How Big of a Problem Is Space Contamination?

This question originally appeared on Quora.

Answer by Robert Walker, writer of articles on Mars and space:

For me, the No. 1 issue that is rarely discussed is contamination of the solar system by Earth microbes and of Earth by samples returned from space. It is not so much that the issues are not discussed at all. There are many papers and workshop reports about them. The problem is that they are rarely discussed by the public and are ignored in news reports. So there is hardly any public awareness of these issues.

The planetary protection officer Cassie Conley goes to schools to talk about these issues to spread awareness, and other things are done to try to help spread awareness. All the reports say this, often asking the question: What can we do by way of outreach to get more public discussion of these issues?

I think journalists can help by covering these issues and not just report human missions to the solar system as if they had no planetary protection issues. I also think many people don’t know that Mars, for instance, is listed as a planet that needs to be protected from Earth microbes in the planetary protection guidelines. It is one of the top three targets that need to be protected, including Europa and Enceladus. That’s the direction of “forward contamination.”

Then, in the other direction, the Earth itself needs to be protected. You may remember the way that the astronauts and lunar samples from the moon were quarantined on return to Earth. Those measures were soon dropped, as we realized that the moon almost certainly has no present-day life at all. But the precautions we took were so inadequate that if there had been life on the moon able to infect our oceans, Earth would have been infected right away, as soon as the astronauts splashed down from Apollo 11. They simply opened the hatches  and took the astronauts to the waiting ship in an open boat at sea. Although the astronauts had decontamination suits on, no effort was taken to stop the air and dust in the cabin from spreading out over the sea. You can see it here. Hopefully we can do better than that with Mars.

It may seem like science fiction, but so did mobile phones a few years ago. We are seriously considering returning samples from another planet  to Earth, and there is a possibility that these samples could contain alien life. Not alien as in Alien the movie. But alien as in they may have novel biochemistry not related to Earth life at all or branched off before our earliest known ancestor or has been separated from Earth for millions or billions of years. They may have evolved new traits.

The U.S. and Europe both have made detailed studies to find out whether and how we can receive any Mars samples safely, and both came to the conclusion that we need to build a specially designed receiving facility. Nobody has ever built a facility like this before. It goes way beyond anything required of any normal biohazard laboratories, and estimates for its cost—including the design—run into hundreds of millions of dollars. If we plan to receive samples some time in the early 2020s, we should have already started work on its detailed design or should start on it very soon, because it needs to be operational for some years so the staff get used to procedures before samples are returned. It seems a clumsy, costly way to ensure protection of the Earth from a tiny half-kilogram box of samples from Mars. But that is what the studies recommended. The U.S. went so far as to commission design studies for the facility, such as this one for an enclosed facility fully automated with telerobotics to make sure that there is no connection at all between the outside world and the interior.

Their studies concluded that it would need to be a new type of building, as it has to both protect the samples from Earth life and the Earth life from the samples. What’s more, the samples have to be contained at a sub-microscopic level—there may be hazardous particles that are about an order of magnitude too small to be seen with our best optical microscopes, which must not be released into the Earth environment. They recommended that it is designed around a probability of release of a 10 nm particle of less than 1 in a million. The smallest particles we can see with an optical microscope are 200 nm with “diffraction limited” observation.

I think we are doing this back to front, and we need to find out what is there before we return to Earth—study it in situ with instruments we now have that they didn’t have for Apollo. Then depending what we find, we will only return it with extreme caution. If it is larger DNA-based life, which we have already sequenced and know a lot about before we return it, then we may not need to take so many precautions. And if we don’t find life or are pretty sure there is no life there at all, that’s a different situation. Our modern instruments can detect a single amino acid and the most subtle signatures of life. So, with present-day technology, it’s totally feasible to do it this way around. Indeed, that is the plan for ExoMars.

But in any case, the public has to be involved. Scientists are proposing taking a risk here, and their plans are not 100 percent reliable. It’s a tiny probability of escape—and even less likely that whatever escapes is harmful. But how reliable is that probability assessment first? What about design errors? Most of our spacecraft designs have flaws in them at one point or another, so what if there is a flaw in this design also? What about human error? Impatient researchers taking the sample out at an early stage because they are so keen to do the science or accidents taking it to the facility? The official reports do not take this into account; they mention these issues but don’t try to assess them, as it is not their “design brief.” Should we take a 1 in 1 million or a 1 in 1 billion or even a 1 in 1 trillion chance with something that in worst case could impact billions of human lives?  

Carl Woese, who first classified the Archaea said in an interview:

When the entire biosphere hangs in the balance, it is adventuristic to the extreme to bring Martian life here. Sure, there is a chance it would do no harm; but that is not the point. Unless you can rule out the chance that it might do harm, you should not embark on such a course.

Carl Sagan thought that we should not take such a risk. He said that he’d want to be really sure that the plans would work and contain the sample before considering returning a sample to Earth. Sagan wrote in his book Cosmic Connection:

Precisely because Mars is an environment of great potential biological interest, it is possible that on Mars there are pathogens, organisms which, if transported to the terrestrial environment, might do enormous biological damage — a Martian plague, the twist in the plot of H. G. Wells’ War of the Worlds, but in reverse. This is an extremely grave point. On the one hand, we can argue that Martian organisms cannot cause any serious problems to terrestrial organisms, because there has been no biological contact for 4.5 billion years between Martian and terrestrial organisms. On the other hand, we can argue equally well that terrestrial organisms have evolved no defenses against potential Martian pathogens, precisely because there has been no such contact for 4.5 billion years. The chance of such an infection may be very small, but the hazards, if it occurs, are certainly very high. …

The likelihood that such pathogens exist is probably small, but we cannot take even a small risk with a billion lives.

This is a decision we can’t leave to scientists. They are keen to make new scientific discoveries, and to them, if they can show that there is a far less than a 1 in 1 million chance of something happening to humanity as a result, then it is well worth the almost infinitesimal risk to make the biggest scientific discovery of the last century, or so they think.

But the general public might not agree here. They might feel, like Carl Sagan, that: “The likelihood that such pathogens exist is probably small, but we cannot take even a small risk with a billion lives.” And there are many different views on all this. There are biologists who say that we don’t need to return a sample at all at this stage, which then at least puts off the question until we find out more. Whatever we finally decide, this has to be decided in full and open public debate.

The official reports stress the need for public debate:

Considering the global nature of the issue, consequences resulting from an unintended release could be borne by a larger set of countries than those involved in the programme.

It is recommended that mechanisms dedicated to ethical and social issues of the risks and benefits raised by an MSR are set up at the international level and are open to representatives of all countries.

The theologian Richard Randolph put this especially strongly in his study:

… the problem of risk — even extremely low risk — is exacerbated because the consequences of back contamination could be quite severe Without being overly dramatic, the consequences might well include the extinction of species and the destruction of whole ecosystems. Humans could also be threatened with death or a significant decrease in life prospects.

In this situation, what is an ethically acceptable level of risk, even if it is quite low? This is not a technical question for scientists and engineers. Rather, it is a moral question concerning risk. Currently, the vast majority of the people exposed to this risk do not have a voice or a vote in the decision to accept it. Most of the literature, on back contamination is framed as a discourse among experts in planetary protection. Yet, as I’ve already argued, space exploration is inescapably a social endeavor done on behalf of the human race. Astronauts and all the supporting engineers and scientists work as representatives of the human race …

In this situation, to treat  persons with dignity and justice means that everyone must have an opportunity to voice their opinion concerning whether humans should accept the risk …

Nobody is trying to hide anything here, I’m sure. It just doesn’t “grab the news” and is the less interesting kind of aspect of space exploration. I’m not sure what we can do. It is not the sort of thing that hits the news. But I think it doesn’t help that none of the news stories even mention this need for a full debate about whether they should do this at all and whether it is worth doing.

The same is also true for the forward contamination issues. This should be mentioned in all the news stories about human colonization of Mars. It needs to be explained that nobody has yet worked out a method for human exploration of Mars that is consistent with the needs for planetary protection. That should be common knowledge for everyone who knows about the subject. But instead, almost nobody realizes this. I don’t blame the journalists particularly—they are fed press releases and they don’t mention it. And NASA doesn’t talk about it—almost nobody does. Just a few such as the planetary protection officers, on the few occasions they are interviewed and hit the news. If anyone talks about sending astronauts to Mars, he or she should be asked, What are your plans for protecting Mars from contamination by Earth microbes? so we can get a chance to look at the plans as soon as possible.

If there’s talk about returning a sample to Earth, then we should be asking: How do you intend to protect the Earth? What is your target probability for contaminating the Earth, and how confident are you that it can be achieved? What is the worst-case scenario, and do you have any estimated probabilities for that? It is our decision, not a decision forscientists. In the final analysis, they are exploring space for us—and answer back to us.

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