I, For One, Welcome Our New Arsenic-Replacing-Phosphorus-In-DNA Overlords

mono_lakeYeah! This is just the sort of thing I’d hoped that we (human beings) would find soon, in order to strengthen the idea that in looking for forms of life elsewhere, we be not just open to the idea that the basic chemistry for that life may be very different from what we are used to on earth (easier said than done), but that it is maybe even probable that this is what we could find first. Now, given the news today (announced by Felisa Wolfe-Simon and her team in a NASA press conference today and reported on in a paper to appear in Science) we know that it is not just a theoretical construction, but already a reality right here on earth. The researchers have identified a life form with a striking difference. The bacterium (which lives in Mono Lake – see NASA image above right) has DNA (and some other important complex molecules) with a major difference from all other forms we know. phosphorus has been replaced by arsenic!

periodic_tableThis works, by the way, because arsenic is in the same chemical family as phosphorus, being directly below it in the periodic table. Note that this is exactly the sort of thing that has been speculated about a lot in the classic days of science/speculative fiction concerned with alien life, remember? :- Silicon based life forms instead of the Carbon based ones that we know and love on earth. Silicon is again in the same column as carbon in the periodic table (have a look – again, just below!), and so can play a lot of the same chemical roles in life as carbon does. So now we have a version of this for real, at least a little bit, with this discovery – the bacterium has found a way with dealing with its arsenic rich environment by using it in places where phosphorus would be normally used – and in some of its most basic life-defining chemistry.

While there’s lots of chatter on the web about how this proves that life forms here on earth could have come from elsewhere (no, no, no, it does not), and no doubt other outlandish (forgive the pun) things, the real significance of this for the space context is that while one can sit and speculate about all sorts of wild and wonderful life forms that are easier to imagine than detect (you kind of have to have some good idea of what to look for if doing a search), it is nice to know that it is possible to find at least variations on a familiar theme. This gives something concrete to circle out from, as it were, rather than just shooting in the dark in one extreme, or staying looking just under the lamppost in the other.

Have a look at the NASA announcement here. Read more discussion at, e.g., Not Exactly Rocket Science and Bad Astronomy.

-cvj

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