Mikko Tuomi

Here is a problem that has been quietly gnawing at astronomers for decades.

The standard approach to detecting #life on other worlds involves scanning #exoplanet #atmospheres for #oxygen, #methane, and #ozone, whose presence is difficult to explain without #biology.

It's a clever idea, but it carries a hidden flaw. That entire shopping list was written by studying Earth. It is, inevitably, a search for life like us.

The list of ways that #chemistry alone can accidentally mimic these #biosignature gases is growing faster than the list of new ways to detect life.

Each new false positive scenario demands even more information about the #planet to rule it out, and there is a genuine question about whether that information can ever be gathered exhaustively.

But there is a solution.

#Assembly theory doesn't ask what #molecules are present in an #atmosphere. Instead, it asks how hard they were to make.

Every molecule can be assigned an assembly index, a minimum number of construction steps required to build it from basic #chemical building blocks.

Simple molecules are easy to assemble by chance, but truly complex ones, requiring many sequential steps, don't arise without something doing a great deal of deliberate selection.

That something would then be life itself.

#astrobiology #astronomy
https://phys.org/news/2026-03-life.html

Paper by Walker et al. (2026): https://arxiv.org/abs/2603.11086

Life, but not as we know it

Here is a problem that has been quietly gnawing at astronomers for decades. The standard approach to detecting life on other worlds involves scanning exoplanet atmospheres for oxygen, methane, and ozone, whose presence is difficult to explain without biology. It's a clever idea, but it carries a hidden flaw. That entire shopping list was written by studying Earth. It is, inevitably, a search for life like us.

Phys.org
Mar 19 at 11:09pmWeb
Show threadZalasur 🐸🇺🇦1d ago

@mustapipa The main problem with that approach is that those complex molecules are very hard to detect with spectroscopy, our only method of detecting chemicals on other planets. The more complex the molecule, the more "muddied" the spectral lines.

Looking for the basic molecules is a way of narrowing down the list of potential planets that we can than look at in more detail for other non-chemical signatures.

Show threadMikko Tuomi1d ago
@zalasur Of course, but things can be learned without comprehensive solutions, too. Perhaps we only have to learn to live with uncertainty.
Show threadWelkin17h ago
@mustapipa
In a universe which is 13+ billion years old and more than 90+ billion light years across the chance of building such complex molecules without life playing a part is a real possibility if not a forgone conclusion.
I agree that life, like we know of, may not be the only possible outcome. Life may be silica based instead like us, which is carbon based.