More on arsenic...
Hello again all. Just a quick update with my reaction to what today's NASA press conference actually said. Due to my sometimes-exceptionally-poor time management skills, I didn't get to see the press conference myself, but I've been following the news coverage, and I skimmed the Science paper announcing the results.
To summarize: the researchers collected bacteria from mud at the bottom of Mono Lake and brought them into the lab. They put them into petri dishes containing arsenic but no phosphorous, then transferred the microbes to new petri dishes until the phosphorous level was down to nearly zero. The bacteria thrived. When the researchers looked at important biological molecules in the bacteria (DNA and ATP), they saw that where you would normally find phosphorous, there was arsenic. This is the first time anyone has found an organism where one of the six major biological elements ("CHNOPS") were swapped out for another element. It shows that the possibilities for life are not as narrow as we previously thought.
Professional science writers have explained it more clearly than I just did. Here are a few examples from the Washington Post, the New York Times, the BBC, Wired (with an awesome analogy in the lede), LiveScience, and, of course, Phil Plait's Bad Astronomy (which is actually not bad).
Places you might not think to look for science articles, which shows how widely-covered this result include: Fox News, and hyperbolic as usual, Al-Jazeera (with video), and The Sun.
My quick-hit reactions:
1a) Of the possibilities I mentioned, #2 comes closest. It's different than I expected, and slightly less impressive. I had expected them to announce the discovery of life that incorporates arsenic in its DNA/RNA/ATP in the wild. Instead, it was a lab-based discovery.
1b) If I'm understanding correctly, the arsenic-incorporating bacteria evolved from the wild bacteria through artificial selection introduced by the researchers reducing the amount of phosphorous in their environment and increasing the amount of arsenic. Evolution = awesome.
1c) But that evolution likely would have never happened without the "head start" of the bacteria living in an arsenic-rich environment in Mono Lake.
2a) It's not accurate to say this is "arsenic-based life." Rather, it's life that looks biochemically just like the rest of life on Earth, just with most of the phosphorous atoms switched out for arsenic.
2b) Therefore, my possibility #3 is not true. These bacteria are a branch of the same tree of life as everything else is, and have already been placed into a Family in the Linnean classification system. We're still waiting for a genus-species name for them (as in Canis familiaris or Alces alces). May I suggest Horta californius?
3a) All that said, this is the closest example yet to "life as we don't know it." It's a fairly small substitution from the rest of life, but the shift from "life can only exist if it contains mostly the CHNOPS elements" to "hey, that could totally be CHNOAsS instead" is a profound one. (Although CHNOAsS would be a particularly unfortunate acronym.) If As can substitute for P, what else could be switched out?
3b) ...although, it should be noted that the bacteria still prefer "eating" phosphorous to eating arsenic. If you put phosphorous in the petri dish, they'll gobble up all the phosphorous and switch to arsenic only when they have to.
4) Switching carbon for silicon would be harder, because carbon and silicon are chemically more different than arsenic and phosphorous.
5) Picking up on one of the things a friend of mine wrote, an obvious implication is that these bacteria would be a great way to clean up arsenic spills. Consider that arsenic is a deadly poison to us, but is actually food to the bacteria. It's as if some actual intelligent aliens from another planet were looking for a species to clean up a highly toxic pecan pie spill. I'd totally volunteer for that job.
6a) As for the astrobiology implications, another of my buddies had another very insightful comment. He says: I was just telling [someone] something the other night actually, my long-time complaint about "what's this 'planets that can support life' business anyway? Life evolves to the environment, not the other way around." And here we are!
6b) That's obvious when you think about it, and it suggests that life could be even more common in the universe than we ever thought.
Science may make the research paper available to the public, outside their subscription firewall, tomorrow. There are actually two papers, both short. One is the full research report, written by the team and intended for biochemists. The other is a more journalistic article, written by a science writer for all practicing scientists, including non-biologists.
Lastly, I should have mentioned earlier, please forward this or my previous E-mail to any family, friends, co-workers, drinking buddies, or frenemies that you think might be interested. The more people hear about cool science, the better.
Actually, someone's thoughtful forwarding of yesterday's E-mail led to a friend-of-a-friend E-mailing me, which means I got to meet a cool person also. They also told me that their kidneys were stolen by a man with a hook for a hand that called in sick to work on 9/11. (That last part is a joke - see the third paragraph of this article).
So that turned into another very long, very geeky E-mail. Hope you enjoyed reading it at least 1/42 as much as I enjoyed writing it. :)
-Drek's awesome friend, whose DNA still contains boring old phosphorous
Boring or not, we're all just as happy he's around! As for me, I'll just note that this discovery is so cool, it made xkcd:
Now that's awesome.