When astronomer Carl Sagan wrote about sending people to Mars in his 1973 book The Cosmic Connection, he brought up a problem that went beyond the cost and difficulty of such a mission: the possibility that there was already life on Mars and that it might not be friendly.
"It is possible that there are pathogens on Mars," he wrote. "These are organisms that, if brought to Earth, could cause a Martian plague that would kill millions of people."
In his book The Andromeda Strain, Michael Crichton wrote about a similar situation. When extraterrestrial samples bring dangerous organisms with them, this is an example of "backward contamination," which is the risk that things from other worlds will hurt Earth's biosphere.
Professor Sagan wrote, "The chance that such pathogens exist is probably low, but we can't take even a low risk with a billion lives."
Since a long time ago, scientists have mostly thought of Prof. Sagan's warnings in hypothetical terms. But in the next ten years, they will start to do something about the risks of contamination from the past. The European Space Agency and NASA are getting ready for a joint mission called Mars Sample Return. A rover on Mars is currently picking up rocks and dirt that will be taken away by other spacecraft and brought back to Earth.
No one can say for sure that these samples won't have tiny Martians in them. If they do, no one knows for sure that they won't hurt people on Earth.
Nonetheless, NASA has to act as if samples from Mars could cause the next big disease outbreak. NASA's Mars sample curator, Dr. Andrea Harrington, said, "Because it's not a 0% chance, we're doing everything we can to make sure there's no chance of contamination." So, the agency plans to handle the returned samples in the same way that the Centers for Disease Control and Prevention (CDC) handles the Ebola virus: carefully.
In this case, "carefully" means that once the samples from Mars land on Earth, they must be held in a building called the sample receiving facility. Planners for the mission say that the building should meet a standard called "Biosafety Level 4" or BSL-4. This means that it can safely hold the most dangerous pathogens that scientists know of. But it also has to be clean. It has to work like a big clean room so that things from Earth don't get on the samples from Mars.
The group doesn't have much time to waste. If the mission to bring back rocks from Mars goes as planned, which is a big "if," rocks from Mars could land on Earth by the middle of the 2030s. It could take about the same amount of time to build a safe place to store the Martian materials, and that's if the building goes according to plan and isn't stopped by political or public problems.
NASA couldn't find a lab that was both clean and contained, so Dr. Harrington went on a tour of some of the most dangerous places on Earth. She worked with three other people, and they were called "Nasa Tiger Team Rama." This name sounds like the name of a military scouting party, but it is actually an acronym of the first names of the team members: Mr. Richard Mattingly, of NASA's jet propulsion laboratory; Dr. Andrea Harrington; Mr. Michael Calaway, a contractor for the Johnson Space Centre; and Dr. Alvin Smith, also of the jet propulsion laboratory.