Curiosity and the Issue of Planetary Protection

Curiosity at Centre of Attention During Testing Image Credit: NASA /JPL – Caltech

There have been many reports about the possibility of NASA’s Curiosity rover contaminating Mars with microbes from Earth once it lands on the Red Planet in August. The wheels, the landing procedure and the drill bits have all come under scrutiny. But what are the concerns and what safeguards are there to prevent contamination from this or other missions?

In 1967 the United Nations drew up the ‘Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Bodies.’ All countries which sign up to the treaty “shall pursue studies of outer space, including the moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination.” Every mission is given a category (I,II,III,IV or V) depending on whether it is a flyby, orbiter, lander, or Earth return mission, whether its destination is a planet, moon, comet, or asteroid and whether the destination could provide clues about life or have the potential to support Earth life. So for instance Cassini is a catagory II mission, Curiosity is classed as a IVc mission.

Every stage of a mission is carefully monitored. From construction in a sterile clean room with laminar-air-flow systems, pressurized microbial barriers and personnel wearing hoods, masks, surgical gloves, booties and protective suits called bunny suits. Components and entire spacecraft are sterilized using dry heat microbial reduction, by being enclosed in a bioshield (like a large casserole dish) and baked them in an oven at 111.7 degrees Celsius for 30 hours. For more sensitive components a low-temperature process is used. Components are placed in a vacuum and hydrogen peroxide is injected into the sterilization chamber to establish a specified vapor concentration. Thousands of samples are taken at every stage of construction and tested for spore-forming organisms, for example the Viking mission in 1975 tested more than 6000 samples in total.

Three issues have arisen with the Curiosity rover. During the landing procedure a parachute and thrusters will slow the descent before the ‘sky crane’ lowers the rover, its wheels making direct contact with the surface. Previous rovers have waited on landing platforms for days before their wheels made contact with the surface and in tests it has been shown that even a few hours exposure to Martian levels of ultraviolet can kill between 81 and 96 per cent of bacteria that may be present. So once Curiosity lands it will probably need to remain stationary for some days to minimize the risk of contamination from its wheels.

Another issue arose last year, after launch, when it was realized that a step in the planetary protection measures wasn’t adhered to during the manufacture of the rover’s drill bits. These were meant to arrive at Mars inside a sterile box, but the box was opened and the bits tested for contamination and one of the bits was attached to the drill head. This procedure strayed from earlier agreed-to protocols. The drills have now become another cause concern as it has been found that Teflon and molybdenum disulfide from seals within the drill assembly could rub off and mix in to contaminate samples excavated during operation, making the samples more difficult to analyze. The MSL team are looking at ways to work around the problem, these could include running the drill on a slower, less percussive setting or dispensing with the drill altogether and relying on Curiosity’s scoop to take soils soil samples and using the rover’s wheels to roll over and break open rocks.

This all serves to highlight the importance of the planetary protection treaty to ensure we do everything possible to reduce the risk of contaminating other worlds and of compromising any data we return.

Find out more at NASA’s Office of Planetary Protection

62 Replies to “Curiosity and the Issue of Planetary Protection”

  1. Wasn’t the recent issue contamination of the sample with teflon, not with microbes? The teflon would make it more difficult to tell if their were microbes in the sample, but it wouldn’t actually “contaminate” Mars.

      1. It isn’t certain, but protocols were not strictly followed so the sterilization process is now in question. This came to light just after the launch.

      2. It is technically inaccurate to call it sterilization, as nothing will be sterilized. Even autoclaves have been found to not suffice for some extremophile spores, and of course not for most prion diseases.

        Your previous “microbial reduction” seems about right.

    1. It is the lapse in planetary protection procedure that could cause contamination. The separate Teflon and molybdenum disulfide issue could compromise the data analyses.

      1. Sorry for the late reply (dunno if you’ll actually read this):

        I understand that, but there are actually two issues here. One is a contamination issue that last made the news in Nov 2011, and the other is a problem with Teflon shedding in a sample, making analysis more difficult.

        The article you wrote (and, to a MUCH greater degree, mainstream media articles) conflated the two issues. Your article… kinda… separated the two issues, but not as much as it should have.

        Speaking of not adhering to protocol;), generally issues like this are caused by a lack of adherance to long recognized editing procedures. Proper editing of an article is very difficult, but it is an essential part of the article writing process. Peer review of articles by fellow writers can reduce this problem, though it doesn’t remove the need for professional editing.

      1. the whole 2.5bn drilled down through its wheels.
        Who wants to say, choose an atmospheric burn and crash trajectory for the rover to avoid contamination?
        My guess: land, pray and definitely believe that the precautions work.

      2. Overstating much? These are minor concerns compared to doing the mission in the first place.

        This is mostly standard routine and scientificaly verified.
        Yet, you don’t want people to start throwing petri dishes full of microbes up and shrug. There is still the international treaty to adhere to.
        Mars now, probably Europa next … you really want to know that the life you found is alien to Earth. Not Send another probe worth bn’s and clean the 2nd one a bit more thoroughly.

      4. If “this” (what?) is verified, give refs.

        In my first comment here I commented specifically how (a very unlikely) crosscontamination isn’t a do or die thing for astrobiology, because of genome sequencing.

      5. You searching for being right or you implying we’re going to send one of those things up // or keep sending rocks down to Earth until there is one with life …. hoping the end result will show “no contamination from curiousity (or future exploration probe)”. >>
        Lets see, lucky shot, 1 additional mission to where curiousity landed, grab a rock, bring it back, bingo, earth originated life. At least the sequencing is relatively cheap.

  2. This article doesn’t make clear how or why the Curiosity rover’s wheels might have become contaminated.

    Could perhaps do with an additional paragraph explaining this between covering off the hot & cold sterilisation methods and the section on touchdown via the Sky Crane?

    1. No sterilization, no matter how careful can ever be 100% certain. All we can hope to do is minimize the risk.

  3. The surface of Mars may have some decontamination abilities. With UV flux from the sun and perchlorate regolith I suspect any Earth microbe would have a difficult time there. This would be the case for a tiny innoculation. A manned mission to Mars though might dump enough biocontaminants so that some might make it to the subsurface and survive.

  4. the notion that we will contaminate the cosmos!
    freezing temps in near vacuum, UV and high energy cosmic rays notwithstanding.
    i wonder if we will hear of air pollution concerns on the moon?

    1. There has been several instnaces where satelites and other craft sent to space have been found to be contaminated by bacteria from earth and still been viable after several years exposed to the radiation and vacume and cold of space.

      1. Nope, it has never happened to my knowledge. There was an instance when they found spores inside a retrieved moon camera, but later research shows that it was probably contamination between the return trip and analysis. (This should be googeable I hope, which is how I found it. Perhaps in Wikipedia?)

        But if you have refs, it would be interesting.

  5. Agreed, but I am wondering what is special about wheels. Wouldn’t the same contamination issues apply to the bottom of the landing platform of previous rovers, and in this case to the skycrane vehicle?

    1. I believe the issue is that the wheels will then move across the planet (hopefully for some time & distance) as with Spirit & Oppy, while the landing platform & sky crane will stay where they land. It is a question of minimizing the risk.

      1. The pressure will be to move on, and the best way to sterilize the wheels is to roll them to be exposed to UV thoroughly instead of having them buried in the soil.

        I’ll bet they won’t wait.

      2. They could build hydraulic jacks into the rover to raise it and the wheels into the air just far enough to clear the carrier. (like the system Indy cars use) Then rotate the wheels slowly for a few hours when they are being bathed in UV light.

    2. I think Ethan was asking why the wheels are of greater concern than the other parts of the rover & landing device?

      My guess is because the under side of the landing platform & rest of the skycrane will have been exposed during decent. Plus the wheels have a larger chance of depositing the little buffers under the soil where they have the best chance to take hold.

      I personally think they take the whole contamination risk a little bit far. If there is life there it would be far better equipped to deal with the environment on Mars than anything born on earth. I would think the odds on a earth microbe out competing a Mars native on Mars would be close to nil.

  6. contamination ??we must spread life as far out as we can into the cosmos before we decimate this planet

    1. Agree. The only worries should be while searching for life and studying their ‘may be’ findings. At the same moment we have a permanent colony on Mars, or any other body, all enviromental worries will be thrown out the airlock.Literally. As it should be. All heavens are for us to settle.

      1. By God. It’s the mandate of life itself that it spread into every possible niche. Every organism on our planet does this. Our species is the vector for microbial life on this planet to spread forth into the solar system. It’s inevitable as long as we (as in the US, Russia, China, Europe, etc.) have a space program. Our planet has suffered plenty of mass extinctions thanks to the space debris thrown our way. It’s only fitting that we counter this by spreading the life on this planet outward.

        You can call me Hitler, fascist, or any other word you deem to be an insult. It will only make me laugh because it means you have no counter argument and can only react with emotion. I like the high ground myself. The view is so much better up here. And to be honest, I sort of feed off of your kind of reaction. It amuses me.

      2. Well I will not call you names! Someone with such a tenuous grip on reality might go over the edge when confronted with arguments based on science rather than superstitious religious dogma.

      3. I love it! There you go again attacking the person rather than his arguments. Is this because you have nothing of substance to say? I do believe this is a pattern to your comments. Can you break out of this? Or are your reactive emotions always in control? Is that how you win an argument by putting in the last zing? Now send me over the edge and break my tenuous grip. “Break on through” I always say. Let’s hear some arguments based on science. My reference to God was metaphorical by the way. Is your next comment going to be about me again? If so well, I can use another laugh. I like being entertained but I also like thoughtful discussion as well.

      4. In your first comment you say you are trolling (“any” reaction, “feed off”). If you cared about the content of a comment it would be simple to reply.


      5. Trolling wasn’t my intent. I was neutralizing the man’s way of responding to opinions that differ from his own. His adolf hitler response to squidgeny was the motivation for my first comment.

        If I were a troll, I wouldn’t be responding to you as I am now but would be goading you. I do care about the content of a comment and will demonstrate that but it depends on the nature of his next response. If it is more of the same (ie insults), I will let the man be.

      1. Rights and privileges are typically granted downward from a superior level – humanity has no such superior (barring beliefs in gods). Rights at a species level are for us to grant ourselves.

      2. I am sure Adolph Hitler felt the same as you. Yours is one of the most fascist statements I have ever read on this site! And there have been quite a few.

      3. That’s a bit of a harsh reaction… I would appreciate it if you could rebut my point instead of simply comparing me to Hitler.

        If it helps, let me give you some examples that I feel lead me to my conclusion. I have a right to an hour-long lunch at work – that is granted to me by my employer (my superior). Some people don’t have that right, because it hasn’t been granted to them. My pet dog has the right to run around in the park without a leash – that is a right granted by me (her superior).

        Some rights are self-granted. I grant myself the right to eat chocolate creme eggs for breakfast. A nation’s people (in some cases) grants itself rights through a democratic process. Nations grant themselves rights – sometimes by themselves only if they have no superior concerning the right in question (eg. the right to launch a satellite) or through UN processes (eg. the right to put economic sanctions on another nation)

        The UN is probably the closest we come to having rights at a species level – and we do so by granting them to ourselves. If this is not the case, then where do the rights come from? Who grants them to us? If the right is somehow “inherent”, then what evidence is there that it is so?

  7. Guys: How do these concerns of microbe contamination square with the discussion that downplays the possibility of panspermia in other threads ?

  8. how does everyone overlook the fact that the gov authorized this vehicle to be nuclear powered…oh no microbes?….this is ridiculous. If something goes wrong you are staring at the first nuclear disaster caused by humans on another planet. Naturally the public, including myself, dont know the extent of how bad this event could be. Maybe you should all point your finger at me and say, take your pessimism elsewhere, as i laugh at a world of people failing to recognize basic truths. If you mentioned to nasa the thought of sending a nuclear device of any sort to any planet even probably 15 years ago, i bet the notion would have been laughed at. I just dont understand how something of this nature could ever be approved in my lifetime. Maybe I dont understand the nature of how nuclear power works in devices like this and submarines, etc. But just the thought has me up in arms.

    1. It’s a nuclear reactor – it’s just a bunch of well-sealed containers of plutonium, which gives off heat because it’s radioactive. The heat is used to generate electricity. Look up radioisotope thermoelectric generator (RTG for short). The system is designed to survive an explosion of the launch vehicle without leaking, so there isn’t a whole lot that can go wrong. And the approach has been used many times before, such as on the Voyager deep space missions, Galileo, and Cassini. I was going to say that this is the first time they’ve been sent to the surface of another body, but that would be incorrect as the Apollo lunar landing missions used RTGs to power the science experiments they left on the moon.

    2. Yes, clearly you should panic if you don’t know much about something.

      THEN, after your panic has subsided, go to your library or start reading Wikipedia on the subject that you don’t know much about, if it gives you so much anxiety.

      Knowledge is power… over yourself.

    3. The Voyager probes launched how long ago again? Each of them has an RTG (using plutonium) and they have been running since the 70s, IIRC, though their power output has dropped since they were launched.

    4. Don’t forget the Viking landers, no. 1 and no. 2 from the mid 70’s. Both carried RTGs for power. Even solar powered vehicles such as the Mars rovers contained little capsules of plutonium to keep their insides warm. They are technically not reactors, just slugs of decaying elements that give off heat and easily-contained radiation. With thermalcouples, heat is converted into electricity. Very different technology.

    5. These are not nuclear fission reactors, they are thermal generators powered by radioactive material with a halflife on the order of decades.

      If you mentioned to nasa the thought of sending a nuclear device of any sort to any planet even probably 15 years ago, i bet the notion would have been laughed at.

      Oh, like how NASA sent these devices to Mars powering the two Vikings 36 years ago? Or how the Russian Mars 96 craft carried them (though it failed at launch)?

      Or how they have been used from everything from lunar rovers (two failed Cosmos missions 1969, see the link, who instead burned up in our atmosphere), to 5 of the 6 moon missions 1969-72, to the Galileo craft that was crashed into Jupiter, to the Cassini craft that will be crashed into Saturn?

      The extant and extinct MERs have radioactives for heaters and, more importantly, in the instruments exactly as MSL will have. Because you can’t make some experiments without them, at least small enough to get to other planets. You would need lugging multiton and megawatt particle accelerators instead.

      “To minimize the risk of the radioactive material being released, the fuel is stored in individual modular units with their own heat shielding. They are surrounded by a layer of iridium metal and encased in high-strength graphite blocks. These two materials are corrosion- and heat-resistant. Surrounding the graphite blocks is an aeroshell, designed to protect the entire assembly against the heat of reentering the Earth’s atmosphere. The plutonium fuel is also stored in a ceramic form that is heat-resistant, minimising the risk of vaporization and aerosolization. The ceramic is also highly insoluble.”

      “28 U.S. space missions have safely flown radioisotope energy sources since 1961.” Add to that the long list of known accidents from navigational, military and research crafts, where very few released contamination; I count 3 releases out of at a guess 100s of missions by now.

    6. thanks guys, now i just need you to explain how the star wars satellites use tesla energy to direct laser beams at rocket boosters long enough to burn through using the notion that a reflected light wave particle carries the information of velocity and vector.

  9. You can’t make an omelet without breaking a few eggs.

    We can’t look for life unless we go. The cost of a few microbes on the wheel of a rover? How about how bad it would be if a human lander crashed and split open, killing the crew and leaving their billions of microbes on Mars? I daresay now the few microbes on a wheel looks pretty good!

  10. As for the crosscontamination issue, from an astrobiology standpoint it is both understated and overblown.


    – The heating protocol, which I believe largely MSL has not passed through as it is a large structure with many heat sensitive components, is from before it was recognized that extremophiles survive the so called “sterilization”.

    This is presumably why it is now called “microbial reduction”.


    – Many crafts have already contributed massive amounts of spores on their chutes and especially within their bodies, which the protocols permit for practical and economical reasons. Some early russian Mars crafts were not undergoing the protocol at all, I believe. You can’t achieve null crosstransfer of life.

    – The surface of Mars is sterilizing.

    – Crosstransfered life are often specialist, but even if generalist not adapted to the environment.

    — Hence extant indigenous life would simply use them as a handy source of organics.
    — If no extant life is around or in case the invader survives against all odds, we could always sort out the crosscontamination issue by genome sequencing. It would not be an ideal situation, but manageable.

    The drill issue seems more serious than I expected.

    Considering not using the putative organics contaminated drill bit (in case they didn’t test it; finger prints’ fatty oils transfer easily between surfaces) until later is one thing. Plenty of uncontaminated science would be done first.

    But considering not using the expensive and needed drill at all seems a setback. I hear the measured organics level from a hard used drill is about the one expected to see if they find fossil organics. So it is a real problem, and I thought there was a better mitigation.

  11. How are you going to “sterilize” humans? I guess 1967s treaty has already put an end to humans exploration era… 🙂

  12. after another pipeline ruptured in alberta last week dumping nearly 1/2 million litres of oil into the red deer river, i’m more concerned about how we’re contaminating our own planet than if a few microbes find their way to mars via curiosity.

  13. The search for et-life on Mars – the only more easy accessible and promising place for this kind of search – has been screwed up by NASA after they were routed by the promising Viking results and retreated to geology topics in Mars exploration to this date. Of course there is the problem of contamination with every landing mission so it would have been wiser to finish the search for life first before doing geology research only while contaminating the planet a little bit more with each successive mission .

    How life forbidding is the surface of Mars – how important is planetary protection?

    1. it would have been wiser to finish the search for life first before doing geology research only while contaminating the planet a little bit more with each successive mission .

      Mars is a big place – even if we thoroughly contaminated one spot by dumping a pile of dead rabbits on it, chances are good that other spots (where we might find indigenous life) will remain unaffected.

      1. The test of evolution is now extended to the test of crosscontamination – dead (precambrian) rabbits.

        I like it.

    2. The consensus was that the Viking experiment results were _not_ “promising” but experimental artifacts. Otherwise NASA would have been clobbered by the science community and probably a lot other interests,

      Your suggestion is in spirit a conspiracy explanation, always the least likely explanation for anything by construction. (Attempting to shy away from testing.)

      1. Oh my conspiracies..conspiracies – small and large scale – have and always will be part of human history. You should be a little bit more careful in estaminating likelyhoods of these. There are a lot of interests behind this kinds of research so who knows what happened behind the scenes during the Viking times – a time of the cold war – which triggered the consensus you mentioned. A consensus which is by the way increasingly challenged nowadays and even back in time – why?

        Actually I would not be too suprised if Nasa tried/tries to cover mistakes related to Mars science they done in the past (and maybe even now with Curiosity) for integrity reasons etc. Credibility/integrity is of the most value for institutions like Nasa – i know you know that. 🙂

        Anyway, looking forward to the discussions about the Curiosity flight data in regards to organics with all that contamination issues in mind – will be fun.

  14. I believe that if we ever get to other solar systems and land on any exo-planets, or planets in our own solar system, there will be a huge need for exo-biologists. When we come across Life in the universe, (and eventually we will) There will be no way of knowing if it will be benign or if we run the risk of disease from new biological agents. (Look to the lessons learned here on Earth in our exploration of the New World) As for the risk of our own biological contamination of other worlds: This is something we should take very seriously. There are people that will say earth organisms will not compete successfully with the local microbes. (do you know this for a fact?) Who knows what niches are available to earth microbes? And visa-versa, what exo-biologicals can make inroads into our bodies and eco-system. The answer to these questions is: We don’t know! That is the main reason for exploration, to answer these and other questions. It would be in our own best interest to prevent ANY contamination from occurring in either direction.

    1. We do know, we are running likelihoods based on observed biology.

      It is highly unlikely any other biosphere’s organism can thrive in our bodies which constitute a very specific environment. And our adaptive immune system is just that. Infection isn’t even on the horizon realistically, before a virus or bacteria adapt to infect it has been going at it a very long time.

      Going in the other direction, it would be scaremongering to propose it is dangerous when the majority of what we know says it isn’t.

      Yes, minimizing contamination makes the astrobiology easier. But it also makes exploration and colonization harder or impossible, so it isn’t (has never) going to happen.

Comments are closed.