Ejecting Mars’ Pebbles

The team has made good progress implementing the initial recovery steps outlined in last week’s blog. Our first success: The upper two pebbles were ejected from the bit carousel during a test. 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. Our second success: We appear to have removed most – if not all – of the cored rock that remained in Sample Tube 261.

Here is the latest…

Pebbles in Bit Carousel

On Monday, Jan. 17, the WATSON camera imaged the bit carousel and its pebbles – and also took images underneath the rover to establish just what was down there before any recovery strategies were applied. Later that same Martian day, we rotated the bit carousel about 75 degrees before returning it back to its original position. WATSON imaging showed the two upper pebbles were ejected during the process. Tuesday night we also received the second set of under-rover images, which show two new pebbles on the surface, indicating the ejected pebbles made it fully through bit carousel and back onto the surface of Mars as planned.

The other two pebbles, located below the bit carousel, remain. It is interesting to note that some of the initial trials performed on our testbed here on Earth indicate that the location of the two leftover pebbles may not pose a significant problem with bit carousel operation, but we are continuing analysis and testing to confirm this.

Remaining Sample in Tube

On Saturday, Jan. 15, the team performed an experiment using Perseverance’s rotary-percussive drill. After the robotic arm oriented the drill with Sample Tube 261’s open end angled around 9 degrees below horizontal, the rover’s drill spindle rotated and then extended. Our remarkable Mastcam-Z instrument (which has video capability previously used to document some of Ingenuity’s flights) captured the event. The imagery from the experiment shows a small amount of sample material falling out of the drill bit/sample tube. Later that same Martian day, the bit was positioned vertically over “Issole” (the rock that provided this latest core) to see if additional sample would fall out under the force of gravity. However, Mastcam-Z imaging of 261’s interior after this subsequent maneuver showed it still contained some sample.

Given that some of the sample had already been lost, the team decided it was time to return the rest of the sample to Mars and hopefully completely empty the tube to ready it for potentially another sampling attempt. On Monday, Jan. 17, the team commanded another operation of the rotary percussive drill in an attempt to dislodge more material from the tube. 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. Mastcam-Z imagery taken after the event shows that multiple pieces of sample were dumped onto the surface. Is Tube 261 clear of rock sample? We have new Mastcam-Z images looking down the drill bit into the sample container that indicate little if any debris from the cored-rock sample remains. The sample tube has been cleared for reuse by the project.

Future Moves

The team is still reviewing the data and discussing next steps. Like all Mars missions, we’ve had some unexpected challenges. Each time, the team and our rover have risen to the occasion. We expect the same result this time – by taking incremental steps, analyzing results, and then moving on, we plan to fully resolve this challenge and get back to exploration and sampling at Jezero Crater.

Written by Rick Welch, Deputy Project Manager at NASA's Jet Propulsion Laboratory