Curiosity has been on Mars for more than four years now, much longer than the primary mission of about 23 months. NASA builds ’em to last, though. Curiosity has sent back a wealth of data from Mars, but it can’t last forever. Indeed, it’s wheels are getting banged up, the ChemCam autofocus has gone wonky, and now Curiosity’s rock drill stopped working on December 1. Mission scientists have a better idea what’s going on with the drill, though they haven’t worked out if it’s fixable.
Curiosity has instruments to study the composition and structure of Martian geology, but it can only learn so much from scanning the surface. That’s why the rover was equipped with a percussion drill at the end of its 7-foot robotic arm. This allows Curiosity to extract samples from deeper layers of strata that haven’t been exposed the radiation on the surface. It’s been used to drill into 15 different targets so far. It’s an important tool for the rover as it climbs ever higher on Mount Sharp, so losing it would be a real blow to the mission.
The drill carries two spare drill bits in case one of them breaks, but the problem doesn’t appear to be the bit. Mission scientists originally narrowed the problem down to either the brake or electronic sensors that monitor the drill’s rotation. More recently, the issue has mostly been narrowed down to the brake. If they can’t get the brake to disengage correctly, the drill can’t be spun up.
The team had some success since the issue first appeared on December 1st. Curiosity was able to get the mechanism working by moving the drill feed around — I suppose that’s the rover equivalent of jiggling the handle. However, the problem came back a few days later. The team is still looking at ways to potentially fix the drill, but Curiosity is on its own out there. There’s no one around to walk over and give it a kick.
This isn’t the first time Curiosity has had issues with the drill. There have been a number of short circuits that temporarily took the drill offline. When and if the current drill issue is resolved, the team plans to be gentler with the tool. As a “percussion” drill, it’s able to both hammer and rotate. They’ll try to stick to just rotating whenever possible. Testing on Earth suggests that just rotating should be sufficient to bore into softer rocks.
Even if the drill can’t be completely fixed, Curiosity can still be of use on Mars. It’s already covered more distance than all past rovers, and carries plenty of atmospheric sensors and cameras.