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Perseverance on the rocks: Pebbles clog up the rover's Martian sample collection

Engineers try to clear material so Mars bot can continue drilling

NASA engineers have temporarily paused Perseverance’s ability to drill and collect Martian rock samples due to pebbles piling up in the rover’s caching system.

Perseverance, the largest and most complex human-built robot to roam the surface of Mars, is on the hunt for particularly interesting geological formations that could reveal if the Red Planet once supported ancient microbial life. Armed with an array of tools, the rover determines whether a rock specimen is worth collecting.

First, it drills into some rock using its robotic arm. The material attached to the drill bit enters a slot on a rotating carousel before the sample is put inside a tube and photographed. A third system extracts the tube, seals it, and stashes it away. Here’s a video demonstrating that process below.

Youtube Video

Perseverance was attempting to collect its sixth specimen before engineers noticed something was wrong. As the coring bit was coming into contact with the carousel component, they reported higher than normal levels of resistance.

“The sensor recorded higher resistance than usual at about 0.4 inches (1 centimeter) earlier than expected, and some much higher resistance than expected during the operation,” Louise Jandura, Chief Engineer for Sampling & Caching at NASA/JPL, confirmed in a blog post this month.

Images snapped inside its internal rock caching system revealed that there were “a few pieces of pebble-sized debris” inside the bit carousel. The fragments clogging up a slot inside the carousel meant that the core sample couldn’t fit as snugly inside. The team believes these Martian pebbles are flecks that fell out of the sample tube when the core slid out from under a drill bit.

NASA is now trying to figure out how to clear the pebbles from the bit carousel and has stopped Perseverance from drilling into new rock samples for now. “This is the first time we are doing a debris removal and we want to take whatever time is necessary to ensure these pebbles exit in a controlled and orderly fashion. We are going to continue to evaluate our data sets over the weekend,” Jandura said.

It’s not the first time Perseverance has run into issues. The rover's first attempt at bottling up a sample ended in failure when the rock it drilled crumbled into dust, although its instruments were not at fault that time. It's unclear when Perseverance will be able to resume collecting rocks, but NASA said given the position of the Red Planet at the moment data speeds to and from the rover are slower than usual.

"This is not the first curve Mars has thrown at us – just the latest. One thing we’ve found is that when the engineering challenge is hundreds of millions of miles away, it pays to take your time and be thorough," Jandura added. "We are going to do that here. So that when we do hit the un-paved Martian road again, Perseverance sample collection is also ready to roll." ®

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