The search for life elsewhere in our universe has long been a challenge to scientists.
Part of the problem is our reliance, as Earthlings, on what we might expect life to be like in other parts of the universe. Often, our ideas are colored by our expectations, which we draw from observation of "life as we know it" here on our home planet. But could life evolve and manage to thrive in other ways, and under vastly different conditions than Earth life has grown used to, if found elsewhere in space?
There are many places throughout our own solar system where it is hoped that life-giving conditions may be found. One of these is Saturn's moon Titan, which, like Earth, is covered in streams, lakes, and oceans... but of a variety very different from our own. Titan's liquid bodies, rather than being water, are instead filled with liquid methane and ethane, constituting a truly "alien" environment by all accounts.
Given these conditions, how could life come to exist in such an environment, or could it exist there at all?
According to new research, scientists are indeed hopeful that Titan may bear new kinds of life, despite its challenging environment. A study published in the Proceedings of the National Academy of Sciences, titled, "Polymorphism and electronic structure of polyimine and its potential significance for prebiotic chemistry on Titan," looks at the similarities, and the extreme differences, between conditions on Earth and Titan, and whether life indeed may exist there.
"Experimental and observational data suggest that hydrogen cyanide, the most abundant hydrogen-bonding molecule in Titan’s atmosphere, may polymerize on the surface to polyimine," the study's abstract says. "Using quantum mechanical calculations, we show that polyimine has interesting electronic and structural properties that could potentially facilitate prebiotic chemistry under cryogenic conditions akin to those on Titan."
According to the study's lead researcher, Martin Rahm, “We are used to our own conditions here on Earth. Our scientific experience is at room temperature and ambient conditions. Titan is a completely different beast."
At the crux of the research is hydrogen cyanide (also called prussic acid), a colorless, extremely poisonous and flammable liquid organic chemical; hardly the kind of substance one might consider "ideal" for the formation of alien life. The substance boils slightly above room temperature, but because it is able to react with itself, as well as with other molecules, it is capable of forming various polymers, which include a substance called polyimine.
Among its unique qualities, polyimine is able to absorb wide spectrums of light. Wide enough, in fact, to capture the scant light which pours through the dense haze of Titan's atmosphere.
This ability to capture light may help polyimine act as a catalyst for life, despite the extreme conditions in which it exists on Titan.
Still, while some view the presence of polyimine as favorable toward the existence of life on Titan, others aren't quite ready to go all-in on the idea. Dr. Robert Minard, a Penn State University chemist, told the Christian Science Monitor that it "is possible that the chemistry going on there could lead to self-replicating life forms, but it's difficult for me to see how that could happen because oxygen is such an important part of bio-molecules.” Oxygen is a requisite, at least in terms of life observed on Earth.
Will the eventual discovery of alien life have to rely on biology very different from what we're used to seeing on our planet currently? If so, there may indeed be unique varieties of evolution taking place in parts of our universe, and in the most extreme conditions, which will redefine our expectations of what, precisely, life is, and where we can expect to find it.