NASA’s first sample of Mars appears to have collapsed

Although NASA has had a string of high-profile successes on the Red Planet, Mars sometimes throws a curveball at scientists. The Perseverance rover appeared empty during its first attempt to collect a Martian rock sample last week, and NASA believes the rock likely collapsed into rubble and dust rather than remaining in one piece.

Now the rover is heading south to its next sampling target, where the team plans to try drilling again in early September.

On the first attempt, the multistep sampling process initially seemed to go smoothly. The rover pierced the red planet, closed the sample tube with a hermetic seal, and deposited the tube safely in a module in the rover’s belly on August 6. mission.

But as the team went through the data, they realized the tube was empty. In tests on Earth, some of the nuclei were smaller than others, but “we still got a sample in the tube,” says Trosper. Rocks near the next sampling site may be more similar to some they tested on Earth, hopefully improving the odds of success.

The failed sampling attempt joins several past missions that have struggled to dig through the red rocks of Mars as planned. “It’s kind of normal” when it comes to Mars missions, Trosper says. A self-hammering thermal probe on Mars’ InSight lander, for example, only managed to sink about an inch deep into the surface before popping out again.

“Once again, Mars shows us that it is not Earth,” says Trosper.

The mystery of the missing core

While Mars is now a frozen wasteland, signs of water from the past abound, from winding stream channels to sprawling river deltas. Perseverance landed on Mars in February 2021 to search for clues to ancient life in a 28-mile-wide crater that was likely once filled with a freshwater lake.

A key part of this research is collecting the first pristine samples from the surface of Mars. Equipped with 43 ultra-clean sample tubes, the Perseverance rover is expected to collect dozens of samples across the crater floor and across a former river delta. The rover would then cache the samples in an as yet undetermined location so that a future mission can retrieve them and bring them back to Earth.

The sampling process is a series of “choreographed and coordinated” events that takes a total of 11 days, says Vivian Sun of NASA’s JPL, who is co-leading the mission’s first science campaign. Scientists start by abrading part of the surface, which removes any dust or coating and allows them to study the composition of the underlying rock.

The final leg of Perseverance’s first sampling attempt began on the evening of August 5, after the team gave orders for the automated process to begin. They woke up the next morning at 2 a.m. to check on Perseverance’s progress, finding that he had successfully pierced the surface. One image showed exactly what they expected: a hole surrounded by a ring of sand known as tailings. “It was beautiful,” says Trosper.

At around 8:30 a.m., the team received images of a successfully sealed tube inside the rover. But then they looked at the rest of the data.

Before the tube was sealed, an arm inside the rover pushed it up into a sensor to measure the volume of material, revealing nothing inside. The team then uploaded images by looking into the tube to confirm it was empty.

“We started racking our brains,” Trosper says.

Over the next two days, the team set to work to determine what was wrong. Snapshots scanning the sample hole revealed a suspicious pile of dust at the bottom. Measurements of the hole depth and images of the surrounding area further suggested that the rover didn’t just drop the small cylinder of rock. The drill, it seems, instead shattered the surprisingly friable rock.

“The hardware worked as ordered, but the rock didn’t cooperate this time around,” wrote Louise Jandura, NASA chief engineer for Perseverance sampling and caching, in a mission blog post.

The uncooperative rocks of Mars

This is not the first time that Martian rocks have not acted as scientists expected. NASA’s Phoenix lander, which landed on Mars in 2008, initially struggled to pick up the planet’s rusty red regolith in a device that heats rocks to sniff their components. The material was “stickier” than expected and the stones did not fall easily from the shovel. Scientists are still debating why, Trosper says.

Another issue was with the self-hammering thermal probe, or “mole,” on NASA’s InSight lander, which is currently studying the interior of Mars. Every time the mole tried to sink in, it come out again. NASA finally gave up in January 2021 after several pounding attempts, citing a lack of friction that prevented the probe from penetrating more than an inch underground.

In the months of preparation leading up to the launch of Perseverance, the team took more than a hundred training samples on Earth to try and make sure the process went as planned. But when designing missions to other worlds such as Mars, Trosper says scientists often talk about “unknown strangers,” situations where something totally unexpected happens. The basic sample is just that.

Such surprises are an opportunity to discover something new. “One of the beauties of the work we do,” says Trosper, “is making some of these” unknown unknowns “known.”