Are we solitary in the cosmos? The response to one of humanity’s most profound inquiries is made complex by a fundamental truth: If there exists life on other planets, it might not resemble what we know. A collection of stones from Mars or another celestial body will almost certainly not display recognizable fossils or other similarly clear indicators of living beings, remarked Mikhail Tikhonov, an assistant professor of physics in Arts & Sciences at Washington University in St. Louis who investigates microbial communities.
However, the possibility of not identifying indicators of life on a distant moon or planet does not imply it is truly barren. “There could be organisms out there that surpass our comprehension,” stated Tikhonov.
The quest for life that eludes our understanding may appear to be an insurmountable task. In a study published in Nature Communications, Tikhonov and co-author Akshit Goyal from the International Centre for Theoretical Science in Bengaluru, India, introduce a novel concept. Rather than searching for specific molecules or compounds linked to life as we comprehend it, researchers can seek distinct patterns of energy.
Tikhonov elaborates on his extraordinary concept in this Q&A.
What fundamentally defines life? How do living organisms differ from non-living entities?
We have no insights into the appearance or composition of extraterrestrial life forms. Yet there are two universal agreements: Living entities must consume and convert energy, and they must possess the ability to replicate. That’s about as precise as we can get to describing life.
When searching for quantifiable signs of life on other planets, we need to make further assumptions. We assert that any living entity is highly improbable to exist in isolation. It will almost always be a component of an ecological community competing for resources.
Couldn’t we identify life simply by searching for evidence of organic compounds or other biological indicators?
It’s crucial to understand that the compounds we designate as ‘organic’ are not solely exclusive to life. They can also arise without biological influences. More importantly, there’s no basis to believe that an alien life form would necessarily utilize the same molecules that we do.
How can we detect life on other planets if we are unsure what we seek?
That’s precisely the query we endeavored to address with our recent publication. Instead of chasing any specific molecule, we recommend investigating distinctive patterns across numerous molecules.
Chemical compounds vary in the amount of energy they store. On Earth, living beings decompose high-energy compounds such as glucose into lower-energy results like carbon dioxide.
Life tends to prioritize the breakdown of high-energy compounds first. Organisms that utilize more energy-dense resources will outlast and replace others, resulting in a specific kind of layering, with compounds organized by diminishing energy levels. The appearance of the organisms is irrelevant — as long as self-replication and ecological competition exist, we anticipate this pattern to emerge.
Layered structures can be produced through various processes, both living and non-living. However, only life exhibits this energy-centric ordering, so energy-ordered layering would be exceptional. These patterns are prevalent on Earth. Our hypothesis is that if a rock from Mars or another world displays this identical pattern, it is a strong indication of life involvement.
When discussing extraterrestrial life forms, how unusual could it potentially be?
Some individuals argue that there are not many ways to construct a living entity, so independently evolved life might still resemble Earth’s bacteria or even ourselves. But as a theorist, my role is to consider what else might be conceivable. What if on some far-off planet, life functions on an entirely different scale? One could envision a mile-long entity drifting in some remote atmosphere. The potential is vast, making it an intriguing subject to ponder.
Originally published on the Ampersand website
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