How likely is it that Earth-like origins of life will occur elsewhere?
Is life unique to Earth, or is it common in our galaxy? Retired astrophysicist Daniel Whitmill argues that Earth-like origins of life in rocky worlds similar to ours should be prevalent throughout the Milky Way. Image credit: NASA/ JPL-Caltech/ R. Hurt (SSC-Caltech)
We all know that life on Earth originated 3.7 billion years ago, but we still don't know exactly how life came to be. At the same time, we know almost nothing about life in other rocky worlds, even those that may be similar to Earth. Is life born by coincidence, or is it a common phenomenon, or is it something in between? Scientists debate the topic of "biogenesis", the idea that life arises from non-living materials. If this can happen on Earth, can it happen on other planets as well? A new paper by retired astrophysicist Daniel Whitmill at the University of Arkansas argues that it can happen. On September 23, 2022, Whitmere published his new peer-reviewed paper in the International Journal of Astrobiology.
The origin of life and our own existence
Basically, the paper is a refutation of the assertion of Australian-born astrophysicist Brandon Carter. Carter asserts that our own existence restricts our observation of other worlds where life may exist. "Actually, we exist because the origin of life did happen on this planet," he said. But - because so far we can only use our own planet as an example - it is impossible for us to determine how likely it is that life will appear elsewhere. Carter said that the Earth cannot yet be considered "typical...... Because there is no known set of terrestrial planets to compare with.
How likely is it that Earth-like origins of life appeared elsewhere?
Scientists tend to be conservative. They always guess whether something exists when they have definite evidence in their hands. As a result, many scientists seem to have accepted Carter's theory. But Daniel Whitmill didn't accept it. He thinks Carter's logic is wrong.
He points to what philosophers call the problem of old evidence. This philosophical question deals with what happens when a theory or hypothesis is updated and new evidence emerges. Whitmill argues that essentially Carter fails to take into account the role that long cosmic time scales play in the universe, for example, the length of time it takes for life to appear on a planet. Whitmill wrote: ... Observations of life on Earth are not neutral enough, but it is relatively easy to prove the origin of life on terrestrial planets. I... An independent time-scale argument is given, which quantifies the prior probability, so that it can be inferred that the time scale of biological origin is smaller than that of planetary habitability, so it is not uncommon for biological origin to occur on terrestrial planets.
This artist's image shows a super-Earth planet named GJ 1061d. Photo credit: ESO/ M. Kornmesser/ NASA.
Conceive analogies
Interestingly, Whitmill uses his own birth and existence as an argument against Carter's theory.
He wrote: Some people may argue, such as Carter, that I exist whether my ideas are difficult or easy, and therefore my existence alone cannot infer whether my ideas are difficult or easy.
He said: The concept about me (origin) can happen when my parents are using contraception (difficult to conceive = CH) or it can happen when they are not using contraception (easy to conceive = CE). Given the evidence of my existence, what is the probability of hypothetical H=CE?
His own concept is an example of old evidence, Whitmill writes: My own existence, however, is an old evidence, and must be treated as such. When this is done, the conclusion is that it is more likely that my appearance is easy. The same is true for the concept of biological origin. The existence of life on Earth is old evidence, just as in the conceptual analogy, the probability of easy origin of organisms is much higher.
Whitmere's argument is simple: the very existence of life on Earth itself is relevant to the question of whether life exists elsewhere. Whitmill asserts that, at least in theory, the existence of life on Earth enhances the possibility of life elsewhere.
New discoveries related to the origin of terrestrial life
A little later in September, I wrote about some new discoveries that added to the accumulation of evidence that could prove that life did exist elsewhere. In other words – from oceanic moons like Europa and Enclados, to the latest understanding of organic matter and ancient habitable conditions on Mars – conditions for life seem to abound, even in our own solar system. Beyond the vastness of the Milky Way, astronomers have discovered thousands of exoplanets. So we know that other solar systems exist as well. And, for me, as I write about these findings, the likelihood that life exists somewhere seems quite high.
Here's another example from the exoplanetary realm. There is new research suggesting that some (or many) unhabitable super-Earths exist as water worlds, but they may have the potential to be more habitable than Earth. Some are even completely covered in water.
Whitmill and Carter's methodology—a philosophical methodology—on the question of life in other worlds—is interesting. But while philosophers question the question, scientific discoveries are still advancing. Many scientists believe that we are close to finding the first conclusive evidence of extraterrestrial life. Some think this will happen in the next decade, or two, or even sooner.
If Whitmere is right, the first contact was undoubtedly very exciting.
BY:Paul Scott Andersonand
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