Six years ago, NASA?s Mars rovers Spirit and Opportunity touched down on the red planet with a team of scientists eagerly looking ahead to their short, three-month missions.
As they embark on their seventh year on Mars, the longevity of the plucky rovers continues to amaze their minders back on Earth, even with Spirit potentially permanently stuck wheel-deep in Martian sand.
Spirit set down at Gusev Crater on Jan. 3, 2004, at 11:35 p.m. EST, with its younger sister rover Opportunity landing on the other side of the planet ? on the plains of Meridiani Planum ? more than two weeks later at midnight EST on Jan. 25. While Sunday marks the mission?s sixth anniversary on Earth, it has only been 3.2 Martian years since one year on Mars is about 687 Earth days long.
Originally slated to trundle across the Martian surface for only 90 days each, Spirit and Opportunity blew past those deadlines and have continued their missions for far longer than mission engineers ever thought possible. Opportunity even passed the 11-mile mark on its odometer earlier this year and beamed home more than 132,000 images of Mars.
?They?re all so far out of warranty,? said Ray Arvidson of Washington University in St. Louis. Arvidson is deputy principal investigator for the science payloads on Spirit and its twin.
The observations by the two rovers over the course of their six years on Mars have substantially shaped our understanding of the nature and evolution of the Martian surface, particularly by supplying ample evidence that at least portions of the Martian surface were once wet.
But the going hasn?t always been smooth.
Spirit has had a particularly rough go of it, suffering a set of computer glitches after landing, and coming close to a chilly demise last year as its power levels dwindled during the dark Martian winter.
The latest challenge to beset the rover is a sand trap that Spirit fell into on May 6 as it moved away from a rocky plateau called Home Plate to a pair of targets 600 feet (180 meters) away. The rover?s wheels fell through a thin layer of crust and became stuck in the sand below. Mission engineers have been working sine then to spin Spirit?s wheels to extract her.
Spirit?s situation hasn?t been entirely negative though, as its stuck wheels have churned up dirt with interesting properties that suggest the site once hosted hydrothermal vents.
Opportunity, meanwhile, has discovered its third meteorite on the Martian surface during its ongoing trip to the monster crater Endeavor, which is about 7 miles (12 km) away and nearly 14 miles (22 km) wide.
What will happen to the rovers and what they will find as they begin their seventh year on Mars is anybody?s guess, though mission managers are concentrating on freeing Spirit and getting her into a better position before winter sets in on the red planet.
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