There are many definitions of life, but most of them are based only on the origin of life on Earth. But what will life look like on other planets?
Science approaches this topic in different ways. A geneticist who works with organisms and their genomes has a completely different view of what life is than an astrophysicist, for example, who has a broader, more expansive and universal view of the same question. Earth-based definitions of life mean that what intelligent and conscious alien life can be like almost always essentially reflects how we imagine it on the basis of our humanity.
However, much about how life arose on Earth is still unknown. Researchers still don’t know whether DNA or RNA was the first genetic material, or whether life came from what is known as primary soup. It was believed that this “soup” is a mixture of organic and inorganic molecules found on the surface of the Earth, or it comes from energy moving from deep-water hydrothermal sources billions of years ago.
However, even when using the five criteria of life, namely: it requires energy, is connected by a membrane, is capable of storing genetic information, grows and is repeatedly reproduced, not everything on Earth is marked as “living” and “nonliving.” ’
Since we are currently locked at home because of this COVID-19 pandemic, let’s take viruses, for example. The virus falls into these categories, but it is not alive because it depends on other living cells for replication.
If our definition does not even work with the organisms that we have on OUR PLANET, it is likely that in a wider universe there will be numerous systems that also do not follow this definition.
Moreover, although there is such a huge variety of life forms on Earth, we can trace its origin from only one source: one random combination of events gave rise to this first cell or this first organism.
Numerous studies have shown that there are many alternative biochemistry and biology that could arise from the conditions of a young Earth. Researchers have suggested that if Martian life existed, it could metabolize carbon dioxide, just like Earth’s life forms do. However, this concept did not work, probably because they were especially looking for a life that metabolized carbon, like life on OUR PLANET.
Our definition of life is extremely imperfect, because it is based on the limited evidence we have about the infinitely large Universe. As far as we know, the Earth is the only “living” planet, and that is why we assume that our path to life is the only path.
NASA’s definition of life is worthy when used to establish what living things mean on Earth, as it covers most of the basics. However, any concept of life, as it applies to aliens, should be unlimited, and it should not make any assumptions about other life systems simply because it worked in our earthly installation to search for a copy of earthly life.
The universe is infinite, and therefore our concept of “alien” life must also be open.