With the simultaneous announcement of a possible nitrogen-based, cell-like structure allowing life outside the “liquid water zone” (but within a methane atmosphere) announced by researchers at Cornell (academic paper) and the mystery of fluctuating methane levels on Marsraising the possibility of methane-respiring life, there now exists the possibility of a whole new branch of the tree of life that does not rely on either carbon or oxygen for respiration. We may find evidence of such life here on Earth down in the mantle where “traditional” life cannot survive, but where bacteria has evolved to live off hydrocarbons like methane and benzene.
There’s a lot in this post, all relating to life and methane. The first is about a study of possible life that might exist in liquid methane (instead of water), which is a possibility in the outer solar system, notably on Titan, a moon of Saturn and the largest one in the solar system. The average temperature on Titan is about -179 ºC, below the boiling point of methane. On Titan, methane may flow like water does on Earth, in rivers and lakes.
The idea that there may be methane life in the universe has been around for a while. The new model seems to lend some support to the idea, but I think it’s important to understand that this is only a hypothetical model. If methane based life does exist on Titan, I wonder at what stage it would be in its evolution, since life is chemistry, and chemistry at -179 °C (94K) seems like it’s going to flow a lot slower than chemistry at 15 °C (288K). If there is life on Titan, I think it’s likely still in the relatively early stages.
Mars is cold by our standards, but it’s not far enough from the sun to be cold enough for liquid methane. Methane is a gas there, just like it is here. My understanding is that the significance of methane there may be as a possible waste or by-product from some kind of life, much as it is from some life on Earth. The methane on Mars may still be from non-living natural processes, like volcanoes. Only time will tell.
The article on life in the lower levels of Earth’s crust is interesting. I think it got included here because that life may feed on chemicals like methane. Again, this is different than what’s being envisioned as a possibility for life on Titan, but still pretty fascinating, particularly the possibility that life may permeate down into Earth’s upper mantle.
I think all of this goes to show that we have reasons to believe that life can exist in a wide variety of environments, and that only looking for it in narrow habitat zones may be too limiting. Personally, given the wide variety of what we call “life” here on Earth, I suspect that when we do find the first extraterrestrial life, it may well challenge our very conception of what life is. We may end up debating whether or not it actually is life, or just some kind of previously unknown complex chemical processes.