When Carl Sagan envisioned sending humans to Mars in his 1973 book “Cosmic Connections,” he asked a question that went beyond the cost and complexity of such a mission: on the red planet The possibility of life already exists, and it probably won’t be fun.
“Pathogens may exist on Mars,” he wrote. “These organisms, if transported to a terrestrial environment, could cause massive biological damage—the Martian plague.”
Michael Crichton envisioned a related scenario in his novel The Andromeda Strain.
In this case, the extraterrestrial sample contains dangerous Tagalog creatures, an example of reverse contamination, or the risk of material from other worlds endangering Earth’s biosphere.
“The possibility that this pathogen exists may be small,” Sagan wrote, “but we cannot risk even a small risk of a billion lives.”
Scientists have long considered Sagan’s warnings in mostly hypothetical fashion. But in the coming decade, they will start taking concrete action against backward pollution risks. NASA and the European Space Agency are preparing for a joint mission called Mars Sample Return. The rover on the red planet is currently collecting material that will be collected by other spacecraft and eventually returned to Earth.
No one can say for sure that this material won’t contain tiny Martians. If so, no one can say for sure that they are not harmful to Earthlings.
Given these concerns, NASA must act as if a sample from Mars could spark the next pandemic. “Because it’s not a zero percent chance, we’re doing our due diligence to make sure there’s no possibility of contamination,” said Andrea Harrington, NASA’s Mars sample curator. Handle returned samples in the same way the Centers for Disease Control and Prevention handles Ebola: Be careful.
In this case, “careful” means that once Martian samples fall to Earth, they must initially be kept in a structure called a sample reception facility. Planners for the mission say the structure should meet a standard called “Biosafety Level 4,” or BSL-4, which means it can safely house the most dangerous pathogens known to science. But it also had to be pristine: Functionally, a giant clean room would prevent terrestrial material from contaminating samples from Mars.
The agency has little time to waste: If the sample-return mission goes on schedule — and that’s certainly a big “if” — Martian rocks could land on Earth in the mid-2030s. It could take just as much time to build a facility that can safely house Martian materials, that is, if it’s built as planned and undisturbed by political or public challenges.
With no existing laboratory capable of meeting NASA’s requirements and being sufficiently clean, four scientists, including Dr. Harrington, toured some of the most dangerous facilities on Earth. She was joined by three colleagues who called themselves “NASA Tiger Team RAMA.” While the moniker sounds like the name of a military reconnaissance team, it is an acronym for the team members’ names – Richard Mattingly, NASA’s Jet Propulsion Laboratory; Andrea Harrington; Michael Calaway, a contractor at the Johnson Space Center; and Alvin Smith, also from Jet Propulsion Laboratory.
The team toured hotspots such as the National Laboratory for Emerging Infectious Diseases in Boston, the U.S. Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland, and the Centers for Disease Control and Prevention’s ominous and obscure Building 18 in Atlanta.
In total, the team visited 18 facilities that deal with bioterrorism, maintain ultra-clean rooms, or manufacture innovative devices. Members hope to figure out how existing labs work and what NASA facilities can be appropriate or optimized to keep humans safe.
For a scientist like Harrington, the rush and hurdles are worth it. “This will be the first sample return mission from another planet,” she said. The other world met humans for the first time, in other words, because humans introduced them.
Materials from around the solar system have come to Earth for study before: lunar rocks and dust from U.S., Soviet and Chinese missions; two asteroid samples collected by Japanese probes; and particles from the solar wind and comets collected by spacecraft. But Mars presents what NASA considers a “significant” risk of reverse contamination, so samples from the Red Planet fall into a legal category called “restricted Earth return.”
“We have to treat these samples as containing harmful biological material,” said Nick Benardini, NASA’s planetary protection officer. Bernardini oversees policies and programs aimed at preventing terrestrial microbes from contaminating the planets or moons in our solar system and alien material from harming Earth.
John Lammell, who served twice in the office between 1987 and 2008, believes the space agency is right to take these risks seriously, even if they are slim and seem like science fiction. “There are still a lot of unknowns about biological potential,” he said. “A place like Mars is a planet. We don’t know how it works.”
Of course, part of the Mars sample return is to figure out how the planet works — something that can’t be done properly in the field because scientists and their myriad instruments can’t travel there yet. The mission has begun. NASA’s Perseverance spacecraft, which arrives on Mars in 2021, is collecting and caching samples for future use. The samples would then be delivered to the rocket-equipped lander by the same rover or a robotic helicopter. The rocket would then launch them into Mars orbit, where a European-built spacecraft would capture the material and fly it back to Earth.
Once the spacecraft approaches this pale blue point, optimistically in 2033, the sample will fall into the desert of the vast Utah test and training site, Earth’s own Martian landscape. Scientists can then study these samples using heavy-duty instruments allowed by Earth labs.
Tiger Team RAMA’s job is to figure out how to make contamination risk an opportunity rather than a problem. Their goal is to study what existing closed and clean facilities offer, and what the space agency might need to invent.
“We want to know what’s going on in the state,” Harrington said.
To find out, the team visited seven high-containment labs in the US, one in the UK and one in Singapore, as well as ultra-clean space labs in Japan and Europe. They also visited equipment manufacturers at these facilities, as well as manufacturers of modular labs.
The biggest technical challenge is that the sample receiving facility must serve two intersecting purposes. “Earth doesn’t touch the sample,” Meyer said. That’s the goal of a pristine, clean facility: to prevent terrestrial material from contaminating Martian materials and sending false signals to scientific research.
“And the samples don’t touch the Earth,” he continued – reverse contamination. The function of the high-containment laboratory: keep the contents inside.
Cleanrooms require positive air pressure, which means the pressure inside is higher than outside. Therefore, air always flows from the inside out – from high pressure to low pressure. That’s exactly what air does, because of physics. Particles are squeezed out, but don’t force their way in.
However, high containment labs work in just the opposite way. They maintain negative air pressure, the pressure inside the walls is lower than the outside. Particles can float in, but not slip out.
NASA needs both positive pressure space to keep samples clean and negative pressure space to keep samples contained. It is difficult to integrate these conditions into the same physical space. It may require creative concentric structures and complex ventilation systems. No laboratory on Earth can reach the scale required for Mars sample return, because no laboratory ever needs to. “We’re not surprised that this doesn’t exist,” Harrington said.
The best the Tigers RAMA can do is look at how clean and enclosed facilities hold up and hopefully determine how best to combine them.
High-efficiency particulate air or HEPA filters are ubiquitous in the BSL-4 labs the team visits. The team learned about sterilization practices, such as bathing instruments in gaseous hydrogen peroxide vapor, which kills contaminants on surfaces. Efforts are still needed to find the right way to sanitize foreign substances. “In the context of these samples, research to understand decontamination is currently underway,” Harrington said.
In the end, the team presented NASA with several possibilities for what shape the Mars sampling facility could take: The agency could transform the existing BSL-4 laboratory into a more pristine state. Or, possibly requiring more money and time, the agency could build a new physical facility from Earth, designed specifically for its purpose. NASA is also considering intermediate options, such as building a cheaper modular high-protection facility and craming it into a stiffer structure.
“There’s a lot more that we’re thinking about,” Harrington said.
Regardless of NASA’s decision, the team’s investigation suggests that the process of designing and building a sample research site could take anywhere from eight to 12 years — a departure from the timeline for actual sample return. With that in mind, team members suggested that NASA has some plans around now.