Mars and Moon geology: past, present and future

One month after it landed on Mars and beamed back its first “I made it” messages, NASA’s Perseverance rover is limbering up its instruments, testing its wheels, and starting to return pictures of its new home in Jezero Crater.

“So far all is going exceedingly well,” Ken Farley, the mission’s project scientist, from California Institute of Technology, US, said this week at an online session of the 52^nd Lunar and Planetary Science Conference (LPSC). “There are no major technical issues and all instruments checked out healthy.”

Not that all of the instruments are fully deployed: that will take several more weeks. But the rover has already returned interesting data. In addition to panoramas and selfies, it has taken zoom photos of unusual rocks, including one that appears to be wind-sculpted into the shape of a harbor seal, and a larger, more distant feature that looks to be a mesa capped by an erosion-resistant layer of sandstone. 

The photos also reveal that the area around the landing zone is remarkably complex, with sand dunes to one side, and a boulder field to the other – proof that the autopilot on the rover’s descent module really did work brilliantly. 

“[It] landed us in this smooth region between two dangerous regions,” Farley says. 

Once the instruments are fully checked out and the rover is ready to move, the first goal will be to find a good spot to deploy and fly the helicopter currently tucked in its underbelly – a lightweight machine called Ingenuity which, if it works, will be the first to fly on an alien planet. 

In the interim, scientists will also be trying to figure out the rover’s initial route. It came down on the far side of a rough, dune-strewn region that lies between it and the region it really wants to explore. Driving across that region carries too much risk of getting bogged down in sand, so the rover will drive around it. But clockwise or counterclockwise? “We haven’t decided,” Farley says.

Once on the other side, however, the rover will reach its planned exploration route, designed to begin at the crater floor and eventually climb to the rim and beyond: 35 kilometres in which it will periodically stop to collect samples to cache for later retrieval for return to Earth. 

But the exploration route isn’t set in stone because who knows what alternatives might crop up as the rover begins its explorations. “This is more of a vision than a contract,” Farley says.

Meanwhile, scientists are preparing for the next stage in the sample returns from a closer world, the Moon, which NASA’s Artemis mission hopes to do in manned landings, as soon as 2024.

To prepare for this – and bridge the half-century gap between Apollo and Artemis – a program called ANGSA (Apollo Next Generation Sample Analysis) is bringing never-before-studied Apollo samples out of storage and preparing them for interrogation with modern methods.

Chip Shearer, of the University of New Mexico, one of the science heads of the program, says it’s almost like an entirely new sample-return mission – without the expense of going to the Moon to get them. And, he said at the Lunar and Planetary Science Conference, “It provides a link between the Apollo and Artemis generations of lunar explorers.” 

Some of these samples are rocks that were sealed after return to Earth and put in the deep freeze for 50 years.

Others are core samples that the Apollo astronauts painstakingly extracted from the lunar crust. The most interesting is a core sample that the astronauts immediately placed in a sealed container. ANGSA scientists hope that container has preserved trace gases that might have escaped from these rocks – gases that would have been lost in less-well-preserved lunar samples. 

“It is a testament to what you can do when you properly curate samples, long term,” says Francis McCubbin, of NASA’s Johnson Space Center, in Texas.

Opening the tube without contaminating it or losing whatever trace gases it might contain is, of course, a challenge. Timon Schild of the European Space Agency’s European Astronaut Centre, in Germany, describes it as building a high-tech can-opener.

But the process of figuring out how to do it, he says, carries important implications for future sample-return missions, including both Artemis and the samples being collected by Perseverance, portions of which might both be archived for extended periods of time, awaiting whatever advances the next 50 years might bring.

In part, he says, ANGSA will simply help us figure out how to better design the next generation of sample containers. But there are also simpler lessons, such as the realisation that it would have been nice to have made, and saved, a few duplicate sample containers so future engineers have something on which to practice.

Meanwhile, says Harrison Schmitt, one of the Apollo 17 astronauts who in December 1972 collected the soon-to-be-opened sample, “it’s great to see it happening.” 

“Of course,” he says, “we planned on this when we collected the cores.” But still, he says it’s not only exciting but rewarding “to know that those plans of the past are paying off”.