When the mars rover and other exploratory missions set out to find life on other planets, what is it exactly they are looking for?
Faces in the landscape
The list above has yielded very little insight into life on other planets.
How do we find life? what does it mean to be alive?
This has lead to a shift in how astrobiologists try and find life on other worlds. They now look for the chemical signature of life. They look for metabolites. They search to see if metabolism took place here. They look for the products of the TCA cycle and maybe one day their analogs. CO2 may very well be more insightful than O2 when searching for something that yields energy the way we do.
Oxygen, water, and a face are not necessary to be alive. The ability to pass along protons in a sequential manner is.
Metabolism is the defining feature of life and we are damn lucky to get to learn about it.
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