After six months of exploring the inside of a stadium-sized Martian crater, the seemingly never-ending story of NASA's Opportunity rover continues with a trek across the Martian plains. New goals and new discoveries are already in sight.
Photographs released on Sunday show new views of the Martian plains, taken by the robot as it cleared the rim. One of the latest images shows a white object, the goal of Opportunity's next traverse.
This artificial structure is not some alien monument, but the probe’s own heat shield, released moments before its landing almost a year ago. Scientists are eager to examine both the shield and the deep hole it gouged into the ground.
How it got this far
Opportunity landed on Mars on Jan. 24, bouncing across Meridiani Planum and coming to rest within a 20-meter-wide (65-foot-wide) crater. Designed for a 90-day primary mission, the rover rolled across a cratered plain, examining rocks and small craters.
On June 10, long after its 90-day "warranty" had lapsed, Opportunity stood on the edge of a crater whose walls were lined with sedimentary rocks that promised to contain secrets of the early eons of Mars. After weighing the risks and potential payoffs, scientists sent the wheeled robot over the edge and into the crater.
Over the months that followed, Opportunity defied the depths of the Martian winter, a communications gap when Mars passed behind the sun, the minor aches and pains of aging hardware, and a growing burden of choking dust that slowly strangled the flow of electrical power from its solar energy panels. It drilled holes, sampled rocks and dust, and sent back pictures ranging from microscopic-scale detail shots to stunning panoramas.
Controllers at NASA's Jet Propulsion Laboratory faced steep, slippery slopes and crumbly soil where the six wheels turned as uselessly as auto wheels spinning in snow and ice. Planners also had to keep the rover’s top edged to the north to maximize the sunlight falling on the solar panels.
“The rover was pushed to its traverse limits, but continued to perform all that was asked of it,” mission planners said in a recent status report. “Opportunity remains in excellent health,” they said, adding that “solar power is nearly as high now as it was at the beginning of the mission.” Somehow the dust was not accumulating as fast as hoped, or was being shaken off by the rover’s frantic motions.
The crashed flying saucer
The rover mission's principal investigator, Steven Squyres of Cornell University, described the team’s plans in a recent interview with Astrobiology magazine.
”We've got a lot of things ahead of us,” he explained. “The first thing we're going to do is get to the heat shield. We've been itching to go to this thing for months now.”
The disk-shaped shield hit the ground at about 200 miles per hour. “It's going to look like a crashed flying saucer out in the desert,” Squyres joked.
”We want to look down into whatever hole it dug,” he said. “It's probably deeper than any hole that we can dig with our wheels.
Examining the shield itself will also help design future Mars probes, he added. This is important, he explained, because “no one's ever been able to examine a heat shield that's gone through the Martian atmosphere.” The rover will use its microscope to document the effects of the heat shield's fiery passage through the atmosphere — and the data could help designers craft thinner, lighter, more efficient shielding.
Squyres estimated that the heat shield was about 500 feet (150 meters) away.
Over the horizon
A few specific local science experiments will also now be possible. “There are a few cobbles — little fist-sized rocks scattered about the plains — and we've never looked at one,” Squyres told Astrobiology magazine. “So we're going to find out what those rocks are made of.”
The probe will then roll south, probably for the rest of its life. About a mile and a half (2.5 kilometers) away begins a region of what is called “etched terrain,” broad striped regions that are thought to represent different levels of sediments. Analyzing those layers could provide further insights about Mars' geological history.
About 2 miles (3.2 kilometers) even farther away is Victoria Crater, six times bigger than Endurance Crater. That may prove to be “one crater too far” — unreachable in any reasonable rover lifetime. But Opportunity and its twin rover Spirit, on the other side of the planet, already have shown surprising endurance, and there may be more surprises yet to come.