Biologists have long believed (or assumed) that we understand the basic physiology and metabolism of organisms, but this is based only on our current knowledge of molecular biology and metabolism from the organisms on our planet.
There is one popular and slightly likely possibility, however that could potentially shatter our understanding of the inner mechanisms and nature of life as we know it; the second genesis theory.
So, what IS a second genesis of life? Simply put, it is the life that doesn’t exist on the current phylogenetic tree which all living things we know of are mapped on; the second beginning of life with organisms of a completely different nature and metabolic/life processes from ours.
Granted, this could just as easily exist on Earth so what relevance does this have to space, you might ask.
The answer is, it completely changes the search for life as we know it- if a second genesis truly exists. All of our rovers, spectrometers and other diagnostic instruments are calibrated to identify patterns and telltale signs, based on our understanding of the organisms present in the current phylogenetic tree.
The possibility of a second genesis may be closer than we think- literally! One of Saturn’s moons Titan has lakes of liquid methane.
According to NASA Ames Research Center’s Dr Chris McKay:
“If there’s life in that liquid methane, it would be widespread, and it would affect the atmosphere, and you could see it in the hydrogen.”
The reason for this is because on Titan, chemical reactions that release energy similar to the kind that methanogens (microbes that survive in methane) on Earth may need (as an example) all require hydrogen. So the prediction is that life on Titan may require hydrogen to survive.
The Dragonfly probe (planned for a 2027 launch) is an 8-blade drone planned to set course to Titan- it has attached to it a mass spectrometer to search for chemical components (particularly those of importance to biological processes).
Another one of Saturn’s moons, Enceladus, has been theorised as a potential location for a second genesis of life to occur. There were jets of H2O on the moon discovered by the Cassini probe which according to a cold geyser model is due to pressurised H2O and hot rocks being in contact with each other. The resultant ejected water was a ‘soup’ of different compounds such as methane, ammonia, C6H6, C3 and C4 organics- and further research will not even require complex/expensive processes such as drilling into the surface as the material itself is ejected into orbit.
Currently, there is a joint mission between the US and Japan regarding Enceladus called LIFE (Life Investigation For Enceladus) which is in the works as well for further study of the moon for signs of life.
At the end of this all, the essential fact to take away is that with the likelihood of a second genesis of life being factored in, our current parameters of the search for life elsewhere in the universe and the methods we use to locate it will need altering, in order to account for this concept not previously considered as well as the ramifications it will have on future space programs and science.