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Invasion from the blue planet: are we protecting Mars too much?

Are we overprotective of Mars? That is the claim made by Alberto G. Fairén and Dirk Schulze-Makuch in a recent commentary in Nature Geoscience. They argue that current planetary protection policies that try to prevent bodies in the solar system from becoming contaminated by Earth-life are too costly, inhibit scientific exploration and might actually be unnecessary because of natural contamination. How much value does a pristine non-terrestrial environment have?

Avoiding tripping up the science

While there are some concerns about back-contamination the current issue is about forward contamination: accidentally adding Earth microorganisms to a new environment. The main reason given in the 1964 COSPAR resolution was that the search for alien life is an important objective of space research, and contamination would make it far harder. The Outer Space Treaty enjoins signatories to avoid “harmful contamination”, where the harmfulness is apparently interpreted mostly as interfering with future experiments.

Fairén and Schulze-Makuch argue that the cost of sterilization is hindering Mars missions, especially to regions where Mars life could exist (or Earth life survive). The bureaucracy is preventing research because it tries to safeguard the ability to do future experiments.

They further argue that if Earth life could contaminate Mars, it has likely already done so. (and vice versa.) Whenever a sufficiently large meteor impacts Earth debris is thrown into space, and some of it is likely to be both contaminated by bacterial spores and big enough to protect them in space. While the transfer time might be measured in hundreds of thousands of years, this is not a major problem for frozen spores. While the amount of exchanged material per year is small, there has been life on Earth for 3.8 billion years – it adds up. Also, sterilization on Earth is not perfect (in fact, a new species of bacterium has been discovered living in spacecraft assembly clean rooms! The protocols are actually probabilistic and aim at keeping the probability of contamination reasonably low for a foreseeable number of missions.

The value of the environment

The real moral question is of course not about science tripping itself up by contamination or too much bureaucracy, but whether an alien non-living environment or living ecosystem must be protected.

The value of an environment has been a topic in environmental ethics for quite some time. Leaving out instrumental value and anthropocentricity (let’s assume no human will ever go to Mars or benefit from whatever is there) what is left is whether there is some intrinsic, non-anthropocentric value to an alien environment. Deep ecologists would clearly argue that the beings in an alien ecosystem have intrinsic value, and some would argue that even an a-biotic environment has a value, even though there is nobody around to experience it. Others, like Peter Singer, would argue only the sentient or living beings matter. Alan Marshall and others have argued that collective ecological entities have intrinsic value beyond their constituents, even when they are non-living. Depending on theory there might hence be value of organisms in themselves, in their uniqueness, and in the special relationships in the ecosystem (or even in the structure of the a-biotic environment).

If it is correct that spores are exchanged between Mars and Earth at irregular intervals, then it might not matter if some extra organisms arrive via space probes. The local biosphere (if any) would have evolved largely on its own, but with occasional infusions of new life. The only concern would be if the contamination accidentally introduces some invasive organism that destroys what has independently evolved or its relationships.

The fact that humans can choose to act differently visavi another planet, that is the important part, not whether it is a natural or artificial process. In a sense, a species becoming technological and visiting other planets is just a rare natural process, just like lithopanspermia.

A consequentialist might dislike a destructive contamination outcome but point out that it could have happened because of natural exchange too. As long as the contamination damage was not foreseeable the actions leading to it would have been morally acceptable. A deontologist might however argue that undertaking actions that risk a biosphere’s value are impermissible: we as moral agents must act in order to not risk value. Both would argue in favor of not being careless, but how strongly we need to care of course depends on how much value we ascribe to the planet and its contents.


But there might be another twist to the issue. Only a few people ascribe intrinsic value to an a-biotic environment, while many more think that living beings themselves have value. If we were to accidentally or deliberately seed an a-biotic environment with self-sustaining life (ecopoiesis) we might actually add a lot of value! A biosphere can contain a vast number of organisms and hence matters a lot, and if it has additional value from their relationships the importance goes up even more. Maybe we ought to be rolling our space probes in mud and filling them with lichens rather than sterilizing them!

This cheery view of ecopoiesis is of course not undisputed, but most opponents of terraforming planets have been arguing in favor of the rights or value of putative pre-existing life rather than non-interference with the existing a-biotic state. Still, Rolston suggested that any object of formed integrity generated by spontaneous construction from the laws of nature should be preserved. However, his view has a serious problem: humans and their weird behaviors are also formed integrity. By removing the agent/object distinction the preservationist view makes it hard to see why one kind of project of spontaneous construction should reign itself in in favor of another kind of spontaneous construction. However, there may be value in diversity: having a biosphere and a non-biosphere is better than two fairly similar biospheres. Unfortunately for the argument they would soon diverge: life on dry and cold Mars would adapt and evolve to become its own thing, very different from life on wet and warm Earth.

If there is a valid take-home message in the criticisms of terraforming it is that one ought to respect certain systems – systems of beauty, contingent history, ongoing creativity, or with a high degree of integration – and approach them cautiously. But that is not an argument for keeping life to Earth and maintaining the rest of the universe pristine: the wild and expansive biosphere of Earth with its metal and plastic offshoots is also worth allowing to sprout. There will always be plenty of a-biotic worlds out there. Life is far better at becoming unique formed integrity than any other known natural system (except, maybe, human minds) and is able to produce structures with intrinsic value. So ecopoiesis might be a good thing that adds vast amounts of value – but it should not happen by accident.



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6 Comment on this post

  1. I very much doubt that we’re in any more danger of “contaminating” Mars than we are of contaminating the moon. Mars is a dead world (due to its general physical characteristics – temperature, atmosphere, highly oxidising surface etc). If life could take hold on Mars it would have done so a long time ago. And terraforming is old-school sci-fi, utterly impractical and utterly pointless.

    1. Hmm… a lot of bold empirical claims there. Would you feel comfortable with policies set by people making this type of bold claims in (say) biosecurity, computer security or nuclear safety? There is certainly no shortage of them.

      1. Bold? No, conservative. We have sent many probes to Mars and the empirical results = no trace of life found. And the conditions we have found there are perfectly in accord with there being no life, i.e., it would be very surprising if there were any life. How it comes to be that philosophers confuse conservative empirical claims with “bold” ones, is probably best known to themselves.

        1. Back in 1974 or so, an influential US report on nuclear safety concluded that the risks were less than one chance in a million of a serious accident per reactor and year. It was based on the best evidence and expertise at the time. How surprising should we find Harrisburg, Chernobyl and Fukushima given this report? The chance of 3 accidents in 40 years in 400 plants given this is essentially 0 (it is a 23-sigma event; the expected number of disasters over this time is 0.016). Either we should be amazed by the unlikelihood of the world we live in… or we should conclude that there were flaws in the report.

          Empirical and theoretical arguments can bound probabilities, but they also have the risk of being erroneous (and we have piles of examples like above). If the probability that an argument is wrong is much bigger than the probability P it deals with, our posterior estimate of the real probability after hearing the argument should not jump all the way down to P, but just move a bit towards it. Jumping all the way to P is the bold leap of faith, because it presupposes the argument is 100% right.

          In most cases this does not matter: probabilities are large, or the consequences of being wrong are possible to live with. Things change when dealing with low-probability high impact events like existential risks, or in this case accidentally seeding/destroying a biosphere. If you think contaminating Mars doesn’t matter much, then things are all right. But if you think it actually matters a lot then you should want to have *really* good evidence. That is the conservative approach.

  2. Perhaps the ‘Philosophy Now’ article you link to covers this (I can’t tell; it’s behind a pay-wall), but one argument against terraforming is that it is plausible that animals in the wild suffer a great deal, so we shouldn’t promote their proliferation beyond Earth:

    I can’t help but find the deep ecology claims regarding the intrinsic value of abiotic environments to be rather bizarre and incomprehensible.

    1. If the suffering of animals is so bad that it would be wrong to add another biosphere, we should probably consider de-terraforming Earth too.

      (Although I think David Pearce has a more constructive idea in trying to re-engineer every organism to not have aversive experience; whether that is possible – conceptually, practically, ecologically – is of course an open question.)

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