EarthSky | What is the likelihood of an Earth-like origin of life elsewhere?

We know that life originated on Earth about 3.7 billion years ago. But we still don’t understand exactly how life came about. Likewise, we know little or nothing of life on other rocky worlds, even those that might look like Earth. Is life a rare event or is it common? Or somewhere in between? Scientists debate the subject of abiogenesis, the idea of ​​life arising from non-living materials. If it can happen on Earth, can it also happen elsewhere? A new paper by retired astrophysicist Daniel Whitmire of the University of Arkansas argues that it is possible.

Whitmire has published her new peer-reviewed article in the International Journal of Astrobiology September 23, 2022.

Abiogenesis and our own existence

Basically, the article is a counter-argument to the opinion of Brandon Carter, an Australian-born astrophysicist. Carter asserts that our own existence constrained our observations of other worlds where life might exist. What does he mean? Essentially, he says, we ourselves happen to exist on a planet where abiogenesis has occurred. But – since we only have our own planet as an example so far – it is impossible for us to determine the probability that life has emerged elsewhere.

Carter says Earth can’t yet be considered “typical”…because there is no known set of Earth-like planets to compare it to.

What is the likelihood of an Earth-like origin of life elsewhere?

Scientists tend to be conservative. They don’t like to speculate that something exists until they have the evidence. So many scientists seem to accept Carter’s theory. But Daniel Whitmire does not accept it. He argues that Carter is using faulty logic.

It highlights what philosophers call the problem of old evidence. This philosophical problem concerns what happens when a theory or a hypothesis is updated, following the appearance of new evidence. Whitmire is essentially saying that Carter doesn’t take into account the long cosmic time scales at play in the universe, for example, the time it takes for life to emerge on a planet. Whitmire writes:

… The observation of life on Earth is not neutral, but the proof that abiogenesis on Earth-like planets is relatively easy. I…give an independent timescale argument that quantifies prior probabilities, leading to the conclusion that the timescale of abiogenesis is less than the timescale of planetary habitability and that, therefore, the occurrence of abiogenesis on Earth-like planets is not uncommon.

The design analogy

Interestingly, Whitmire uses her own birth and existence as an argument against Carter’s theory. He writes:

One could argue, like Carter, that I exist regardless of whether my conception was difficult or easy, and therefore nothing can be inferred as to whether my conception was difficult or easy from my existence alone.

And he says :

My conception (origin) could have happened if my parents used contraception (hard conception = CH) or if they did not use contraception (easy conception = CE). What is the probability of the hypothesis H = CE, given the evidence that I exist?

His own design is an example of ancient evidence, Whitmire said:

However, my existence is old evidence and should be treated as such. When this is done, the conclusion is that it is much more likely that my conception was easy. In the case of interest for abiogenesis, it is the same thing. The existence of life on Earth is ancient evidence, and just like in the analogy of conception, the likelihood of abiogenesis being easy is much more likely.

Whitmire’s view is simply that the existence of life on Earth is, in itself, significant to the question of whether life exists elsewhere. In theory, at least – argues Whitmire – the presence of life on Earth reinforces the possibility of life elsewhere.

New discoveries linked to an Earth-like origin of life

At the end of September, I wrote about recent discoveries that add to the mounting evidence that life does indeed exist elsewhere. In other words – from oceanic moons like Europa and Enceladus to the latest insights into organic matter and ancient habitable conditions on Mars – the conditions for life seem to abound, even here in our own solar system. In the vast Milky Way galaxy beyond, astronomers have discovered several thousand exoplanets. So we know that other solar systems exist. And, to me, as I write about these discoveries, the odds seem pretty good that life is out there somewhere.

Here is another example from the realm of exoplanets. New studies suggest that some (or more) super-Earths could exist as aquatic worlds that are not only habitable, but potentially even After habitable than Earth. Some may even be completely covered by oceans.

Whitmire and Carter’s approach – a philosophical approach – to the question of life on other worlds is interesting. But, as philosophers discuss the matter, the pace of scientific discovery continues. And many scientists believe that we are now on the verge of finding our first definitive proof of extraterrestrial life. Some think it will happen in the next decade or two…or sooner.

If Whitmire is right, this first discovery will be truly exciting.

Conclusion: Retired astrophysicist Daniel Whitmire says an Earth-like origin of life (abiogenesis) is likely very likely on other rocky worlds similar to ours.

Source: Abiogenesis: Carter’s Argument Reconsidered

Via the University of Arkansas