Yee-haw! After perching near its tip for days, NASA's Mars rover Curiosity rode down the largest sand dune it has ever attempted on the Red Planet.
"I'm over the moon that I'm over the dune!" the rover's Twitter account tweeted Thursday.
Rover driver Matt Heverly at Jet Propulsion Laboratory tweeted his relief.
"Seeing this picture from the bottom of the sand dune put an even bigger smile on my face today," Heverly wrote.
Riding this dune, about a yard high and 10 yards long, was risky, but the engineers on the Mars Science Laboratory mission had led Curiosity here for a reason. Late last year the team noticed that its aluminum wheels had suffered an alarming amount of holes, scratches and other damage. The terrain on their path, called the "rapid transit route," was too rough for the wheels to handle.
"That gave us concern," said Curiosity's lead scientist, John Grotzinger, a Caltech geologist. "We expect to get damage to the wheels, but we were surprised at the rate."
The scientists have a few theories as to why Curiosity is running into this problem when previous rovers on other parts of the planet have not, Grotzinger said. They think the wind in Gale Crater tends to sharpen rocks to piercing points, and Curiosity is so much heavier than its predecessors that all that weight on those pointy rocks can really do some damage.
So the scientists took a sharp detour toward a more promising route; the only problem was the dune-filled Dingo Gap, a narrow passageway between two scarps that stood in their path.
The scientists were well aware of the risks of riding the dune. Both 2004 rovers Spirit and Opportunity got themselves into sticky situations when crossing sand. Opportunity got so stuck in a sand dune in 2005 that scientists called the spot Purgatory, and Spirit became mired in a sand trap in 2009, from which it never recovered.
Now, having ridden its largest sand dune yet, Curiosity is heading west to a new frontier and a new possible drill target: a spot called KMS-9, which could host a whole different habitable environment from the life-friendly spots in Yellowknife Bay.