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At first glance, it may seem that the question “What is alive?” in biology is answered in a way that leaves no room for doubt or hesitation. The fundamental axiom claiming that all living things are made up of cells is considered a simple and sufficient answer to understand this topic. This claim is valid for most living things on Earth known to science. But when it comes to the virus, the situation gets complex. Although the virus has typical life characteristics, it cannot act as an independent unit with its cytoplasm, enzymes, and its replication mechanism.
On Earth, there are living things even stranger than viruses: prions. Generally, prions do not resemble any cellular structure. This small and seemingly ordinary entity which at the same time causes mad cow disease is a protein that has a normal function in the brain. When the disease-causing form of this protein emerges through some mechanism in the brain, other normal proteins start resembling each other through a chain reaction, transforming into prions. In this way, prions reproduce and replicate themselves.
When trying to extend the living understanding of biology beyond the Earth to astronomical dimensions, the tip of the rope usually goes out of the hands of biologists and into the hands of physicists and mathematicians.
The most crucial thing a cell passes on to the next generation is information.
The definition of universal life should be based on the understanding of information. On Earth, micro-boxes of information carriers, which we call cells, adapt to the surrounding environment, accumulate their experiences, and pass them on to the next generation, mainly through genetic material called DNA (deoxyribonucleic acid). However, just as every monkey species undergoes evolution but doesn’t become human (mathematically, the possibility isn’t entirely non-existent but extremely low), elsewhere in the solar system the probability of primitive information-carrying genetic material undergoing evolution (chemical evolution) and transforming into complex DNA is also very low.
Although NASA is currently in search of life on Mars, in reality, it doesn’t exactly know what it’s looking for.
The criteria to determine whether what we find in space is alive or not are not well known to science. Since Mars is a neighbouring planet to Earth, any life there might resemble ours. According to a theory/hypothesis, it’s even possible that the origin of life on Earth traces back to Mars. Ancient bacteria inside meteorites, carried by rocks from nearby places like Mars, might have arrived here. However, the situation may be entirely different on Jupiter’s moons. And, I’m not even mentioning life born outside the solar system, on other stars, in other galaxies.
So, at its most basic, what does our current understanding of astronomical life consist of?
It should be noted that the existence of living structures, in general, is contrary to the universe, more precisely, the course of the universe.
According to one of the fundamental thermodynamics laws of physics, the evolution of a living cell in the universe, where disorder increases gradually (i.e., it is obligatory to increase entropy), is a force moving in the opposite direction. Evolution has led to the development of complexity in the universe, advancing from primitive protons, and ions to cells, from cells to seeds, organs, systems, complex organisms like humans, and even further to communities, civilizations, consciousness, and the ability to write sentences about oneself. These developments contradict the general trend of the universe, which is the law of entropy, where complexity decreases.
According to physics, a living being, within the vast canvas of the universe, is a small deviation from the rule at the micro level. I liken it to the waves hitting the rocks on the seashore, going back and forth quietly for their own, while suddenly "leaping" up to 5 meters.
Since such deviation in space is extremely rare, this information (complexity) that arises by chance should not be lost; instead, it should be passed on to the next generation step by step for continuous development. For this, a carrier is needed. On Earth, this carrier is DNA. In other parts of the cosmos, it will likely be a system with quite a different structure or could be. When the field of astrobiology in biology discovers this strange new molecule, fundamental biology textbooks like the Campbell Biology book will likely increase their volume by at least 25%.
Author: Araz Zeyniyev, Molecular Microbiologist, director of the Habitat Project
Mad cow disease (or its medical name “Creutzfeldt-Jakob” disease) - is a neurological disease found in ruminant animals (which can also be transmitted to humans) caused by prions. This disease leads to damage of nerve cells due to the abnormal accumulation of proteins in the brain, and over time, epitomises itself with symptoms such as loss of coordination, muscle weakness, and other neurological signs.
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