a reply to: Bfletcher618
I've never heard them say that we MUST find oxygen because life ONLY breathes oxygen. Sciences know for a fact that life does not need oxygen because
for the first 1/5 to 1/4 of the history of life on Earth, that life was anaerobic life (life that does not use oxygen, and in fact finds oxygen to be
It was not until about 800 Million years after life first emerged did oxygen begin to appear in abundance in the atmosphere and life on Earth began to
evolve to use oxygen.
What you probably heard them say was that the search for life on exoplanets will probably revolve around astronomers looking for an abundance of
oxygen in the atmospheres of those exoplanets (they can analyze the atmosphere by analyzing their light spectras).
The reason they search for oxygen is because as far as anyone knows, the only way to get a relative abundance of elemental oxygen in an atmosphere
(such as the Earth with it's 20% oxygen atmosphere) is through life processes. So if they detect a certain level of oxygen in an exoplanet's spectral
analysis, then that would strongly suggest life.
That's how they plan to find life -- by looking at the balances of chemicals and elements in an atmosphere, and look for unbalances that cannot be
explained by other natural (non-life) processes. The reason they search for oxygen is because it is "Life as we know it"
, and life as we best
understand it. "Life as we DON'T know it"
would be harder to search for, because we wouldn't even be sure what to even look for.
However, that does not stop some astrobiologists for looking for "Life as we DON'T know it". For example (and as 'dat1059' in the post above me
alluded to), Chris McKay from NASA suggests that certain chemical imbalances of hydrogen and Acetylene in the atmosphere of Saturn's moon Titan could
possibly suggest a weird for of microbe that consumes hydrogen and acetylene on Titan. Granted, as McKay points out, there are non-life processes
that could explain these imbalances, but his [point is that it COULD be due to life.
Here is a NASA article about that:
NASA -- What is Consuming Hydrogen and Acetylene on Titan?
This lack of acetylene is important because that chemical would likely be the best energy source for a methane-based life on Titan, said Chris
McKay, an astrobiologist at NASA Ames Research Center, Moffett Field, Calif., who proposed a set of conditions necessary for this kind of
methane-based life on Titan in 2005. One interpretation of the acetylene data is that the hydrocarbon is being consumed as food. But McKay said the
flow of hydrogen is even more critical because all of their proposed mechanisms involved the consumption of hydrogen.
"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth," McKay
said. "If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from
water-based life on Earth."
So no -- you would be extremely hard pressed to find a serious scientist who says "Life can only exist by breathing oxygen".
edit on 23/4/2017 by Soylent Green Is People because: (no reason given)