Life could have begun in an interstellar gas cloud (Patreon)

[This is a transcript with links to references.]

Scientists have long speculated that life didn’t begin on earth but in space. According to a new preprint, life could have come from intergalactic gas clouds, so let’s have a look.

The oldest confirmed traces of life are biostructures called stromatolites, that’s layers of rock which contain remains of single-celled organisms. These organisms are believed to have been either algae or some kind of bacteria. Scientists have dated them back to about 3 point 5 billion years.

Earth itself is about 4 point 5 4 billion years old, but when it formed it was really hot and no solid crust. Life back then wasn’t possible. But at the young age of about half a billion years, Earth had cooled enough for the surface to become partly solid. There were still frequent volcano eruptions, but most scientists believe that life emerged after the surface temperature had dropped below the temperature where water boils.

Back then, the Earth's atmosphere was very different from what it is today, with high levels of carbon dioxide and nitrogen, water vapour, and toxic gases that were released during volcanic activity. There was also still a lot of stuff flying around in the solar system, so there were frequent meteorite impacts.  Basically, a toxic atmosphere with frequent microaggressions.

Going by the available evidence, scientists place the origin of life between roughly 3 point 9 and 3 point 7 billion years in the past. But just how life began on earth is one of the big unsolved problems of science. Somehow, all this inert matter must have combined to self-replicating molecules that could adapt to their environment and, after some billions of years, achieve this pinnacle of evolution: YouTube. But just how did that happen? No one knows.

The first idea was that lightning strikes did it, going back to a now famous experiment by Stanley Miller and Harold Urey in 1952. They created a closed system from two glass flasks and filled it with gasses that they thought mimicked the early Earth's atmosphere. Then they added electric sparks to simulate lightning, which they believed to have been common on early Earth. A week later, they found that their flask contained several amino acids, the building blocks of proteins.

That got everyone very excited, and for a brief and glorious time scientists thought the problem had been solved. But then other researchers pointed out that the atmosphere on earth back then would have been different, so it couldn’t really have worked like this. Then again others said, maybe we’re misinterpreting some of the data, or it worked differently, maybe life emerged near underwater volcanoes, or in hydrothermal vents, or some vital ingredients came from meteorites, and so on.

If you think all of this sounds a little crazy, I won’t blame you, but there’s actually evidence to back up at least some of it. Scientists have indeed found life on Earth in some of the most unexpected places – from hydrothermal vents at the bottom of the ocean to the glaciers of Antarctica. Life, it seems, is unexpectedly robust and can survive in incredibly difficult circumstances. They’ve also found the building blocks of life, amino acids, inside of meteorites and even in outer space.

And this brings us to the idea that the first life on our planet arrived fully formed from outer space. It’s known as “panspermia”, and says that life originated elsewhere, either on another planet or indeed in outer space, rained down on earth from meteorites or dust, and found Earth to be a welcoming environment. Some even go so far to say that life was deliberately seeded by aliens to spread through the universe. And that brings us to the new paper.

In the new pre-print, a Chinese researcher looked at the possibility that life on Earth came from molecular clouds in space. Molecular clouds are dense clouds of gas and dust in interstellar space where new stars form -- and god knows what else. These clouds are believed to be mostly made of hydrogen, but we know from spectral analyses that many other chemical elements can form there, too. That makes these clouds good candidates for space-born life.

The author says that these molecular clouds could sustain life in the form of methanogenic bacteria. They are called that way because they generate methane. Some of the first forms of life on Earth have indeed been of this type. Furthermore, it’s so cold in these clouds that the hydrogen is liquid. This means it could be contained by cell membranes and the microbes could use it to transport molecules through the membranes.

The author also says there is enough carbon monoxide, carbon dioxide, and hydrogen in the clouds to keep the bacteria alive. The paper does not explain, however, how this life came about in the first place, just that some forms of life could have survived in those molecular clouds.

That sounds possible, but is it right? Well, more research is needed. Personally, I like the idea that we’re someone’s bio-experiment gone badly wrong.