If you’re sending a probe to another planet, how can you ensure that there are no microbes hitching a lift? I spoke to Dr Parag Vaishampayan from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena about this, and a discovery he and his colleagues have recently had published in IJSEM.
Is there life on Mars? No one knows for certain, but NASA is doing its very best to find out. Multiple probes, landers and rovers have already visited the Red Planet to see if it has ever had the correct environmental conditions to support life. Indeed, the agency recently announced plans to send a new rover in 2020, with the express mission to search for signs of ancient life.
NASA missions don’t come cheap; the Mars Science Laboratory with its associated Curiosity rover, for example, cost a cool $2.5 billion. If you’re going to be spending all that money on future missions trying to find (evidence of) life on another planet, it’s probably best if you don’t put it there yourself.
Dr Vaishampayan works for the ‘Biotechnology and Planetary Protection Group’, a suitably futuristically-titled section of JPL, which has two main objectives: to prevent ‘forward’ and ‘reverse’ contamination. These are two sides of the same coin. Anything brought back to Earth from another celestial body with the potential to sustain life – hopefully Mars, definitely not the Moon – needs to be stored extremely carefully, to prevent any reverse contamination. As Parag explained to me, ‘We don’t want to contaminate our own planet, it’s the only one we have.’
While we’re not yet at the stage of sending any samples back from Mars, Europa or Enceladus, we are firing craft off into space all the time. Preventing forward contamination stops us from sending microbial life, or chemicals associated with life, to other planets – both of which would fool any detection experiments.
All satellites, landers and rovers built at JPL are constructed in the Spacecraft Assembly Facility – a set of giant clean rooms where technicians piece together these complex machines from their constituent parts. Although the rooms are controlled for temperature, humidity and airborne particle levels, and cleaned with harsh alkaline detergents and UV light, the technicians are not alone…
Parag’s job is to regularly assess the number and types of micro-organisms in the clean room. Repeatedly, he and his colleagues find extremotolerant bacteria – the hardiest of the hardy. These bugs are being constantly assaulted by cleaning products yet survive, despite there being, seemingly, no nutrients for them to consume.
Surprisingly, each spacecraft assembly facility has its own distinct microbial population. Researchers compared the microbiomes of JPL (California), Kennedy Space Flight Center (Florida), and Johnson Space Center (Texas) and found each was significantly different, with only a few species overlapping. If you ever happen to be confused about which NASA clean room you’re in, just look at its microbial community and you should be able to figure out where you are.
To top it off, the microbiomes of these rooms are constantly in flux, with fewer bacteria detected during spacecraft construction, when the cleaning regime becomes even more stringent than normal.
Where do these bugs come from? Perhaps unsurprisingly, the answer is from people. Despite being wrapped in suits that wouldn’t look out of place in an operating theatre, 90 per cent of the time the technicians are responsible for bringing bacteria into the clean room. If you sample for bugs outside the room, you’ll get an idea of what you’re likely to find inside.
Which brings us nicely to a recent paper published by Parag and his colleagues in IJSEM. While sampling the floors and equipment during the assembly of the Phoenix lander in 2007, the team discovered a bacterium whose only match in the DNA databases was from a bug isolated by European Space Agency researchers in a clean room in Guiana, South America. All tests on the samples from the two countries showed that this bacterium had very low levels of similarity to any other species and belongs in its own genus. It has since been named Tersicoccus phoenicis in homage to the mission during which it was isolated.
Unlike many of the species isolated in the clean rooms, T. phoenicis does not form spores to protect itself from its harsh environment. These super-tough shells protect bacteria in a state of stasis, until conditions become favourable for the spore to germinate and the bacteria to reanimate. The term ‘super-tough’ shouldn’t be used lightly. Spores of Bacillus pumilus SAFR-032, isolated from a JPL clean room, were sent into space, and spent 18 months stuck to the outside of the International Space Station, where they were battered by cosmic rays, magnetic fields, microgravity and high-energy particles. Remarkably, when returned to Earth, a few of the spores germinated.
If T. phoenicis isn’t surviving as spores, how does it remain so resistant? Parag suggests that the new species is likely to have a highly-developed DNA repair mechanism, similar to the posterbug for this group of extremeotolerant bacteria, Deinococcus radiodurans, which can survive massive levels of ionizing radiation.
Given that a variety of hardy species have been found in the clean room where spacecraft are assembled, and bacterial spores are capable of surviving extended periods in space, we have to ask the obvious question ‘have we sent life to other planets?’ Parag told me that he gets asked this question all the time, but was adamant in his response:
‘Do we have bugs on spacecraft? Yes we do. Have we contaminated other planets? The answer is no. The Biotechnology and Planetary Protection Group know that you cannot build a spacecraft in a completely sterile room, but we keep the number below a certain threshold, so that, based on our calculations, the probability of them surviving their interplanetary voyage and proliferating on another planet is effectively zero. Only then will the Planetary Protection Officer sign off on a launch.’
This is good news for us. Finding evidence of life outside our planet would arguably be the biggest discovery in human history. It’d be disappointing if it turned out to be a species we’d already met.
Vaishampayan P, Moissl-Eichinger C, Pukall R, Schumann P, Spröer C, Augustus A, Roberts AH, Namba G, Cisneros J, Salmassi T, & Venkateswaran K (2013). Description of Tersicoccus phoenicis gen. nov., sp. nov. isolated from spacecraft assembly clean room environments. International journal of systematic and evolutionary microbiology, 63 (Pt 7), 2463-71 DOI: 10.1099/ijs.0.047134-0
Moissl C, Osman S, La Duc MT, Dekas A, Brodie E, DeSantis T, & Venkateswaran K (2007). Molecular bacterial community analysis of clean rooms where spacecraft are assembled. FEMS microbiology ecology, 61 (3), 509-21 DOI: 10.1111/j.1574-6941.2007.00360.x
Vaishampayan PA, Rabbow E, Horneck G, & Venkateswaran KJ (2012). Survival of Bacillus pumilus spores for a prolonged period of time in real space conditions. Astrobiology, 12 (5), 487-97 DOI: 10.1089/ast.2011.0738.