Science

NASA Mars rover dumps pesky pebbles that were clogging its sampling system

Good riddance, rocks.

These pebbles interfered with the Perseverance rover's ability to stow away a rock sample tube.
NASA/JPL-Caltech/MSSS

This story is part of Welcome to Mars, our series exploring the red planet.

When Mars gives you pebbles, you give them back. 

NASA's Perseverance rover ran into a problem with its sampling process late last year when some pebbles got in the way of transferring a tube full of rock into its internal handling system. That meant the rover team had to get creative with clearing the blockage. 

The issue occurred along the rover's bit carousel, which passes the sample tubes inside for processing. As a test, NASA commanded the rover to rotate the carousel. It worked. The upper two pebbles were kicked out. "This is great news, as these small chunks of debris are believed to be the cause of the unsuccessful transfer of the drill bit and sample tube into the carousel back on Dec. 29," deputy project manager Rick Welch wrote in a mission update on Friday.

NASA tweeted a nifty GIF showing before and after views of the bit carousel. You can see how the largest pebbles are now cleared out.

There's still a small amount of debris left, but it may not cause any issues for the sampling process and those bits could fall out when the rover moves about.

Jettisoning the pebbles was just one task the rover needed to accomplish. The team also decided it would be smart to empty any remaining rock out of the sample tube so it could be reused for a fresh sample if needed. This experiment took a bit of effort as the team tried different methods of clearing the tube, including aiming it toward the ground. "With the tube's open end still pointed towards the surface, we essentially shook the heck out of it for 208 seconds – by means of the percussive function on the drill," Welch said.

The rover examined its handiwork and spotted some rock bits on the ground. Follow-up images show the tube can be reused, possibly for re-sampling the original rock that kicked off the pebble problem. 

Collecting rock samples is a key part of Perseverance's work. NASA is planning a future follow-up mission to gather the samples and bring them back to Earth for study.

The saga of the pebbles is a good illustration of the flexibility and creativity required for a robot to successfully operate on Mars. The unexpected can happen, like when the rover's flying helicopter companion Ingenuity was recently grounded due to bad weather. With some rotations and some shimmies, it looks like Perseverance will get back to building its rock collection fairly soon.