On August 6, 2012, the Curiosity Rover landed on Mars, in a huge depression called Gale Grater.
Just over two years later, the rover has traveled about 5.5 miles, and NASA scientists announced that it is finally nearing its main destination: a large mountain at the crater's center called Mount Sharp.
Mount Sharp is so appealing because scientists believed its exposed rock layers were formed over the course of tens of millions of years. As the rover climbs up the 18,000-foot mountain over the next few years and samples these layers, it could tell us a ton about Mars' environmental history and provide new information about whether it might have once been capable of supporting life.
Curiosity's first year on Mars was something of a detour, as scientists sent it to an area called Yellowknife Bay, where it found tantalizing evidence of an ancient freshwater lake and identified chemical elements that could have once served as building blocks for life.
Afterward, NASA scientists refocused on the goal of reaching Mount Sharp, and directed Curiosity back in the mountain's direction. The rover is now at its base, and will crawl parallel to the mountain for about two miles before turning and heading uphill.
Scientists have repeatedly altered Curiosity's route toward the mountain because of excessive damage to its wheels caused by jagged rocks, as well as the difficulty it has had crossing loose sand. Last week, they announced a new route that will serve as a shortcut to the mountain — minimizing further damage — and also take the rover to a geologically interesting area where the mountain's rock layers meet those of the surrounding crater.
Afterward, Curiosity will climb Mount Sharp. The possibility that the mountain could preserve millions of years of Martian history in exposed rock layers is the reason the rover landed in Gale Crater in the first place, and the whole mission was designed largely around the objective of sampling these rocks.
Scientists hope that this mission will help us better understand how Mars' environment evolved over time. It's believed that the planet may have once had a thicker atmosphere that allowed liquid water to form and protected its surface from radiation and asteroid impacts. Of course, that's no longer the case — but the rocks might help us understand what happened to that atmosphere, and if Mars' historical conditions may have once allowed life to evolve.