Though MSL was not designed to be a life-detection mission per se, let’s suppose for a moment that Curiosity finds traces of life on Mars. How could we make sure that the microbes we find are not coming from Earth, brought to Mars by our own spacecraft?
It’s known that certain microbes can survive the hostile conditions of space including ultraviolet light, cosmic rays and dramatic shifts in temperature. In an 2008 experiment, microbes were placed on the outside of the ISS to see how they would cope with this environment. 553 days later, many were still alive. [ref]Beer microbes live 553 days outside ISS:
http://www.bbc.co.uk/news/science-environment-11039206[/ref] That’s quite impressive and shows that a contamination of Mars could be possible.
I talked about this with Dr. Catharine A. Conley, NASA’s planetary protection officer. Yes, she definitely has the coolest job title on Earth! Based on Article IX of the outer space treaty, her office is responsible for minimizing the biological cross-contamination resulting from the exploration of the solar system.
What has been done to protect Mars from contamination
Protecting Mars already begins with choosing the right landing site. Gale Crater, in addition to being the site preferred by science, was also preferred by planetary protection. Says Dr. Catharine A. Conley:
Gale Crater is very near the equator, and observations suggest there is a minimal chance that the Curiosity rover could contact water ice near the surface. Without water, in the conditions at Gale Crater, there are no known Earth organisms that could grow.
It’s not possible to eliminate all microbes from a spacecraft, but the number can be greatly reduced. The entire MSL spacecraft was cleaned to ensure only a minimum of Earth organisms was transported to Mars. And some parts, like sample-acquisition hardware, were heated to sterilize their surfaces. At temperatures ranging from 110 to 146 degrees Celsius, some components have been baked for up to 144 hours.[ref]Mars Science Laboratory Mission and Science Investigation:
http://www.springerlink.com/content/2234421w50090w9u/fulltext.html#Sec44[/ref]
Dr. Catharine A. Conley:
We measure heat-resistant organisms that grow on a particular kind of petri plate as a proxy for cleanliness, because this allows spores of Bacillus bacteria to grow and these organisms are known to be among the most resistant to the space environment. The requirement, using this proxy, is that there be less than 300 ‘spores’ per meter of spacecraft surface — in practice, quite a lot of the time the MSL planetary protection team measured zero spores. This means that the assembly personnel did a really good job of keeping the spacecraft clean, by wearing proper gowning, wiping things down with isopropanol as they were working, and covering the hardware when they were done.
Technicians and engineers in clean-room. Image source: NASA
The MSL mission has been classified as a Category IVa mission,[ref]Category IV description at the Office of Planetary Protection:
http://planetaryprotection.nasa.gov/about-categories#4[/ref] allowing no more than 300,000 spores in total on the landed system (including the rover, parachute and back shell). So although the NASA team has done a great job cleaning the spacecraft, there still could be some microbes left to contaminate Mars.
What if we find traces of life on Mars?
Let’s make it clear: Curiosity is not designed to directly identify organisms on Mars – there’s no microscope to look at Mars soil and search for bacteria. But instruments like ChemCam can identify chemical compounds which could indicate potential biosignatures or past habitable environments.
Dr. Catharine A. Conley:
The challenge, with any mission, in identifying possible Mars life and telling the difference between that and possible Earth life, is to be able to do follow-on experiments — because any set of measurements we make at first is much more likely to provide hints and raise more questions, than it is to give a definitive answer.
Take the Viking mission for example, two probes sent to Mars by NASA in 1976. They carried three different experiments designed to determine whether life exists on Mars. One of them came out positive for life, the other two came out negative. So in 1976 there was no definite answer and until today the question is still open.[ref]Life on Mars Found by NASA’s Viking Mission?
http://news.nationalgeographic.com/news/2012/04/120413-nasa-viking-program-mars-life-space-science/[/ref]
Curiosity’s SAM instrument can look for organics in Martian soil by heating up samples to even higher temperatures than Viking did. So we might get some good answers from Curiosity – but we’ll most likely also get a lot of new questions.
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I’m astonished at the apparent lack of care shown by NASA scientists and engineers, but I’m also curious about the origin of this information. I can’t find anything about it on official JPL or NASA sites, but the media is reporting it everywhere. So what is the source of the information?
As to the Viking mission results, I’m very surprised that no follow-up work was planned for the Curiosity mission. Measuring methane outputs probably will give some indications as to the existence of microbial life, but surely some kind of excavation work would be needed in order to back it up.
I read about remarks being made about the instability of Mars’ inclination due to the lack of a large moon. While I agree that this would certainly preclude the possibility of the evolution of any higher forms of life, I don’t agree that it would prevent the genesis of microbial life. If, as it appears has already happened, water IS discovered just below the surface of Mars, surely life will be discovered there, protected from the radiation coming from the Sun and immune to the vagaries of living on a planet whose inclination alters radically across the aeons.
Unfortunately, I don’t believe the Curiosity mission will achieve anything of actual worth. Yes, it may prove beyond doubt that there was surface water on Mars billions of years ago, but this is barely relevant to us at this moment. It seems to me that NASA is unable to really focus on priorities when drawing up funding projects: searching for evidence of water 4 billion years ago in no way helps us to understand Mars today. Likewise, sending rovers to trundle aimlessly over the Martian surface would only make sense if the data provided was used to draw up viable future plans for serious scientific research into the habitability of Mars, its possible uses as a resting and filling station for future missions to the moons of Jupiter and Saturn, where the likelihood of life existing is far greater, and for ascertaining whether or not there is actual Martian life below the soil surface.
Sadly, I don’t believe that any of these important priorities will ever be properly catered for under NASA’s financing programmes. The SETI programme, whose probably scientific worth is close to zero, is still swallowing up large amounts of funding that could be far more adequately and suitably used in searching for life within our own solar system, instead of searching for it light-years away in the cosmos.
We will never know the rate of incidence of life arising in our galaxy. The likelihood of us ever discovering life outside our own solar system is minute and, frankly, beside the point. We need to know whether life ever arose, or is still arising, within the reach of our physical technology: Mars, Europa, Venus, Titan, Enceladus, even Triton. Even if we discover that this life is a result of Panspermia and that all the life forms discovered are essentially the same as those on Earth, we will at least have a solid basis on which to start seeking signs of life around other stars. At the moment, however, the cart has been placed firmly in front of the tired old mare in order that astrobiology experts – a meaningless term and a subject devoid of real, measurable content – can continue to receive grant awards in order to think up ways life could evolve, for instance, on a water planet – evidence of which is totally lacking, both for that sort of planet, and for any form of life outside the planet Earth.
And now, it appears from the world media, Curiosity may not only kill the cat, but could also seed life on Mars, presuming that there isn’t any indigenous life there at the moment. If there is, Earth-originating microbes could plausibly kill it off. Either way, the gaffe on NASA’s part is horrifying, but not, unfortunately, very surprising, since the organisation seems to be held together by sticky-tape, spit and the electromagnetic force between its component particles. Logical, thought-out processes seem to be missing. And because of this, when it is finally discovered that the Curiosity mission was both a waste of time AND money, calls for funding for better prioritized life-seeking missions will be ignored or turned down by a tax-paying public sick to death of spending billions on cosmic exercises in futility.