NASA was flummoxed last week when the Perseverance rover attempted to collect its first rock core sample only to find the sample tube empty. The missing core was nowhere to be found, so the team had to take a step back and assess the situation on Mars. Now, NASA believes it has worked out what happened, and it’s ready to set course for the next sampling location.
The Perseverance rover has a suite of advanced instruments to study the red planet, including 23 cameras, an ultraviolet spectrometer, and ground-penetrating radar. However, you can’t send every possible instrument to Mars. Some of them won’t fit on a rover, and the team might not think to add others until the robot is already off on its mission. That’s why NASA designed the Sample Caching System, which lives on the underside of the rover.
One of Perseverance’s main goals is to drill rock core samples and store them in special tubes within the caching system. Eventually, another mission will meet up with the robot to pick up the tubes, launch them into space, and then another mission will return that package to Earth. First, we need to collect the samples, and that has been less straightforward than NASA expected.
Initially, all signs were good after the first sample collection. The robot’s drill (above) reached the correct depth, and the sample tube was stowed by the Adaptive Caching Assembly. However, the data that arrived several hours later showed nothing in the tube. The missing rock was not attached to the drill, nor was it on the ground near the rover. The team now believes the lack of samples is down to the peculiar nature of the rock chosen.
A closer examination of the drill hole shows some crushed material at the bottom. That could mean the drill simply pulverized the rock instead of producing a solid core. That means the sample is still in the hole and in the cuttings pile around it. NASA tested the drill on more than 100 rocks here on Earth, so this is not believed to be an issue with the hardware. It was just very bad luck that NASA chose a section of rock that was not robust enough to produce a core.
NASA’s solution is to give it another shot in a different location. The rover is setting course for South Seitah, where it will probably find more solid sedimentary rocks that won’t crumble under pressure. Perseverance has a few dozen more sample tubes to fill, after all.
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