NASA is planning its first mission to bring soil and rocks from Mars back to Earth, but before that momentous event occurs, the space agency must figure out exactly how to protect our home planet from any alien microbes that might travel.
This week, the agency will hold public meetings and seek feedback on its plan to land a spacecraft carrying Martian specimens at a US Air Force testing range in Utah in the early 2030s.
“This is perhaps the most important environmental assessment that humans have ever done,” says Peter Doran, a geologist at Louisiana State University who studies life in extreme environments.
“I think the probability that there is anything alive on the surface of Mars is very low,” says Doran, who is also part of an international committee devoted to planetary protection. “But there is a possibility.”
Having a rock sample from Mars here on Earth would allow scientists to run extensive laboratory tests to search for evidence of whether this cold, hard, rocky world was once habitable and maybe even inhabited.
For scientists, this is a long-standing dream.
Such a mission has been talked about for decades and it will cost billions of dollars to accomplish. Still, Doran says no one has figured out exactly how to handle the Martian specimens. Questions like how to contain any possible microbes? Or what specific features are needed for the laboratory (or laboratories) sure to house the rocks?
“Until recently, not much attention had been paid to the details of the sample return facility and all that,” he explains, “because we didn’t think it was going to happen.”
Now, however, the effort appears to be on a fast track, with NASA officials collaborating with the European Space Agency and making plans to launch a suite of recovery spacecraft as soon as 2027 and 2028. To prepare, the Perseverance rover NASA, which landed on Mars last year, has been drilling cylindrical rock samples and sealing them inside metal tubes.
“We have eight samples on board the rover now,” says Jim Bell, an Arizona State University planetary scientist who is part of the Perseverance rover team.
He explains that the rover has been exploring an ancient crater on Mars that appears to have once held water. Occasionally, the rover drills into a cylindrical core of rock about the size of a dry-erase marker. The core is then hermetically sealed in one of the rover’s 42 metal sample tubes.
Bell says that a long-standing joke among planetary scientists is that “the sample return from Mars has always been 10 years.” But finally, it really feels like 10 years to go, he says.
“I’m optimistic, right? We’re caching them and getting them ready to be picked up,” says Bell. “And that’s further than the planetary science community has ever gone before.”
Critics say Martian rocks carry risks
NASA officials are devising a plan to safely collect the samples: A spacecraft would land on Mars and launch a container filled with the previously collected rock samples into orbit around the planet. Once in orbit, this container could be engulfed by another container, like a big fish eating a small fish, to keep everything that has touched Mars inside.
It would then be sealed and the seal would be heat sterilized, says Brian Clement, a planetary protection expert at NASA’s Jet Propulsion Laboratory who is working on the mission.
“We’re applying very high heat. It’s going to exceed 900 degrees Fahrenheit,” he says. “We want to be able to break down any biomolecule that might have activity of interest.”
However, this is a technical challenge because scientists also want to keep rock samples cold, as they were on Mars. “I liken this to welding your metal lunch box shut while trying to keep your lunch nice and cold inside,” says Clement.
The sanitized container would then go into another container, which would also be sealed and placed in the Earth Entry Vehicle, which is what would eventually land in the Utah desert, sans parachute.
“We like to refer to it as a 90 mph fastball, where the landing spot is the glove,” says Clement. “That landing at 90 miles per hour, just like with a baseball, is well within the capabilities of the Earth entry system.”
Still, some observers find this proposal disturbing.
“We’re just going to bring it back and have it go back to the Utah desert, just like the Genesis solar sample return mission, which, of course, broke open on impact,” says Barry DiGregorio, scientist. writer with a group called the International Committee Against Mars Sample Returns, which has long opposed plans to bring Martian rocks directly to Earth.
“You can imagine what would happen if you had pathogenic organisms from another planet and you had that kind of event,” says DiGregorio.
But Clement says that multiple panels of scientific experts have weighed the risk of sample returns from Mars over the years and that “those panels have agreed that the potential danger is very, very low.”
Still, he says, NASA is taking a conservative approach. “Anything that has been in direct contact with Mars will be contained or sterilized before being returned,” says Clement.
And Bell says he’s not worried about the possibility that Martian germs mixed with the rocks could escape into the environment and cause problems or disease, “despite the fact that a lot of sci-fi fans are probably worried about that.”
Any life on Mars would not be suited to survive on Earth, says Bell, as it would have evolved in a separate biosphere, or life-supporting environment. “We’re talking about a completely different ecosystem, a completely different potential biosphere,” she says. “And of course we don’t know if there is or was a biosphere on Mars.”
In his opinion, the main danger of rupture or leakage would be contaminating the precious Martian samples with terrestrial material. That’s why the samples will likely need to be opened in high-tech facilities that can replicate the environment and atmosphere of Mars, says Bell.
Public reaction to a special delivery from Mars
While the surface of Mars is currently dry, very cold and bombarded with strong ultraviolet radiation, LSU’s Doran says it’s still possible that microbes could survive in sheltered cavities and holes or under dust.
“The chance is not zero,” Doran says, though he thinks it’s “highly unlikely.”
“We definitely have to take this position of protecting Earth, at least in the first few missions, until we know what’s out there,” he says.
One of the few efforts to find out what the public thinks about bringing home Martian rocks was carried out in the 1990s. That study found that “public perception of biological hazards associated with a Mars sample return mission it is not considered a high risk relative to other technological and environmental risks and hazards, such as nuclear technologies, food risks, and ozone depletion.”
But public perceptions may be different now, in part because of the coronavirus pandemic, says Margaret Race, one of the researchers involved in that 1990s study, who has worked on planetary protection with the SETI Institute.
“What we’re talking about is bringing it to Utah in a big desert and then you pick it up and take it to another place, a lab,” says Race, noting that people will want to know where that lab is. will be and exactly what protections will be implemented.
“I expect there will be a lot of questions,” she says.
Even with many details to be worked out, the prospect of a Martian rock being brought back to Earth is exciting for scientists like ASU’s Bell, who has studied Mars for years.
“I just want to see these things with my own eyes,” says Bell. “We’ve been looking at this world through robotic eyes for so long, and I want to see that famous red dust and I want to see the inside of some of these rocks and little grains that may have formed in a watery environment 3 or 4 billion years ago.” years”.