Taking the plunge: Victoria Crater in Mars' Meridiani Planum contains an exposed layer of bright rocks that may contain evidence of interaction between the Martian atmosphere and surface from millions of years ago.

Credit: NASA

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SYDNEY: Two months after dust from severe storms darkened the skies and nearly killed NASA's Mars exploration rovers, the solar-powered robots are awake and ready to start work afresh.

"These rovers are tough. They faced dusty winds, power starvation and other challenges – and survived. Now they are back to doing groundbreaking fieldwork on Mars. These spacecraft are amazing," said Alan Stern, associate administrator of the U.S. space agency's Science Mission Directorate in Washington, DC.

During July Martian dust storms blocked so much sunlight that researchers grew concerned the rovers' daily energy supplies could plunge too low for survival. Engineers at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, put Opportunity onto a very low-energy regimen of no movement, few observations and reduced communication with Earth.

Beneficial wind gusts

Dust from the sky had been falling onto both rovers' solar panels, impeding their ability to collect energy from the sun. However, beneficial wind gusts removed some of the new build-up from Opportunity almost as soon as it accumulated.

Skies above both rovers remain dusty but have been clearing gradually since early August. The rovers are now 43 months into missions originally planned to last just three months.

Last week, Spirit climbed onto Home Plate, a plateau of layered bedrock bearing clues to an explosive mixture of lava and water. Opportunity's planned descent into the Red Planet's giant Victoria Crater was delayed, but now the rover is preparing to drive into the 730-metre-wide pockmark sometime this week.

Opportunity drove to the rim in late August and examined possible entry routes. Last week, the rover began to approach its planned entry point. The route will provide better access to a top priority target inside the crater: a bright band of rocks about 12 metres from the rim.

"Toe dip"

"We chose a point that gives us a straight path down, instead of driving cross-slope from our current location," said Paolo Bellutta, a JPL rover driver plotting the route. "The rock surface on which Opportunity will be driving will provide good traction and control of its path into the crater."

For its first foray into the crater, Opportunity will drive just far enough to get all six wheels in; it will then back out and assess slippage on the inner slope. "Opportunity might be ready for that first 'toe dip' into the crater as early as [this] week," added JPL's John Callas, rover project manager. "In addition to the drives to get to the entry point, we still need to conduct checkouts of two of Opportunity's instruments before sending the rover into the crater."

Victoria Crater contains an exposed layer of bright rocks that may preserve evidence of interaction between the Martian atmosphere and surface from millions of years ago, said the researchers.