Opportunity really is the little Mars rover that could (and still does). It's been eight years and the rover is closing in on an achievement many humans don't realize: it is just 4.2 miles away from rolling a full 26.2 mile marathon. This is, of course, not including the 283 million miles the rover flew through space to reach Mars in the first place.
Opportunity, along with its twin rover Spirit, arrived on Mars in 2004. The pair were built to roam the Martian surface in search of evidence of water in Mars' history. Scientists suspect that, although Mars is a cold, dry world today, it was once wet, warm, and possibly home to some kind of life forms (think bacteria more than Marvin the Martian).
Spirit and Opportunity landed on opposite sides of the planet at geologically interesting areas. Each was designed to last just three months during which time they would drive a little less than 2,000 feet a piece. Spirit went further, operating for six years before falling silent in 2010. Opportunity has exceeded that by a lot. It's gone more than sixty times its planned distance.
Twenty-two miles in eight years might not sound impressive, but you have to consider how hard it is to drive a vehicle remotely on Mars. Mars is on average more than 30 million miles away from the Earth and it takes commands 20 minutes to travel that distance. Drivers can only direct the rover as far as they feel safe, usually using pictures from the rover's camera as a guide. After all, there aren't gas stations to fix a broken wheel on Mars; scientists have one chance to navigate around, say, a big rock. It pays to be careful.
Opportunity typically travels between 160 and 320 feet each drive day. Even moving at that glacial pace, the rover has visited some impressive sites on Mars, returned some amazing science, and more than 100,000 pictures.
The rover landed inside Eagle crater – a real planetary hole in one. When it opened its eyes (which means it turned on its camera and sent pictures to Earth) it found rocks that looked like they were formed in a shallow lake. The rover manoeuvered out of Eagle crater and trundled along to the nearby Endurance crater, visited the larger Victoria crater and the Santa Maria crater before arriving at Spirit point in August 2011.
Named for Opportunity's twin rover, Spirit point sits on the edge of the massive, 14 mile wide Endeavour crater.
“Endeavor is surrounded by fractured sedimentary rock, and the cracks are filled with gypsum. Gypsum forms when ground water comes up and fills cracks in the ground, depositing hydrated calcium sulfate," explains Ray Arvidson, Mars Exploration Rover Mission deputy principal investigator. In short, gypsum needs water to form, so its presence is indicative of past water on Mars. "This is the best evidence we’ve ever found for liquid water on Mars,” he said. Arvidson added that the team has no plans to stall Opportunity's momentum.
Despite covering an impressive amount of the Martian surface, the honour of longest distance traveled by a robotic vehicle belongs to the Soviet Lunokhod 2. Launched on January 11, 1973, the rover landed on the Moon on January 15. It covered 23 miles in four months before going silent on June 4.
Opportunity isn't far from breaking Lunokhod 2's record, and Curiosity might challenge the distance record a few years from now. After landing on August 5, the rover will begin its exploration of the surface. During its two year primary mission, the rover is expected to travel 12 miles. But if Curiosity's heritage is any indication of its future success, this rover will likely live well beyond its expected lifetime. The rover's power source will keep the it running for up to 14 years. So barring some technical setback, we might see Curiosity roll an ultra-marathon on Mars.