.

Opportunity had driven about 40 meters of a planned 90-meter drive on the rover's 446th martian day when its wheels began slipping on April 26. The rover was driving backwards then.

The team frequently alternates between backwards and forwards driving to keep wheel lubrication well distributed. The wheels kept rotating enough times to have covered the rest of the distance if they hadn't been slipping, but it eventually barely inched forward. After a turn at the end of the planned drive, Opportunity sensed that it had not turned properly and stopped moving.

"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.

"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 is positioned across the ridge of an elongated dune or ripple of soft sand that is about one-third meter tall and 2.5 meters wide. Engineers said this ripple 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.

Last week, engineers arranged a simulated dune using sand that was already at JPL's rover testing facility and put a test rover into a comparably dug-in position. The test rover had no difficulty driving away, even when sunk in belly-deep.

However, that sand offered better traction than the finer, looser material that appears to make up the surface at Opportunity's current position.

Testing with different mixtures, engineers and scientists came up with a recipe that includes play sand for children's sandboxes, diatomaceous earth for swimming pool filters and mortar clay powder. Then they simulated Mars sand for more realistic mobility tests.

Experiments indicate that in this more powdery material, the test rover positioned comparably to Opportunity can drive out after some initial wheel-spinning. But more testing, analysis, planning and review will precede any actual commands for Opportunity to begin driving away from the dune.

Meanwhile, Opportunity has been using its cameras to study its surroundings at the edge of a region called "Etched Terrain."

Since landing more than 15 months ago, it has driven 5.35 kilometers.

NASA's another rover, Spirit, halfway around Mars, has recently been using all of its research tools to examine an outcrop called "Methuselah," the first outcrop of layered rock that Spirit has found.

The rover, after driving a total of 4.31 kilometers, has also been taking short movies of dust-carrying whirlwinds called "dust devils," the JPL said.

Source: Xinhua

People's Daily Online ---