Evidence of 100,000-Year-Old Life Found In Antarctic Subglacial Lake

Researchers taking advantage of retreating ice shelves in Antarctica have discovered evidence of life that's been sealed away for nearly 100,000 years. Lake Hodgson on the Antarctic Peninsula, once covered by over 400 meters of ice, is now obscured only by a thin layer three to four meters thick. Scientists carefully drilled through the ice and took samples (abstract) from the layers of mud at the bottom (as much as 93 meters below the lake's surface). "The top few centimetres of the core contained current and recent organisms which inhabit the lake but once the core reached 3.2 m deep the microbes found most likely date back nearly 100,000 years. ... Some of the life discovered was in the form of Fossil DNA showing that many different types of bacteria live there, including a range of extremophiles which are species adapted to the most extreme environments. These use a variety of chemical methods to sustain life both with and without oxygen. One DNA sequence was related to the most ancient organisms known on Earth and parts of the DNA in twenty three percent has not been previously described."

Re:Reprieved !

[Samantha Wright]

Not likely! While I don't really want to go through the exact details of it (I've had hilariously long and protracted conversations about this before), liquid water and the chemistry of the common non-metals (hydrogen, oxygen, nitrogen, and carbon) at temperatures where water is liquid have some fairly special properties that make them really well-suited to giving rise to life. Ammonia instead of water seems possible, but a few sci-fi staples like silicon-based lifeforms are extremely unlikely—and given the fickleness of what we know about abiogenesis, it's likely that any emergent life that starts off using anything unfamiliar will optimize toward something more similar to what we have. Strange things might be possible, but it's pretty likely alien life will be... compostable (if not edible) by us Earthlings.

Re:Reprieved !

[Samantha Wright]

Yeah, that's the biggest difference between "compostable" and "edible." There are a lot of detritovores that don't care about the chemicals they're chewing up; unless it's something toxic enough to kill them, anything just looks like a carbon chain in dire need of stripping. Molecules of the wrong chirality definitely fit in this category.

That being said, chirality isn't the only thing that you can count on being totally arbitrary. The choice of amino acids is pretty fickle (humans only have 20, some species have two more, and we often modify them... and there is a more-or-less infinite number of them that nothing on Earth uses at all. [wikipedia.org]) Nucleotides are similar [wikipedia.org], and the debate about nucleic acid backbones is open [wikipedia.org]. There are countless opportunities for different preferences amongst sugars (we're designed around glucose, rather arbitrarily) and other metabolites. In a real-life validation of all of this, Archaeans don't even use normal phospholipids in their membranes [wikipedia.org]! (Which seems like such a bizarrely difficult thing to do that I sometimes wonder if it isn't evidence of multiple abiogenesis events, but that's a bit flimsy.)