NASA’s astrobiology announcement wasn’t based on happy snaps from Mars, Saturn or any of the speculation flickering around the net. Instead, it was something much more important in many ways.
This Earthly discovery won’t instantly mean a lot to people looking for direct examples of life on other planets. The link to astrobiology is that it means that life based on chemistry quite different to Earth is quite possible. The fact is that cellular mechanisms based on totally different mechanisms is now proven.
This is ET's birth certificate. The new discovery is actually a massive slap in the face to the “no life elsewhere in the universe because we say so” brigade. Exactly how this collection of unelected, unasked nobodies got such a say in the debate about life in the universe is also unknown, but this is proof positive of them being definitively wrong even about life on Earth.
Arsenic is toxic. It kills most animals. This bacterium uses it instead of a fundamental life chemical, phosphorous. Humans use phosphorous compounds for practically everything to do with life. Potassium phosphate, magnesium phosphate, calcium phosphate sodium and iron phosphate are critically important compounds in the body. Without them, humans would be jellies, with no bone and nothing like the nervous system. Other phosphate based chemicals like ATP are critical energy managers.
So an organism which can use arsenic instead of phosphorous is a very big deal. This microbe is one of a family of known organisms, with “normal” biology, but this one has remodeled its entire set of biological processes to use arsenic.
The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.Note: NASA explains that arsenic is “like” phosphorous, follows the same pathways as phosphorous, which is what makes it poisonous. They're not that much alike in terms of chemical functions, however- until now. Phosphorous is 15 on the Table of Elements, Arsenic is 33. It’s a much bigger atom, and the chemistry is correspondingly complex. For a microbe to move from phosphorous to arsenic is like taking a cow which usually eats grass and getting it thriving on a diet of cluster bombs.
This is also an evolutionary marker, clear adaption to a deadly environment. Organisms which live in environments low on phosphorous tend to develop alternate mechanisms. Australian native trees, for example, are used to a very low phosphorous environment. They still use phosphorous, but use it sparingly and efficiently. In fact, too much phosphorous is dangerous to these trees, which can't handle it in large quantities.
This organism, which is native to a highly alkaline environment, has taken things a step further and replaced the phosphorous with something which ought to be a poison. Arsenic is a complex element with a range of chemical bonding properties, most of which are the reasons it’s a poison. The fact that a living organism can use it as a replacement for phosphorous is a very strong argument for a completely different range of biochemical compound, meaning life where life wouldn’t be expected to exist.
For astrobiology, it’s a wake up call. Looking for “organic chemicals” of the types known on Earth is now definitely no longer the only show in town. Life based on elements which usually aren’t part of life chemistry on Earth is the message. This life can be truly alien, based on combinations of chemicals unlike anything known on Earth.
It means life could exist in the hot acidic hell of Venus, based on sulphuric acid and sulphur compounds. It could exist in the freezing Martian dust, and even in environments which look too impossible like the gas giants, provided the chemistry works to promote life in some form.
The NASA announcement doesn’t quite mean “Go look for anything in the Table of Elements that moves”, but almost. This was a truly significant announcement, but it may take a century for that to be realized.
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