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

And in the future...

[Press2ToContinue]

will the Office Of Planetary Protection will provide condoms in which to encase the astronauts?

Re:And in the future...

[dgatwood]

Depends on whether they're down with OPP.

Already done

[able1234au]

Meteors from earth have probably peppered the other planets anyway. Some bacteria spores can survive inside them. So they are probably already contaminated. And in any case we could compare the DNA to see if it is from earth.

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:Already done

[the biologist]

As my handle suggests, I am a research biologist. Mostly, that just means I like to think about this sort of topic. Don't take it as me attempting to shut you or others down.

Your logic is more or less on the ball... DNA isn't made of amino acids. There are plenty of other nitrogenous bases which could have been used in DNA without any other complications. The paired bases do have to match up in a consistent way. Various forms of synthetic DNA has been made with alternate bases and it seems to behave like DNA in a physical sense.

I too prefer to think that the bases our DNA use has do do with which ones were most readily available, or which were most available in the little puddle where the biosystem started. Those basic organisms which started later or used things 'almost as good' got eaten in the endgame.

Similar logic comes in to play with the amino acids which we use to make proteins. There are many alternatives, several of which have been experimentally introduced into living biosystems. (There are E.coli which now use amino acids not found in any natural biological system; labs at University of Texas-Austin study this topic.) With amino acids, there is even more room for random chance in the initial choise of basic modules. Once that first living system started, it probably ate every other nascent living system. There is good reason to believe that amino acids will be used to form proteins and that a certain diversity of amino acids is needed, covering several basic chemistries, but that the specific amino acids isn't so important. (The E.coli types with chemically novel amino acids grow just fine.)

Re:Already done

[the biologist]

That is one of the things they're testing. They see an initial growth defect upon adding the new amino acid. Basically, every place the altered codon is found the resulting protein acts somewhat weird. Biology is flexible and the cells keep going anyway. After a short while, the cells get over the issue one way or another and there is no remaining growth defect apparent.

[A different experimental group...] If you have an ongoing culture and take isolates at incremental time points, the isolates show interesting behavior when compared. Each isolate will outcompete the isolate just prior when in a common culture, as expected. If you compare each isolate to the second back, most (but not all) will win. If you compare each culture to earlier isolates, it is essentially random which one will win. The expectation was that each isolate would outcompete all prior isolates...

The modified cells will lose to normal ones after the initial change... but once they have had time to get over the shock, it then becomes anyone's guess which way any particular competition experiment will go.

I think the group modifying amino acids is looking to convert them all to types not found in nature... resulting in E. coli with no natural amino acids. At that point, things start to get real interesting. Lots of aspects of our biology are tuned in some way to deal with the existing distribution of amino acids, so these highly modified cells will have lots of changes to lots of systems. Evolution is a really powerful thing. Once you start feeding the culture with less and less of the new amino acids, the cells will figure out how to synthesize them and do so efficiently. Some metabolic circuits will be tweaked, others will be scrapped and scrambled whole-sale.

Re:Office Of Planetary Protection?

[hawguy]

I'm so glad we put so much effort into protecting other planets.

Now how about we stop tossing radioactive shit all over our own? kthx.

I don't think that's NASA's department. You'd have to talk to the Department of Energy to ask them to stop letting coal plants emit so much radioactive waste products if your goal is to limit radiation release.

Re:better to err on side of caution

[viperidaenz]

First you need to give Mars a magnetic field to shield it from the radiation given off by the Sun, which also strips off any atmosphere that accumulates too. It's also pretty good at killing things too.

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!)

Re:Why bother?

[psithurism]

Ok, I'm not a complete nutjob here, and I understand two parts of why they bother, first the agency is there to protect our own planet from samples coming back: if the moon or Mars supported life for a few billion years it might become horribly invasive when brought back into the paradise that is our planet, so there is that. Second, they don't want a bacteria covered microscope looking for Martian bacteria because that would kinda nullify the results.

But anyway, I care. I personally feel that we have a responsibility to do whatever we can to take life off this planet ASAP. What if earth is rendered uninhabitable by some unforeseeable cosmic event? As far as we know life is unique to this planet and it would be kinda a bummer to see it all get wiped out when there was a chance to let it restart somewhere else. I'm morally opposed to protecting other planets from ourselves.

The whole article they talk about taking care of the solar system for future research, but fuck future research; if we successfully dropped life onto another planet, that would be way more interesting than our typical: "this rock has more iron than that rock," and I really see no need to save those rocks for our great grandchildren at the expense of creating alien life.