How do we make sure we don’t bring harmful extraterrestrial microorganisms back to Earth from space? How do we keep our Earth microbes from contaminating potentially habitable worlds like Mars or Europa? How much effort do we really need to put into protecting these hypothetical lifeforms?
SETI marine biologist Margaret Race joins us to explain how NASA approaches these planetary protection problems. Philosopher Kelly Smith explores the ethical questions about the moral value of extraterrestrial life. And theologian Michael Waltemathe presents a religious perspective on planetary protection.
The transcript for this episode is below.
Imagine this: Your space settlement wants to expand into a new region of the surface. But the surveyors have just reported back, and there’s a problem. They’ve discovered evidence of microbial life in an underground pool near where you want to build. The biologists are already arguing with each other about whether this is truly extraterrestrial life, or just some invasive Earth bacteria brought here by the settlers. But the engineers are pointing out that the power plant you were planning to build in the new area will almost certainly be harmful to this tiny ecosystem. What do you do?
Welcome to Making New Worlds, a podcast about the ethical issues involved with settling space. I’m Erika Nesvold. Today’s episode is about the possibility of extraterrestrial life. Specifically, the kind of non-intelligent, microbial life that scientists speculate might exist in certain places in the Solar System, including Mars. We don’t know whether this life exists, or even what it would look like, but we have to consider the possibility that this hypothetical life might pose a threat to life on Earth, or vice versa.
This issue is called planetary protection, which refers to both protecting the planet Earth from contamination by extraterrestrial life, and protecting other planets from contamination by Earth life. Planetary protection is not a new idea. In fact, it’s covered in Article IX of the Outer Space Treaty of 1967, which requires that the exploration of space avoids both the “harmful contamination” of the Moon and other celestial bodies, and any “adverse changes in the environment of the Earth” due extraterrestrial material. NASA has an Office of Planetary Protection that maintains policies to ensure that missions don’t violate this part of the treaty and other planetary protection regulations.
This is one of our more science-y topics, so I called up a scientist friend of mine and an expert in planetary protection to walk us through some of the challenges.
Margaret Race: “My name is Margaret Race, and I’m a marine biologist and ecologist who works with SETI Institute. And I am a contractor with NASA who asks questions about planetary protection.”
Margaret got into the planetary protection business on the back contamination side of the problem — the question of how to prevent extraterrestrial microbes from getting loose on Earth. She was studying invasive species on Earth at a time when NASA was really starting to think about how to prevent bringing back invasive species from space.
Margaret Race: “So I got a call from someone at NASA who said, would I come to a workshop? They were beginning to talk about sample return– now this is, mind you, in the early 1990s– and said we want to think about how we would include questions of risk with sample return and environmental impact statements. How would you build the lab to take samples from Mars back to Earth? And how do you tell people in an environmental impact statement that, “Don’t worry, we can handle it”? So these are questions that any federal government agency has to think about when you’re proposing to spend money on a new technology, new siting of something.”
Even though they were planning for it back in the 90s, we still haven’t done a sample return from Mars yet. But we have brought back samples from another celestial body: the Moon. In fact, we even sent and brought back people. The Apollo program put a lot of effort into preventing back contamination.
Margaret Race: “We know that when the astronauts went on the Apollo missions, there was quarantine. We did contain things. Materials were handled in glove boxes in order to make sure that we didn’t inadvertently introduce something to Earth. However, that was back in the late 60s, early 70s when we were designing this. And I tell students, if we– If there were life on the Moon, we would have it here. We didn’t know about the microbiome and how many microbes are associated with humans. Our view at the time was really that, you know, germs cause disease. And we didn’t have this same, larger view of, you know, biogeochemical cycles and things like that. So when NASA and the international community began talking about bringing back samples from Mars in robotic spacecraft and/or bringing back humans from Mars, they took that protocol and quarantine specifications that were done in Apollo and really looked at them carefully and said, “How would we go forward from here?””
So now that NASA is starting to talk about sample return from Mars again, and now that lots of different groups are talking about sending humans to Mars, people are taking a fresh look at our backwards contamination protocols and technologies. And not just for NASA — for everyone who wants to bring material or people back to the Earth from space.
Margaret Race: “And so right now, the international community is saying, “Let’s take a look at sample return again. And so they– This spring, there’s a meeting in Germany, looking at European sample returns. And also, the U.S. is looking at it as well. And each one of them has to be done to protect the science and the astrobiology questions. But also it has to be done in accordance with the science requirements and legal policies and laws of the country where it’s placed. So if we have a sample return facility in the U.S., it would have to follow U.S. law. And likewise, if a commercial group was coming back and we hadn’t found out about Mars yet, the commercial group would also be subject to the same kind of restrictions. Doesn’t matter that you’re bringing something back– If you’re coming in from a vacation in South America and they stop you and ask, “Have you been on a farm? Do you have any fruits or vegetables?” They also stop container loads of things coming in, as well. So it doesn’t matter whether you’re commercial or not. The law still holds. So for thinking about humans to Mars, we’re now looking at, okay, how would you do that? And what are the big research questions we still have to address? So this is happening very much, now.””
You don’t even have to read or watch science fiction to understand the risks of backwards contamination. Just look at the problems we have on Earth with communicable diseases or even just invasive species. Quarantines and customs checks for people visiting the Earth from a space settlement might just become a part of the routine, just like it is for international travelers on Earth today.
But then there’s the other half of planetary protection: forward contamination, what the Outer Space Treaty calls “harmful contamination” of the Moon or other bodies. Again, this idea is decades old, and some of the earliest concerns were about scientific integrity.
Margaret Race: “Surprisingly, in the– at the time of Sputnik, so this is back in the 19– late 1950s, a group of biologists were already saying, if we can send spacecraft out there to the Moon and beyond to look for life, we don’t want to spend all this– these millions and millions of dollars, now billions, and get up there and discover life but find that it was launched with our spacecraft from Earth.”
Let’s say we send a few missions to Mars. Suddenly one of the missions comes back with exciting news: they’ve discovered extraterrestrial life in the form of tiny microbes living on the polar ice caps on Mars. But if humans have been bouncing around the surface of Mars for a few years, how can we be sure that we didn’t bring that life with us? Sure, maybe these new microbes will look significantly different than Earth life, but what if it’s been decades since humans first set foot on Mars? What if those first Earth microbes have just evolved to thrive in their new environment?
Or maybe it’ll be really obvious that this Martian life couldn’t have evolved from Earth life. Maybe it will have a completely different DNA structure, or won’t have DNA at all. There’s still the possibility that our presence on Mars could harm these microbes, even wipe them out. After all, we’re pretty good at causing species to die out on Earth without even trying. And Mars is already a harsh environment. If we show up on Mars with our industrial-strength cleaners and nuclear power plants and Earth viruses, we might kill off the local life before we even get the chance to study it.
Kelly Smith: “If you’re saying, well, the goal is to preserve, say, microorganisms, so that we can study those microorganisms, then to some extent, there’s a scientific fix for this problem.”
That’s Kelly Smith, a philosopher at Clemson University. He studies social and conceptual issues surrounding astrobiology.
Kelly Smith: “The question would be something like, how diverse are the microbes that are going to be endangered, you know? Maybe you shouldn’t locate your human settlement in a particularly delicate, rich ecosystem because you’re going to be destroying microbes that will never be seen again. If there’s a particular species of microbe which is ubiquitous on Mars, it’s everywhere, then there’s less of a concern in the same way that there’s less of a concern on Earth if building a settlement chases off several field mice. We don’t really spend a whole lot of time worried about that, whereas snail darters or some exotic species of zebra or something like that, that’s much more concerning.”
Kelly pointed out that some of the most interesting areas of the forward contamination issue involve conflicts between scientific interests.
Kelly Smith: “Let’s suppose that there’s a warm, salty ocean underneath the ice cap on Europa. And we have reason to suspect that there’s life down there, like we’ve sampled some of the steam coming off the vents, and there are cells! And so we think, “Oh my gosh! There could be a really complicated ecosystem with fish and maybe even mammals and stuff down there.” But there’s absolutely no way you can put a probe down into the Europan ocean without contaminating it. It’s just not possible. So if the point of preserving life is to preserve the science, but you can’t do the science at all without taking some risk, now you’ve got a real quandary, even if everybody agrees it’s all about the science, you’re gonna have scientists arguing with each other. And that, I think is where things get more interesting.”
But let’s set the question of science aside for a moment. Is it really okay for us to invade another planet and start remodeling the place if it means potentially killing the local lifeforms?
Kelly Smith: “So you might be concerned with life on Mars for its own sake, irrespective of what science you might do on it. If you’re concerned about life on Mars irrespective of the science, then in some sense it doesn’t matter how diverse the microbes are that you’re destroying or not inconveniencing by your settlement. It might be unethical have a settlement on Mars at all.”
So if we take this argument to its extreme, it means we should never go anywhere that might potentially harbor life, for fear of harming that life. On the other hand, remember that we’re talking about microorganisms here, at least for Mars.
Kelly Smith: “Although in principle, that argument makes a lot of sense, I think I and a lot of other ethicists would say, “Uh, you’re talking about microbes, that’s a difficult argument to make.” Because you have to first grant that microbes, as a class of organisms, are somehow on the same level with human beings and that’s– I’m not saying you can’t make an argument to that effect, but it really stretches credulity. So it’s an uphill battle.”
I asked Kelly if this means that the argument might be a little different if we discovered more complex life in space, not necessarily intelligent life, but maybe something a little bigger than a microbe.
Kelly Smith: “I think almost everybody, including professional ethicists, but also just your average guy on the street, if you say, “Gosh, doing this mission is going to kill five billion really common Martian microbes,” people will yawn. But if you said, “Well there’s Martian bunnies, and we’re gonna kill a whole bunch of them,” then people are gonna get very upset. You know, when I was in graduate school, one of the most important things I learned is the fundamental distinction in biology between warm fuzzies and cold pricklies. You can do whatever you want to to a cold prickly and people just don’t care. You can take a sea urchin and inject it with potassium chloride and watch it go into spasms and everyone thinks it’s just interesting. But if you did that to a bunny rabbit, people would freak out. And so that’s just an intuitive reaction, but I think that even most professional ethicists would say you can give a legitimate justification for that. Maybe not quite the way people cash it out intuitively, but it’s not silly to think that, for example, more complex, social organisms have a higher moral value that a microbe… People, for example, have probably way too much emphasis on human value and on mammalian values, because those are like us. But nevertheless, multicellular versus single cellular, that’s not too hard to defend.”
The story is also different if you’re talking about the extinction of an entire species, instead of just a small portion of the population of microbes on the planet.
Kelly Smith: “All the Martian microbes are all representatives of particular species of microbe? Then what you’re really talking about is not microbes, but a species or a microbial ecosystem. And that clearly ups the ante. Though again, how much is a bit unclear.”
When I asked marine biologist Margaret Race about whether we had the right to harm extraterrestrial life in the pursuit of space exploration and settlement, she said this question goes way beyond the legal and scientific questions that she works on.
Margaret Race: “So the Outer Space Treaty, the way it was written, and the Section IX– Article IX, which talks about avoiding harmful contamination– When you really look at it, the lawyers look at it in recent years and said actually, what it focuses on is avoiding harmful contamination that would affect your science. And then they said, “Hm, that doesn’t have anything to do with protecting Mars, for instance, or protecting other bodies that you’ve gone to. What are our obligations there? And what if we find life out there?” So you have touched on things that go even beyond the science, beyond the law and the policy and touch on legal and– I mean, ethical and philosophical, and I would even say theological, questions. If you find microbes on Mars, and they are different and we can just show that scientifically, they’re different than anything we know of on Earth, and they don’t maybe have DNA or they don’t map on our tree of life that taxonomists and biologists have worked out, does that make them a second Genesis? That’s not a science question. Scientifically and otherwise, a discovery of life someplace else would be amazing. Highly significant. But, if that– you want to talk about meaning, I can give you the astrobiological and science meaning and I also am interested in how that plays over the policy. But you would need an ethicist or a theologian to talk about what it means to a Buddhist, or what it means to a Muslim, or a Christian of some sort. Or to an atheist.”
So let’s get a theologian’s perspective on planetary protection!
Michael Waltemathe: “[laughs] That’s a good question. So– It’s difficult.”
That’s Michael Waltemathe, a theologian at the Department of Protestant Theology at Ruhr University in Bochum, Germany. Michael studies the connections between space exploration and religion.
Michael Waltemathe: “As a theologian, on the one hand, what you can say– or as a Christian theologian, on the one hand, what you can say is, we have been given stewardship of our planet and you can enhance that to stewardship of the universe, of the Solar System. You would– you can do arguments for that, theological arguments. And if you accept that, that we’ve been given stewardship, say, of the universe, then that still doesn’t solve the planetary protection problem, because we may be the ones who are– who have that mission to send out life into an uninhabited universe, or we may be the ones who need to understand stewardship as protecting the– what’s the word?– protecting the status of the universe, maybe uninhabited as it is now.”
And of course, that’s just the perspective of one of the many religions we have on this planet. We’ll be talking about religious and cultural issues in space settlement in an upcoming episode. But Michael also has an interesting perspective on the planetary protection problem because of his work with a group of scientists at the University of California Santa Barbara that are pushing this question beyond the boundaries of the Solar System.
Michael Waltemathe: “So the experimental cosmology group at UCSB, they’ve been working on using directed energy to send small craft into interstellar space. Basically using a ground-based or Moon-based or space-based laser to power a lightsail craft that could be very small but could also be scaled up and send it to interstellar space at roughly, they’re going for– trying to go for 20 percent of the speed of light. And that would bring it to the nearest star in about thirty to forty years. And then you could have some data sent back from there and maybe in forty years’ time, we would have some pictures from exoplanets around Alpha Centauri or even some more data about the system. And the idea behind that is, if you send a craft like that, that is a couple of centimeters or a couple of inches in diameter, has certain weight, and you would propel it to 20 percent of the speed of light, it would leave the Solar System in a couple of minutes or hours, but it would also give you the opportunity, if you could get life on board, to study what that means, right? Sending life at the speeds– at relativistic speeds, at one-fifth of the speed of light. And nobody’s ever done that. So, they’re doing nematodes and tardigrades because they’re very small animals. Tardigrades are about a fifth of a millimeter, so you could– you can see them with the naked eye. You can see nematodes with the naked eye, it’s as little– they look like little hairs. But you can train them. They have memory. And so you could see what that does to memory when they’re out there. But you can also have them hibernate or in case of the tardigrades, dehydrate them, and then rehydrate them and then they will come back to life. And so you can basically send them out there, have them dehydrated for the voyage, and then rehydrate them out there in interstellar space and do some research on them.”
Michael pointed out that this plan doesn’t call for actually landing on an exoplanet, so some of the contamination issues might be avoided.
Michael Waltemathe: “The problem is, if you send a craft out at 20 percent of the speed of light and the source of energy is a Earth-based laser, then you can accelerate it, but there is no way you can slow it down at the other end. Which, of course, solves the problem of planetary protection for most cases, right? If that craft comes into an atmosphere, it would just be– It would just turn into plasma with the power of a small nuclear device, so– It would just blow up, and then there won’t be any lifeforms left to contaminate another planetary body.”
A lot of planetary protection policies apply specifically to Solar System bodies, so this proposal is sort of in a legal grey area for planetary protection. Do the same rules apply to planets in the system next door?
Michael Waltemathe: “Yeah, and that poses also some ethical questions. Can we do that? Should we even do that? Because we don’t know there is life out there. Is that our mandate, or should we try not to do it? And it also has planetary protection issues within the Solar System. I mean, we are going to be accelerating those things within the Solar System, and if something goes wrong and that craft hits a Solar System body, then of course planetary protection rules apply.”
So, let’s say you want to go start a space settlement, but you want to try to avoid forward contamination, either because you want to protect future scientific discoveries or because you don’t want to hurt the cute little microbes that might be living there. What can you do? Well, it depends on where you’re going and what you want to do there. Here’s biologist Margaret Race again.
Margaret Race: “So if you’re going to the Moon, you don’t have to worry about planetary protection because we know it’s an environment that doesn’t have conditions for life. It’s not, quote, “habitable”. There’s no liquid water up there, there’s no atmosphere to speak of, and so if you send things up there it’s just like sending organic material, and anything– like anything else you’d send. So when you would say, “I’m planning a mission to the Moon,” the Moon is a low category, a Category 2 mission, that says, really, you just have to apply to, in our case, NASA’s Office of Planetary Protection, say, “I’m going to the Moon. This is what I’m going to do, what I’m going to bring, and I shouldn’t have to worry about planetary protection.” And the Planetary Protection Officer will review your materials and say, “Yep, that’s right.” And you can go ahead. Now, if you’re going to Mars, are you going to orbit? Are you going to land? Are you going to drill into the subsurface? Each one of those is different. And so the cleanliness requirements before launch are more stringent, depending where you’re going and what you’re doing. So that’s how it played out. It’s a categorization system and it doesn’t apply equally to everything.”
If you decide you do need to worry about contamination, there are different techniques you can try for sterilizing your spacecraft and equipment to prevent carrying Earth microbes to space.
Margaret Race: “Maybe you can use gases. Maybe you can use materials that have been heated so high that there’s no chance that anything could possibly be on them. Or the composition of the material is such that, you know, they’re gonna be, quote, “sterile.” So there’s many different ways to do it. And each country does it slightly differently. Just as different hospitals might employ different methods for ensuring that their surgical suites are cleaned.”
But you can never perfectly sterilize a spacecraft. Earth is teeming with life, even in the upper atmosphere, and some of it is pretty hardy. You have to decide what level of contamination is an acceptable risk.
Margaret Race: “And so you can see that these issues, when you’re talking about them in terms of legal and policy matters, and what you do to your spacecraft, it’s something like saying, “Thou shalt have clean air.” Well, “clean air” means a lot of things to a lot of people. And we didn’t consider carbon dioxide as a problem long ago when the Clean Air Act was signed. And so we add different pollutants as we find things, we consider adding scrubbers, or catalytic converters on the back of cars. So we’re looking for that blend of things. You can’t reduce it to zero. And even at the individual level, think about something like microbes and biological contaminants before you go into a surgical suite. If you don’t sterilize those tools before they cut you open, you could have problems. But there’s really no such thing as total sterilization, getting rid of everything. So how do get it down below a level where the risk is minimal? And so that’s the risk to who? An immunocompromised person? A person who’s very elderly or very young and didn’t have a flu shot? Or– So there isn’t just one answer and there isn’t just one method. You can sterilize things by using soap, you can sterilize by putting it into an autoclave and using steam. You can use alcohol wipes. You can– So there’s many ways to, quote, “sterilize” something. And the message comes from, all of it is just saying, you want “clean”. What does “clean” mean? Not that it’s dangerous, although it can be, but you want it clean. Now define “clean”.”
And things get even worse if you want to send humans into space. We’re also teeming with microbial life, and we can’t be sterilized! I asked Margaret if human space travelers complicate the contamination problem.
Margaret Race: “Ohhh yes. Absolutely. That’s exactly what’s going on right now. So NASA and COSPAR, the committee on space research– which is a scientific body that reports into the United Nations Committee on the Peaceful Uses of Outer Space– they have begun asking questions about, “Hm, if you’re gonna go to a place like Mars with humans someday, does that mean that we will totally contaminate the place?” …If humans go, we know that there’s no way we can put them in, totally enclosed systems. So what do we do about the contamination? Do you essentially autoclave everything that goes out? Is that even possible? Do you– How do you clean and maintain spacesuits? How do you keep the lab on the surface separate from the habitation area where the astronauts might sleep and work? And so there’s all sorts of aspects that have, essentially, these same questions about cross-contamination that we have on Earth. And so some of the questions can be taken care of by looking at the design of spacesuits or the venting from a habitation or something like that… The questions open up all sorts of topics. Even food supplies. And– you know? So you’re bringing up food for the astronauts. And you’re gonna put it up there ahead of time. What happens with the wastes that go–? Is that part of planetary protection or not? So all of these things, breaking down the mission into pieces and then looking at, what are the risks? What are the technologies we can use to mitigate it? What are the things we don’t really have to worry about? And how do we make sure that all the missions do things appropriately to protect the place where we’re going to study and also Earth when we come back?”
Philosopher Kelly Smith pointed out that we have a little bit of time before human settlements get started in space, and that we should use that time to try to find a consensus on how we want to handle these issues if we do discover life on another world.
Kelly Smith: “Before we’re there, let’s really think through first principles and decide what’s important. Now that does get immediately really complicated, because the problem that you encounter in ethics is, unlike in science, consensus is rare. You can get a broad consensus for things like, “Yeah, microbes are probably not nearly as valuable as multicellular organisms.” Though, there will be a vocal minority of people saying, “Wait a minute! You’re being unfair to the microbes!” Right? So even there. But you can get a broad consensus on that, but if you start asking questions about, you know, is it worthwhile to endanger, say, multicellular organisms in order to get some major but unspecified advance in science? That’s extremely unclear. And like I said, I think even the scientific community’s gonna fracture twenty-five ways to Sunday and people are gonna be arguing about how that’s due to science. You’re never gonna get perfect consensus.”
Kelly also emphasized that when we talk about these issues, we need to be clear on what our principles and values are.
Kelly Smith: “Unfortunately, when it comes to ethics, one of the first problems you run into is that people are just very vague and unclear about what they’re saying. One of my pet peeves is when you get in these discussions and someone will say something like, “Well, you should respect all life.” And I immediately want to say, “Well, what does that mean?” I mean, like, okay, I respect Bill the Microbe, but does that mean that I can’t disinfect my bathroom? Right? I mean, because if that’s what it means, I think it’s silly, and if all it means is I should feel just a tiny, little bit guilty when I disinfect my bathroom, okay. [laughs] So we have to be, I think, upfront about what the principles are, and then to the extent that we can, we have to try to build consensus. And if it’s not 100 percent, maybe we can get 75 percent consensus, or maybe we can get all the scientific community to agree that of the options on the table, this is the best one. But you won’t really know until you get into the messy debate and you really try to hash all this out. So that’s kind of what I’m arguing for. Let’s spend the next twenty years yelling at each other and trying to figure some of this stuff out. And then when we’re actually in a situation to make a decision, maybe it’ll be a bit clearer.”
So what do you think? If we find microbial life on Mars, how much effort should we put into protecting that life? Does Mars belong to the Martians, even if the Martians are only microbes, as Carl Sagan once said? Or should we treat Martian microbes with as little attention as we do Earth microbes? And how much should we worry about the scientific integrity of future discoveries of life in space?
Join the conversation on Facebook at facebook.com/makingnewworlds. Or hit us up on Twitter @makingnewworlds. You can also visit our website at makingnewworlds.com. Remember that Episode 12 will be our audience feedback episode, so please send in your written or audio commentary on any of the topics we’ve discussed so far if you’d like to be featured in the episode. Get your comments in by February 7th to be included.
Margaret Race can be reached at email@example.com, and would love to hear from interested students who want to work on planetary protection issues. Kelly Smith heads an organization called Social and Conceptual Issues in Astrobiology, or SoCIA, which is holding its second meeting this April in Reno, Nevada. He’d be happy to hear from anyone who would like to get involved. And Michael Waltemathe has co-edited a book called Touching the Face of the Cosmos: On the Intersection of Space Travel and Religion.
This has been Making New Worlds, a podcast by me, Erika Nesvold. Our intro and outtro music is by Herr Doktor.