Protecting the Solar System From Contamination

tcd004 writes "An article at PBS begins, 'Imagine this crazy scenario: A space vehicle we've sent to a distant planet to search for life touches down in an icy area. The heat from the spacecraft's internal power system warms the ice, and water forms below the landing gear of the craft. And on the landing gear is something found on every surface on planet Earth... bacteria. Lots of them. If those spore-forming bacteria found themselves in a moist environment with a temperature range they could tolerate, they might just make themselves at home and thrive and then, well... the extraterrestrial life that we'd been searching for might just turn out to be Earth life we introduced.' The article goes on to talk about NASA's efforts to prevent situations like this. It's a job for the Office of Planetary Protection. They give some examples, including the procedure for sterilizing the Curiosity Rover: 'Pieces of equipment that could tolerate high heat were subjected to temperatures of 230 to 295 degrees Fahrenheit for up to 144 hours. And surfaces were wiped down with alcohol and tested regularly.'"

Comments

Re:Already done

[Fluffeh]

Actually, you should read up on the topic before you go spouting nonsense.

Transfer of Life-Bearing Meteorites from Earth to Other Planets for example.

Re:Already done

[garyebickford]

IANA physical biologist, but I did look into this question a bit from a systems point of view a few years ago. The key thing would be the minimizing of the energy required to sustain the structure while at the same time allowing maximal adaptability. Or, more abstractly, the 'fitness' of each amino acid pairing for the general task.

There is certainly a large element of chance, but it's probable that the four amino acids that ended up being used are pretty close to the optimal set. This derives from a general evolutionary model, where various things happened by chance, and the ones that worked best for the situation (I could have said 'survived' but that carries too much baggage) would tend to be the ones that were incorporated.

Otherwise, one is arguing that a single chance pairing of amino acids just happened to work, and no others were (in an analogous sense) 'tried' in the right conditions. To my mind, it's more likely that many combinations came together, and one was more successful. It might even be that there was a sequence of such cases - maybe (hypothetical example) when the G and C bases bond together, they float better in a solution with a pH of 7.2 or some such thing.

I prefer to think that certain bases were more available, or just happened to work better under the conditions, and so they got used while others that were 'almost as good' didn't, or didn't for very long. In this case (again with little biological background), things like requiring just enough energy to be split apart, or fitting just right together with the splitting mechanism, or any of several other criteria including environmental ones such as 'in this temperature and pH range') would all be factors. I suspect some very interesting analysis and experiments could be done on this.

Re:alcohol? doesn't kill them all

[the biologist]

90% ethanol leads to bacterial spores precipitating out of solution, which is why clinical labs use 70% ethanol to sterilize surfaces. The lower dosage leads to faster overall kill rates because the spores stay in solution where the ethanol can disrupt their processes.

Re:but rats still got every where

[garyebickford]

I think the analogy stands. Consider the tardigrade, an animal composed of 40,000 or so cells (every adult has the exact same number of cells). They have been shown to survive freezing to near 0K, heating to over 130C, and the radiation and vacuum of space outside the ISS (or was it the Shuttle?).

The point is that for a given potential infestation, the bugs only have to succeed once. Sterilization measures have to be 100% successful every time. And they aren't, can't be and won't be. Even if we never actually put humans into space again, every vehicle will contribute it's little pile of DNA. Each halving of the number of impurities left on a surface increases the cost, difficulty and effort by an order of magnitude. (hmm - this is much like the 90% rule of software!)