In Michael Crichton's 1969 novel The Andromeda Strain, a deadly alien microbe hitches a ride to Earth aboard a downed military satellite and scientists must race to contain it. While fictional, the plot explores a very real and longstanding concern shared by NASA and world governments: that spacefaring humans, or our robotic emissaries, may unwittingly contaminate Earth with extraterrestrial life or else biologically pollute other planets we visit. It's an old fear that's taken on a new relevance in the era of COVID-19, said Scott Hubbard, an adjunct professor of aeronautics and astronautics at Stanford University. "I have heard from some colleagues in the human spaceflight area that they can see how, in the current environment, the general public could become more concerned about bringing back some alien microbe, virus or contamination," said Hubbard, who is also the former director of NASA Ames and the first Mars program director. Hubbard is a co-author of a new report published last month by the National Academies of Sciences, Engineering and Medicine that reviews recent findings and recommendations related to "planetary protection" or "planetary quarantine" -- the safeguarding of Earth and other worlds from biological cross-contamination.

It may sound like a plot from a science fiction film, but NASA and the world governments are concerned about alien viruses contaminating Earth. As the first humans prepare for the Mars mission, experts warn that protocols are necessary to keep extraterrestrial pollutants from hitchhiking on space ships and astronauts when returning home from the Red Planet. Stanford professor of aeronautics and astronautics Scott Hubbard said in an interview that the solution is'planetary protection'. Mechanical systems will have to undergo a combination of chemical cleaning and heat sterilization, while the tubes containing samples from Mars need to be treated'as though they are the Ebola virus until proven safe.' Hubbard also suggests that astronauts must be quarantine once they touch down on our planet, as the first men who visited the moon in the Apollo mission did. As the first humans prepare for the Mars mission, experts warn that protocols need to be created to keep extraterrestrial pollutants from hitchhiking on space ships and astronauts when returning home.

In the summer of 1957, the Earth stood witness as a meteorite cratered in rural Pennsylvania, bringing with it a people-eating plague never seen: an alien amoeba with the taste for human flesh. While we had Steve McQueen around for the first invasion, humanity is now defended against microbial marauders from outer space by NASA and its international counterparts. Biological contamination goes both ways, mind you. Just as important as keeping extraterrestrial organisms from reaching the surface (aka "backward contamination") is ensuring that our planetary probes carry as few microbial hitchhikers from Earth as possible ("forward contamination"). To that end, in 1958, the U.S. National Academy of Sciences (NAS) issued a decree urging "that scientists plan lunar and planetary studies with great care and deep concern so that initial operations do not compromise and make impossible forever after critical scientific experiments."