When Carl Sagan imagined sending humans to Mars in his book The Cosmic Connection, published in 1973, he mentioned a problem beyond the cost and complexity of such a mission: the possibility that life already existed on Earth. red planet and that maybe things didn’t work out too well.
“It is possible that on Mars there are pathogens,” he wrote, “organisms that, if transported to the terrestrial environment, can cause enormous biological damage — a Martian plague.”
Michael Crichton imagined a similar scenario in his novel “The Andromeda Enigma”.
Such situations, where extraterrestrial samples contain dangerous hitchhiking organisms, are examples of reverse contamination, or the risk of material from other worlds harming Earth’s biosphere.
“The probability that these pathogens exist is probably small,” Sagan wrote, “but we cannot take even a small risk with a billion lives.”
Scientists have long viewed Sagan’s warnings generally in hypothetical terms. But over the next decade they will begin to act concretely on the risks of reverse contamination. NASA and the European Space Agency (ESA) are preparing for a shared mission called Mars Sample Return. A probe on the red planet is now excavating material that will be collected by other spacecraft and later brought to Earth.
No one can say for sure that this material will not contain small Martians. In that case, no one can say with certainty that they will not be harmful to Earthlings.
With these concerns in mind, NASA must act as if samples from Mars could spawn the next pandemic. “As it is not a zero percent chance, we are doing our due diligence to ensure there is no possibility of contamination,” said Andrea Harrington, curator of Mars samples at the US space agency. So NASA plans to handle the samples brought in the same way the Centers for Disease Control and Prevention handles Ebola: carefully.
“Carefully” in this case means that once samples from Mars arrive at Earth, they must initially be kept in a structure called the Sample Reception Facility. Mission planners say the structure must meet a standard known as “Biosafety Level 4,” or BSL-4, meaning it is capable of safely containing the most dangerous pathogens known to science. But it also needs to be immaculate: functionally, a giant cleanroom that prevents substances from Earth from contaminating samples from Mars.
The agency has little time to lose: if the sample return mission happens on time — admittedly a big “if” — rocks from Mars could land on Earth in the mid-2030s. facility that can safely contain the Martian materials, and that if it is built on schedule, without disruptions from political or public problems.
As no existing laboratory was airtight and clean enough for NASA, four scientists, including Dr. Harrington, toured some of the most dangerous facilities on the planet. She was accompanied by three colleagues, who called themselves “Nasa Tiger Team RAMA”. Although this moniker sounds like the name of a military patrol group, it is an acronym for the first names of the team members –Richard Mattingly of NASA’s Jet Propulsion Laboratory; Andrea Harrington; Michael Calaway, contractor for the Johnson Space Center; and Alvin Smith, also of the Jet Propulsion Laboratory.
The group visited landmarks such as the National Emerging Infectious Disease Laboratories in Boston, the U.S. Army Infectious Disease Medical Research Institute in Fort Detrick, Maryland, and the menacing Building 18 of the Centers for Disease Control and Prevention. , in Atlanta.
In total, the team visited 18 facilities that deal with biological horrors, maintain ultra-clean rooms or manufacture innovative equipment for any purpose. Members hoped to find out what worked in existing labs and what a NASA facility could utilize or optimize to keep humanity safe.
For scientists like Harrington, the rush and the hurdles are worth it. “This will be the first sample return mission from another planet,” she said. The first time another world meets humans, in other words, because humans introduced them.
Materials from across the solar system have reached Earth before for study: lunar rocks and dust from American, Soviet and Chinese missions; samples of two asteroids collected by Japanese probes; and particles from the solar wind and a comet collected by spacecraft. But Mars presents what NASA considers a “significant” risk of reverse contamination, so samples from the red planet fall under a legal category called “Restricted Return to Earth.”
“We have to treat these samples as if they contain hazardous biological materials,” said Nick Benardini, NASA’s planetary protection officer. Benardini oversees policies and programs that try to prevent Earth microbes from contaminating planets or moons in our solar system and extraterrestrial material from harming Earth.
John Rummel, who worked at the office in two stages between 1987 and 2008, thinks it’s okay for the space agency to take the risks seriously, even if they are small and seem like science fiction. “There are significant unknowns regarding the biological potential,” he said. “A place like Mars is a planet. We don’t know how it works.”
Part of the purpose of Mars Sample Return is to find out how the planet works, of course — something that can’t be done properly on-site because scientists and their myriad instruments can’t travel there yet. The mission has already begun. NASA’s Perseverance spacecraft, which arrived at Mars in 2021, is collecting and storing samples for future collections. The samples will then be transported by the same rover or a robotic helicopter to a rocket lander. The rocket will then launch them into orbit around Mars, where a spacecraft built on Europa will pick up the material and bring it back to Earth.
As the spacecraft approaches that pale blue point, with optimism in 2033, the samples will fall into the desert of Utah’s sprawling Test and Training Range, a true Martian landscape on Earth. Then scientists will be able to study the samples with the heavy instrumentation that Earth’s laboratories allow.
Tiger Team RAMA’s job was to figure out how to make the risk of contamination more of an opportunity than a problem. Its purpose was to research what existing high containment (airtight) and clean facilities offered and what the space agency might have to invent.
“We wanted to understand what the state of the state was,” Harrington said.
To find out, the team visited seven high containment labs in the United States, one in Britain and one in Singapore, as well as super-clean space labs in Japan and Europe. They also visited equipment factories at these facilities and at modular labs.
The biggest technological challenge is that the Sample Receiving Unit must serve two cross purposes. “Earth doesn’t touch the sample,” Meyer said. That’s the goal of an immaculate and clean facility: to prevent substances from Earth from contaminating Martian materials and giving false signals to scientific studies.
“And the samples don’t touch Earth,” he continued—reverse contamination. The function of a high containment laboratory: to keep what is inside isolated.
Cleanrooms require positive air pressure, which means that the pressure inside is higher than the outside. Air always flows, then, from the inside to the outside—from the highest pressure to the lowest pressure. It’s simply what air does, because of physics. Particles are forced out, but not in.
High containment labs, however, work the opposite way. They maintain negative air pressure, with less pressure inside their walls than outside. Particles can enter but cannot leave.
NASA needs 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 sophisticated ventilation systems. No laboratory on Earth has done this on the scale that the Mars Sample Return requires, because no laboratory has ever needed it. “We’re not surprised it doesn’t exist,” Harrington said.
The best Tiger Team RAMA could do was see how the clean and contained facilities held up and hope to determine the best way to combine them.
Within the BSL-4 labs the team visited, high-efficiency particulate air, or HEPA, filters were ubiquitous. The team learned about sterilization practices, such as bathing instruments in gaseous vapors of hydrogen peroxide, which kill surface contaminants. Work still needs to be done to find the correct way to sterilize the alien material. “Research to understand decontamination, in the context of these samples, is ongoing,” said Harrington.
In the end, the team presented NASA with some possibilities for what a Martian sample facility could look like: The agency could alter an existing BSL-4 lab to be purer. Or, likely requiring more money and time, the agency could build a new facility designed solely for its purposes. NASA is also considering intermediate options, such as building a cheaper high-containment modular facility and placing it inside a harder-shelled building.
“There’s still a lot on the table that we’re looking at,” Harrington said.
Whatever NASA’s decision, the team’s investigation suggested that the process of designing and building a sample study site could take anywhere from 8 to 12 years — contrary to the timeline of the actual sample return. In light of this, team members recommended that NASA produce certain plans now.
Translated by Luiz Roberto M. Gonçalves
