Despite months of listening, NASA has failed to pick up any signals from the stalwart Opportunity rover.
The end of a space mission never comes easy.
After spending the past eight months attempting to make contact, NASA has formally announced the end of the Opportunity mission on Wednesday, February 13th. The team made last contact with the rover on June 10, 2018, prior to a planet-wide dust storm leading up to opposition last July.
Opportunity's mission was originally expected to last 90 days. It relies on solar panels for power, and engineers expected dust to accumulate on the panels over time and choke out that power. "We didn't expect wind to blow dust off," says project manager John Callas (NASA / JPL). "It became reliable on a seasonal cycle." Combined with what Callas calls "the finest batteries in the solar system," the robot far outlived its original warranty.
But now, after almost 15 years of roving the Red Planet, last summer's global dust storm proved too much for the rover to withstand. Dust coated the panels, and Opportunity's voltage dropped below usable levels. (The dust storm wasn't a problem for plutonium-powered Curiosity.)
The end of the mission doesn't come for lack of trying. NASA sent more than a thousand recovery commands to Opportunity since it lost contact last summer. Some thought the Deep Space Network had picked up a signal in August and again in November, which briefly raised hopes, but these weren't real detections. The partial U.S. government shutdown also put a pause on the hunt for Opportunity in January. NASA resumed a last-ditch effort over the past few weeks, assuming that one or both X-band radios on Opportunity had failed or that the rover had reset its internal clock and was instead responding on UHF frequencies. There was also slightly renewed hope that a small dust storm passing over Opportunity in early January might have cleaned off its dust-coated solar panels.
Now, NASA has declared the mission at an end. NASA lost contact with Opportunity's twin rover Spirit on March 22, 2010. Spirit had landed on the opposite side of Mars, and the mission came to an end after Spirit's wheel became stuck in soft Martian dirt. Spirit came to rest on the west side of Home Plate in the Columbia Hills region of Mars.
Requiem for a Mars Rover
Launched atop a Delta II rocket from Cape Canaveral Air Force Station in Florida on July 7, 2003, Opportunity used an innovative airbag-style landing, pioneered by Mars Pathfinder in 1997. The rover bounced to a stop on January 25, 2004, having scored a "hole-in-one" landing inside the 72-foot (22-meter) wide Eagle crater.
Opportunity then traversed a record-breaking 28.06 miles (45.16 kilometers) during its mission, farther than any other off-world rover, human or robotic. Opportunity surpassed the old distance record of 24 miles (39 kilometers) set by the Soviet Union's Lunokhod 2 in 1973, and crossed marathon distance of 26.2 miles on March 24, 2015. During its career, Opportunity journeyed to 750-meter Victoria crater in 2007, then onward to the 13.7-mile-wide Endeavour Crater in 2012, traversing its ridge and Marathon Valley between 2016 and 2017.
Opportunity's journey broke new ground in planetary geology and exploration. The rover was the first mission to characterize and identify a sedimentary rock record on a world other than Earth. In the Burns formation along the rim of Endurance crater, Opportunity discovered layers of sulfate-rich sandstone. The find pointed to a wet past, but as Steve Squyres (Cornell University) noted, "It wasn't 'water on Mars,' It was really 'sulfuric acid on Mars.'" The region Opportunity was exploring had formed under ancient, ephemeral playas, and wind and water erosion had reworked the area long ago. Opportunity also documented the mineral hematite, nicknamed "blueberries," providing additional evidence that water had once percolated through the rocks.
In 2008 Opportunity embarked on what was essentially a second mission, undertaking a 21-kilometer drive to Endeavour Crater. After three years on the road, the rover arrived to find older rocks laden with clay minerals, pointing to an earlier era when the water coursing through the rocks had been fit to drink.
Opportunity also examined a number of meteorites on Mars. One of these was Heat Shield Rock, which the rover found while it was examining its own heat shield, which had delivered it to the surface. Opportunity also explored the largest crater ever visited by a Mars rover (Endeavour), studied the oldest rocks seen by either rover, and found further evidence for ancient water erosion along the Cape York formation.
The end of Opportunity's Mars-roving days comes even as all too many missions are closing down: Dawn finished up at 1 Ceres in 2018 and Cassini finished up at Saturn in 2017. Curiosity soldiers on as the sole rover on Mars now, though it will soon have company: NASA's Mars 2020 rover and the European Space Agency's Exomars rover will head to the Red Planet during the next launch window in 2020.
Meanwhile, Opportunity will lie dormant on the rim of Endeavour Crater, a testament to human innovation and planetary exploration.
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