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Redefining the structure of life

So I've spent the last few days stuck at a conference, furiously refreshing my phone to try and get the latest scoop on the "big announcement" that NASA unveiled last Thursday.  Now that I'm finally back to my normal schedule, I thought I'd add a quick update to exactly what has been found and what this implies for our understanding of life in the universe.

Firstly, we didn't find extraterrestrial life.  The reason I emphasize this is because people were speculating rampantly about this possibility, and it is obviously one of those things that might take on a life of its own if not handled properly.  That being said, you could say that we've accomplished the next best thing.

In order to understand this discovery you must know a bit about Arsenic, an element that is fairly common on earth, but which is poisonous to nearly all living organisms we've encountered.  This is because Arsenic exists in the row just below Phosphorous on the periodic table, meaning it can occasionally fit into the same kinds of molecules, displacing Phosphorous and causing a breakdown of function.

This is a problem, because Phosphorous is one of the most important elements in all living organisms.  It is often found in "phosphate" groups, an essential part of both DNA and ATP (the molecule that drives almost all energy expenditure in your body).  Without phosphorous to perform these essential functions, we've never found life that can proliferate.

At least, until NASA's recent announcement.

On Thursday, a large group of researchers from the US Geological Survey, the NASA Astrobiology Institute, and a host of other groups published a paper detailing a strain of bacteria taken from Mono Lake, California that has the ability to live off of Arsenic, rather than Phosphorous.

They accomplished this by taking samples of the bacteria and placing them into an environment that was devoid of Phosphorous, but had plenty of Arsenic.  I want to stress again that such an environment would be fatal to 99.99% of life as we know it, but these bacteria were able to grow and proliferate, incorporating the Arsenic into their biological makeup.

Why is this important?  Well, for one it serves as a proof-of-concept that we may need to drastically alter out assumptions about the necessary makeup of life.  Thus far, all of the data suggested that all life must be made up of essentially the same components, but the discovery of Arsenic-based lifeforms suggests that there may be considerable wiggle-room with respects to this statement.

This has important implications for understanding life on our own world, where we might expect to see other kinds of organisms that utilize the building blocks of nature in new and unexpected ways.  In addition, it suggests that we need to re-think our assumptions about what kinds of life exists in our solar system.  Earth organisms may use Phosphorous because of its abundance on our planet, but on other worlds it is not nearly so prominent.  Perhaps these extra-terrestrial organisms have adapted to utilize different elements in an entirely novel and fascinating way.

Regardless of any specific prediction, this is yet another example of just how valuable science can be in adding to our understanding of life.  It is also an example of the vast sea of ignorance that still lies before us.  Today, we have fundamentally altered our understanding of life and opened a new chapter in astrobiology.  Tomorrow, who knows?

Here's a NASA article about the finding and here's another good article summarizing the results

via Science

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