After 1,856 Martian days among blue sunsets, sand dunes and small, lumpy moons, the Mars rover Curiosity sat on the ridge of an ancient lake bed and looked back on its five-year-long journey so far.
NASA has released a composite photo of what Curiosity saw in October, and if the rover could breathe, it might gasp. In one image was its whole story: from the lower slopes of Mount Sharp, where it sat holding its camera, to the spot in the crater floor 11 miles distant, where it had touched down five years earlier to great celebration on Earth.
As the most complex NASA instrument ever put on Mars, with its drill, laser and chemistry set, Curiosity has sometimes disappointed those who would mine its data for research. A NASA panel even chastised its operators for doing more sightseeing than science.
Maybe for the same reason, Curiosity has brought Mars to life for the public. The soil data it has collected suggest Mars was once a beautiful planet of rivers and lakes. But the rover's many postcards of eclipses, dust devils and shimmering sands showed the world it's a beautiful place, even now.
From the ridge on which Curiosity sat late last year to take its panorama photos, it could see the treacherous Bagnold Dunes it had crossed months before. The rover reached the dune field on the 1,174th Martian day, or sol, of its mission (late 2015 on Earth) and spent months navigating between them. These mounds of windblown sand stretched for miles and were one of the greatest barriers between Curiosity and its destination – Mount Sharp, toward the crater's interior.
By the end of 2016, Curiosity had cleared the dunes and was rolling across veins of gypsum. Attending to its scientific duties, the Washington Post wrote, the rover used its laser to detect traces of boron in the rock, suggesting a habitable lake once covered the crater floor.
Then it turned toward Mount Sharp and began to climb its lower ridges, where it now sits.
Before crossing the dunes, Curiosity spent months traversing the foothills beneath Mount Sharp. It reached the Pahrump Hills on sol 753 – in September 2014 – and by the end of the year had excited scientists with the first definitive evidence of organic matter on Mars, raising hope that life might once have swum in alien waters.