The science approaches this topic in various ways. A geneticist who works with organisms and their genomes has a very different view on what is life than an astrophysicist, for instance, who has a broader, expansive, and universal view on the same matter. The definitions of life based on Earth means that what sentient and conscious alien life might resemble almost always reflect humankind.
Life on Earth
However, a lot about the way life arose to Earth is still unknown. Researchers still don’t know whether DNA or RNA was the first genetic material, or whether life appeared from what is known as the primordial soup. This ‘soup’ was believed to be a mix of organic and inorganic molecules found on the surface of Earth, or it came from energy moving from deep-sea hydrothermal vents billions of years ago.
However, even using the five criteria for life; namely, it requires energy, is bound by a membrane, is able to store genetic information, and grows and replicates numerous times, not everything on Earth is labeled as ‘living’ and ‘non-living.’
Since we’re currently locked at home because of this COVID-19 pandemic, let’s take, for example, viruses. A virus falls within these categories, but it is not alive because it depends on other living cells in order to replicate.
A More Open Concept
Moreover, although there is such huge diversity of life on Earth, we might only ever trace life back to one origin: a single random combination of events birthed that first cell or that first organism ever.
Numerous studies have recognized that there are a lot of alternative biochemistries and biologies that could have emerged from the conditions of young Earth. Researchers speculated that if there was Martian life, it would metabolize the radio-categorized species and generate radio-labeled carbon dioxide, similar to the manner Earth life forms would. However, the concept did not work, probably because they were particularly looking for life that metabolized carbon, just as life on our planet does.
Our definition of life is hugely defective because it is founded on the restricted evidence we have of an infinitely large Universe. As far as we know, Earth is the only ‘living’ planet, and that is why we assume that our way towards life is the only path.
NASA’s definition of life is a decent one when used to establish what living things mean on Earth as it covers most basics. However, any concept of life as it applies to aliens has to be limitless, and it should not make any speculations about other life systems simply because in our setup worked. The Universe is infinite, and therefore, our concept of ‘alien’ life has to be an open slate as well.