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One of the primary missions for NASA’s Mars rover, Perseverance, is looking for evidence of past life. Some of that evidence is hidden away deep inside of Martian rocks.

That’s what led Perseverance to drill into one particular briefcase-sized rock and, for the first time during its still-young mission, collect a core sample. Images and data that NASA received on Sept. 1 confirmed that the rover’s first coring attempt was (probably) a success.

There’s a whole process here that starts with a more superficial look at the Mars surface. Perseverance is fitted with several tools for interacting with the environment, including a Rock Abrasion Tool (RAT), which is “a high-speed grinder with brushes to remove that weathered outer layer of rock and clear away dust,” and a Gaseous Dust Removal Tool (GDRT) that, as its name suggests, clears away the dust at the site of the abrasion.

This first part of the process gives the rover an opportunity to use some other built-in instruments to examine the targeted rock even more closely. The data gathered from there helps NASA engineers decide if it’s worth moving on to the next step of trying to obtain a core sample.

This whole process unfolded earlier in August, which led in turn to Perseverance’s first attempt to core a Martian rock. Things didn’t go according to plan that time, as NASA explained in an Aug. 11 post.

While the rover’s seven-foot drill successfully bored its way into the rock and seemed to come away with a sample, images beamed back to Earth showed an empty storage tube. Unfortunately, that revelation occurred only after the tube was sealed and stored for future retrieval. It turned out that the rock itself wasn’t the best candidate for coring.

For the latest attempt, which appears to have been a success, the NASA team back on Earth learned from their earlier experiences. This time, they used one of the Perseverance rover’s onboard cameras, Mastcam-Z, to snap an image of the sample tube — or at least, the top of it — before sealing it away for storage.

The first look is encouraging, with actual rock clearly visible in the open end of the sample tube. But that’s only the first step before storage. Once a sample is collected, the rover kicks off a procedure called “percuss to ingest” which rattles the sample tube five times in brief, one-second bursts. The goal is to clear any excess residue from the lip of the tube, but that shaking can also send collected material deeper down.

That appears to be what happened here. While NASA’s first shot of the tube’s open end clearly shows there’s something inside, a second shot, captured after the “percuss to ingest” process, shows only a dark space.

Again heeding the lessons of the first coring attempt, NASA isn’t quite ready to call this coring operation a total success. Before the tube gets sealed off for storage, the Mastcam-Z will go to work once again “at times of day on Mars when the Sun is angled in a more favorable position.” The hope is that a new crop of images taken in different light will offer a clearer look into the sample tube.

No one’s expecting failure at this point, however.