In a press conference on Friday, NASA revealed more about the Perseverance rover’s first successful collection of Martian rock, which was confirmed Monday. The successful sampling is the fundamental first step in a 10-year-plan to bring Martian rock to Earth for close examination.
A surprise from the conference was that, since that first collection, Perseverance actually collected a second sample core from the same rock. NASA scientists said that the rock was so nice (meaning scientifically intriguing) that they cored it twice. The hope is that samples like these will make it to Earth by the 2030s, in one of the most ambitious experiments humans have conducted in space, and will offer insights into Martian geologic history and the tantalising possibility of ancient Martian life.
“I’m happy to say that not one, but that the first two samples of another planet are prepped and stowed as the first official candidate samples to be returned to Earth by a future mission,” said Lori Glaze, director of NASA’s Planetary Science Division. “One of the reasons we explored Mars is because it holds a rock record that’s been untouched for about 3.5 to 4 billion years … Mars doesn’t have plate tectonics, so its early history is well preserved in the layers of rocks on the planet’s surface.”
The first attempt to sample rock was unsuccessful, as previously reported by Gizmodo. Though early indications suggested that a rock sample had been taken, later analysis revealed there was no sample in the tube. NASA suspects the failure was due to the frailty of the target rock, which appears to have crumbled during the coring process.
NASA’s next target was a rock to the west in Jezero Crater, where Perseverance landed in February and is the site of an ancient lake, long since dried up. On the west side of Jezero is a river delta, which scientists believe is the most intriguing location to search for biosignatures — evidence of life — likely in the form of fossilized microbial mats, similar to the primordial life on Earth.
Perseverance’s science mission has the rover meandering westward toward the delta, picking up rock samples as it goes. The drilling process is thus: Perseverance’s robotic arm has a coring drill on its end, which is placed on the rock target. The rock’s surface is abraded to get rid of any crud that has accumulated. As the rock is drilled, it is extracted and placed in a narrow white sample tube.
The arm then pulls the filled sample tube into the rover’s body, which has a sampling processing centre. There, the sample is imaged, measured, sealed, and stored. And all this is happening 246 million miles away from the human controllers.
“We all take significant pride in continuing to do things that are hard and challenge ourselves, but we know, and as demonstrated by what we’ve just done, that continuing to work as a team we really can achieve these amazing accomplishments,” said Jessica Samuels, Perseverance’s surface mission manager, during the press conference.
The first, failed sample site is called Roubion and is located on a flat Martian paving stone. The second and third sites were on a more robust rock on the nearby Artuby ridge. That rock is called Rochette, and its core sites are named Montdenier and Montagnac. NASA scientists said that Roubion may be visited later and tried again, as it is still a site of great scientific interest.
Katie Stack Morgan, Perseverance’s deputy project scientist, said that, based on current observations, the team tentatively believes both the paving stone and Rochette originated in ancient lava flows. (This determination comes on the heels of much debate as to whether Jezero’s rock is sedimentary or igneous/volcanic.) They determined this based on both the visible textures of both rocks and finer-scale textures.
“They show signs of sustained interactions with groundwater,” Stack Morgan said. “If these rocks experienced water for long amounts of time, there may be habitable niches within these rocks that could have supported ancient microbial life.”
Spectral analysis of the rock cores using different instruments aboard the rover, including the PIXL instrument, identified calcium, sulphur, and small inclusions of salt in the rock.
“We have collected a rock from the floor of the Jezero Crater that is igneous, or volcanic, in origin, and it has salts within it. The presence of salts indicate that the rock was subject to water. The water percolated through the rock and, as it percolated and evaporated afterwards, it left behind this salty residue,” said Yulia Goreva, the Perseverance return sample investigation scientist.
Back on Earth, such a sample would be analysed to determine its exact mineralogical composition, its age, and its chemistry. Tiny inclusions in the salt would reveal something of what Jezero Crater was like when it was covered in water, Goreva added.
It’s a huge, metaphorical sigh of relief that Perseverance is able to core the rock at all. The Martian surface behaves in unexpected ways, as the InSight Mars lander team found out when their “mole” digger got hopelessly stuck in the dusty surface and had to be abandoned.
Once the samples get to Earth, they will be handled carefully to make sure they last. It’s not every day that you get the funding and human power to bring rocks from a distant world to our planet. It also marks a precursor to NASA’s long game: getting humans on Mars, so that we don’t have to do this whole robotic rigamarole forever.