Too cool not to share...
I don't normally send mass E-mails, but something very cool is happening tomorrow (Wednesday) that I wanted to share with all of you. NASA is holding a press conference at 2 PM Thursday to announce something that, in their words, "will impact the search for evidence of extraterrestrial life."
The press conference will be airing live on NASA TV here.
If you're able to multitask at work, this could be a cool thing to watch. If not, it should be all over the science news by Thursday evening.
Internet rumors that they are announcing the discovery of life elsewhere in the solar system are sadly not true. But NASA has announced the lineup of scientists speaking at the press conference, and some Google sleuthing by me and other space geeks suggests what the discovery will be. Most likely, scientists studying a lake in the California desert have discovered a type of bacteria that uses arsenic instead of phosphorous in its biochemistry. More information on the research is available via the London Times, as well as via a paper by one of the scientists on the panel, Felisa Wolfe-Simon of the United States Geological Survey (USGS), describing the context of the research. This will give all the technical details if you have a background in biochemistry.
Oh, and here is the lake.
So that is the context, but there is still some suspense. The suspense is - how exactly does this bacteria use arsenic? And what does this mean for the search for extraterrestrial life? There are three possibilities, ranging from "hey, that's really cool" to "OMG, that totally revolutionizes our understanding of life."
Remember that arsenic and phosphorous are chemically very similar, but phosphorous is a key ingredient of every cell in the body, and arsenic is a deadly poison.* This leads to the three possibilities:
1) These bacteria are similar to, and evolved from, other bacteria; but have evolved the ability to use arsenic to keep themselves alive. This would merit a "hey, that's really cool," because something that's a deadly poison to everything else on Earth would be food to these creatures. But that's not the really exciting possibility...
2) It's also possible that, rather than just metabolizing arsenic, these bacteria are in a real sense made of arsenic. Meaning that, in molecules where other organisms (from bacteria to humans) have phosphorous, these bacteria would have arsenic.*** That would make them different from every other species on the planet.
3) If they do announce possibility (2), there could be something even more exciting in store. Evolution can produce a wide variety of adaptations, but it's hard to imagine evolution making such a basic structural change through natural selection based on mutations. That means that these bacteria could have formed from the inorganic primordial ooze independently from everything else on the planet - a second "creation event," if you like. Instead of being our evolutionary "cousins," they would be strangers. But even if this is objectively true, how would we prove it?
So what does this mean for astrobiology, the search for extraterrestrial life?
If they announce that they have discovered possibilities (2) or (3), it has major implications. We've looked all over the solar system for life, but we've always been looking for "life as we know it." These humble bacteria could be the first example of "life as we don't know it." There could be lots of possible ways to make life work. Non-DNA-based life? Life that doesn't have cells? The sky's the limit. Here is a very readable paper outlining the possibilities, but these are just the possibilities we can imagine.
The press conference is intended to support a paper in the journal Science, coming out tomorrow. Lastly. for those of you who are science fiction fans, I realized that the Star Trek original series episode "Devil in the Dark" [SPOILER ALERT] features the "Horta," an intelligent, misunderstood creature in which molecules in Earth-based life that contain carbon instead contain silicon, the element below carbon in the periodic table. If tomorrow we hear about possibility (2), then it's the same principle but with arsenic instead of phosphorous. [END SPOILER ALERT]
So, in summary, this is way cool. Thanks for reading as I geek out on it. I'll be watching tomorrow if I'm not in meetings, and you should too. If you do, send me a Gmail or Facebook chat.
-Drek's Awesome Friend
I have the coolest friends ever.
UPDATE: You can find NASA's article on the talk here. It doesn't clarify the issue of whether the arsenic-using bacteria derive from an independent abiogenesis event or not, but the description of the bacteria as otherwise part of a very common family of bacteria makes me suspect that isn't the case. Sadly, I wasn't able to stream the conference so I can't speak to that. Nevertheless, so very freaking cool.
*Geek note: Phosphorous is an important part of all three of the key molecules of life - DNA (genetic code), RNA (transmitter of genetic information), and ATP (provider of energy to cells). Arsenic is a deadly poison, and has been a choice murder weapon from the middle ages to today.**
**Geek note #2: Phosphorous (symbol P) is directly above arsenic (As) in the periodic table (in the same "group" - (see here.), meaning they are chemically very similar. In fact, this is why arsenic is a poison - arsenic "tricks" your body into thinking it is phosphorous, but they are chemically just different enough that arsenic can't substitute for phosphorous, and your body breaks down.
***Geek note #3: Phosphorous is part of the "backbone" of DNA and RNA, the thing that the information-carrying ACTG/ACUG bases attach to; and also part of the structure of ATP; in fact, the "P" in ATP stands for "phosphate." If arsenic were swapped with phosphorous, the structure of all three molecules would be the same, but they would be chemically different. ATP would be ACTAs instead.