MSL Curiosity is busy investigating the surface of Mars, to see if that planet could have harbored life. Image: NASA/JPL/Cal-Tech

The Puzzle of Planetary Protection

Article written: 28 Oct , 2015
Updated: 23 Dec , 2015
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The recent announcement by NASA confirming the presence of liquid water on Mars pulls planetary protection into the spotlight and is causing some serious head-scratching in the scientific community. On the one hand, having existing liquid water on the Red Planet is a cause for wonder, excitement, and a strong desire to investigate it in a great deal more depth to look for the possibility of life. On the other hand, there is the dilemma of protecting a potential biosphere from contamination from Earthly bugs. As keen as the Curiosity mission team is to take advantage of the rover to have a much closer look at recurring slope lineae (RSL), the rover itself is just not clean enough.

“There will be heated discussions in the next weeks and months about what Curiosity will be allowed to do and whether it can go anywhere near the RSLs,” said Andrew Coates of University College London’s Mullard space science laboratory. “Curiosity now has the chance, for example, to do some closer up, but still remote, measurements, using the ChemCam instrument with lasers, to look at composition. I understand there is increasing pressure from the science side to allow that, given this new discovery.”

It is a conundrum that is not new. If you send a spacecraft with the intention of finding life, how do you know if what you found was not brought there by the very thing you sent? This is known as ‘forward contamination’. There in fact rules set in place by a worldwide organization called COSPAR (Committee on Space Research), that anything sent into space are assigned to one of five categories in increasing order of risk. Naturally there are subcategories.

Curiosity is classed as Type IVb, whereas for it to take any samples from RSL, it would need to be Type IVc, thus an extra level of cleaning would be necessary. The rover can use instruments such as ChemCam to observe the flows remotely. Under COSPAR rules it cannot be allowed close enough to take direct samples. In fact there was a mistake made when sending the rover to Mars when some drill bits were not sent through the final stage of cleaning, whilst still very clean, procedure was not strictly adhered to.

Some scientists are now arguing that the level of decontamination is not only a lengthy procedure, but also expensive and pointless as microbes from Earth will already have landed on Mars via asteroid strikes thus be present already.

“We know there’s life on Mars already because we sent it there,” John Grunsfeld, the associate administrator of NASA’s Science Mission Directorate, said during a press conference last week.

In the paper, called The Overprotection of Mars, co-authors Alberto G. Fairén of the Department of Astronomy, Cornell University and Dirk Schulze-Makuch of the School of the Environment, Washington State University argue that the level of planetary protection needed to go to ‘sensitive areas’ would be prohibitively expensive to achieve.

In the paper, called The Overprotection of Mars, co-authors Alberto G. Fairén of the Department of Astronomy, Cornell University and Dirk Schulze-Makuch of the School of the Environment, Washington State University argue that the level of planetary protection needed to go to ‘sensitive areas’ would be prohibitively expensive to achieve.

“If Earth life cannot thrive on Mars, we don’t need any special cleaning protocol for our spacecraft; and if Earth life actually can survive on Mars, it most likely already does, after four billion years of meteoritic transport and four decades of spacecraft investigations not always following sterilization procedures,” Fairén says. “Planetary protection policies are at least partly responsible for the lack of life-hunting Mars missions since Viking, as they impose very stringent requirements for sterilization of the spacecraft which, in my opinion, are not necessary,” he adds.

You can do your best to clean your spacecraft, but you simply cannot eliminate it entirely. It is in fact possible that the high levels of radiation and UV light Curiosity has been exposed to, may have sterilized it enough; however is debatable as, in the process of cleaning the spacecraft, the decontamination team may in fact have inadvertently allowed the few organisms tough enough to survive the cleaning process, the trip and Mars’ extreme environment to adapt and live on the planet.

Doubtlessly, the debate will continue to rage on, particularly with the upcoming Mars 2020 rover mission in mind. It will certainly be fascinating to see what additional revelations Curiosity may reveal to help scientists solve puzzles such as this.


7 Responses

  1. permanently_ad_hoc says

    There is some pretty fuzzy thinking in the opinion piece, which can be found here: http://www.nature.com/ngeo/journal/v6/n7/full/ngeo1866.html

    The author basically asserts that if life brought by a rover can survive on Mars, then it doesn’t matter because Earth life has already come there.

    First, the few micro-organisms that could survive the shock, desiccation and trip to Mars inside a blasted rock are not necessarily the ones that can survive on Mars, past or present. The author simplistically refers to the incredibly vast array of Earth organisms as just “life” and treats them all the same. Examples – an E coli that survived the trip would have no host. A fungal spore would have no pre-existing organic matter to consume.

    Second, with the observations of the RSL “streams”, we know that the areas where liquid water is present on Mars is a truly miniscule fraction of the total surface area. This vastly decreases the odds that a viable Earth organism seeded Mars in the last 3 Billion years, but the author also skips over this.

    Third, if the author has his way, we would send unsterilized rovers to those rare places where there is water – the exact places where Earth life might have a chance. We would deliver a wide variety of organisms directly to the source, and those organisms would not have been down-selected by being able to survive being blasted off the earth in an asteroid strike, then surviving in a rock for millenia.

    Finally, if there is life there that came from the Earth eons ago, it has adapted to Mars. That would be extremely interesting in its own right. It makes zero sense to then introduce new Earth life there and mess up the existing ecosystem, both because of the irreversible loss in science and the ethical issue of contaminating a planet with the worst form of pollution – a self-replicating pollutant.

    • FarAwayLongAgo says

      Planetary protection is about avoiding contamination of a particular sample. It is like hygiene in a hospital. But since there’s no chance in H**l that two proteins evolve identically independently, it is very easy to identify contamination from indigenous life. It is not as if any lifeform on Earth would flourish on Mars and take over the planet (it required colonization for the pest to cross the Atlantic, for example). And even if it did, who are we to make any value judgement about it? Isn’t life good? Why should we prevent life from spreading?

      Interplanetary contamination is an interesting thought experiment, but nothing which should be considered for actual exploration.

      • permanently_ad_hoc says

        You wrote: “It is not as if any lifeform on Earth would flourish on Mars and take over”.

        You have heard of evolution, right? An an introduced organsim need only get a foothold, after which it might well have the capabilites to race past existing life. Mixing genes through sex, or epigenetic capabilities might well allow an Earth organism to take over from those that didn’t have them. As is has on our planet.

        You also wrote: “..who are we to make any value judgement about it? Isn’t life good? Why should we prevent life from spreading?”

        By all means, let’s let smallpox spread again. Let’s let the zebra mussel spread down the Mississippi. Until such time as a morally superior race or a god appears to make the decisions for us, we, as a democratic society, must make these value judgements.

  2. Bo Zo says

    I’m all for preventing contamination of Mars. Because A) If Mars has life, then contamination makes finding and studying that life more difficult; and more importantly, B) it would be an unforgivable shame if our microbes drove Martian life to quick extinction after all these billions if years.

    But until when? When will we know there’s no Martian life to disturb? How will we find out without risking its destruction?

    Can we risk -not- studying Mars? For how long? There are costs to that too.

    At some point we’ll just have to say “F*** it” and risk something.

    (How much testing has been done with microbes in Mars-like conditions in labs? Our microbes are fine tuned to live in very specific environments on Earth. Do any of them even stand a chance anywhere on Mars?)

    • permanently_ad_hoc says

      While there is an ethical argument that “Mars belongs to the Martians”, I do agree with both your and Albert B feelings on this and don’t think the uncertainty about extant life should stop us eventually sending humans there.

      I think the point at which we throw in the towel on the chances of there being life there, is at least after we’ve looked a bit, though. Viking’s life detection experiments were worthwhile, but probably defeated by the chemistry of the soil there. We know enough now to devise viable experiments and also we know likely places to look. It is a given that a negative result will not prove that there isn’t life under some other rock somewhere else, but at least we will have made a reasonable effort to preserve the science and any Martian ecosystem. I wish the NASA Mars missions actually went and looked for life, rather than beating around the bush with “follow the water”.

  3. AlbertB says

    Recently there was talk of sending people to Mars. Now these explorers would be living off the Martian land, growing crops, recycling wastes etc. How are the anti-contamination rules going to apply to this endeavor?

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