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Life could have begun in an interstellar gas cloud
🕑 Added 2023-12-22 16:00:06 +0000 UTC[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.
Comments
Spot on! Panspermia and that research paper simply don't answer the question "how did life begin", they just push it off, as Sabine notes. There is evidence, although I can't find any right now, that lipid shells form normally and such a shell could have entrapped a set of chemicals, such as a set of self-replicating molecules and other molecular machines necessary for proto-life, a bit more than viruses have as they need cells, to start life. I doubt that space could provide the environment for any ongoing chemical reactions that are part of living cells.
How to define life? The german sience communicator Hoimar v. Ditfurth defined it in his book "Der Geist fiel nicht vom Himmel" (Mind didn´t fall down from heaven) as an act of demarcation from the environment. I always figured that very helpful. According to that, biological life began, when self reproducing chemical systems locked themselves behind a cell membrane. But can this work in an environment without any athmospheric pressure? My biological expertise says "No".
Rad, it's rather hard to figure out if something can be figured out before it has been figured out. It is my understanding that, at least for now, there are not known for sure places besides Earth where terrestrial life may survive for long without heavy technological assist. The Sun will heat-sterilize our planet, as it continues to brighten, in some 0.5 or in 1 to 1.5 billion years (depending whom one asks) first evaporating the oceans and stating a runaway climate warming that would take out all the water, turning Earth into a Venus analogue, even long before entering the red giant phase: https://www.science.org/content/article/earth-wont-die-soon-thought Mars and the bigger Galilean Moons, with plenty of space for life to exist, if conditions were right, will warm up as the habitable zone move outwards, but low gravity might make long-term all terrestrial animal life unhealthy and short, as it would all forms of life the cosmic radiation with no strong magnetic field protection, no proper atmosphere as a secondary shield, etc. If those moons' ice-crusts were to melt, perhaps terrestrial aquatic life might survive there if there truly are deep water oceans below the ice, warmed also by the energy of Jupiter tides. In one billion years of further evolution, we might have become aquatic ourselves to escape the heat of the Sun, if we are still around.
Rad Antonov
If we wanted to ensure some life from Earth survived the Sun’s red giant phase, could we figure out how to migrate organisms off the planet to another celestial body or even beyond the solar system? Is it conceivable that another civilization may have tackled the problem long before us? Not that it answers how life began but maybe there’s motivation to spread it once it starts.
So are we all aliens, both legal and illegal? And stromatolites maybe old, but they are still around and doing just fine. I do find it hard to believe that in those clouds, that are "dense" compared to the hard vacuum that most of space consist of, besides some fancy ribbons of some luminous stuff that probably is not very important in the larger scheme of things (just important enough that astrophysics is actually a thing that gets money to people like Tracey to subsist and forge on) and at temperatures cold enough to liquify hydrogen in practically a vacuum (*), there could be something out there organized enough to be a living, reproducing thing, is just *this* close to being completely unbelievable. For example, if some kind of life appeared and endured in such clouds, what would make it fit to survive and multiply under the utterly different conditions on Earth? "Panspermia" used to be in the realm of crackpottery until not so long (and it would seem has only half-emerged from it). But it has been gaining respectability, because why not? In fact, it is a fascinating idea. But until now, it has been about life carried around by meteoroids propelled off, by either volcanic explosions, or by collisions of planets with big asteroids, from those planets, where until then had been just rocks sitting unremarkably on the ground, but now carrying as passengers some microorganisms that had been living on this rock minding their business until propelled into interstellar space. Where, as it turned out, were of the kind that can live almost forever without anything to eat, drink, or breathe, and that also likes to shower in cosmic rays. That seems considerably more deserving of consideration, based on some meteorite evidence, the existence of extremophile bacteria in our world with some of those properties, and on our ignorance of where, when and how life actually got going on Earth. (*) [Emphasis is mine] In 1885, Zygmunt Florenty Wróblewski published hydrogen's [phase-diagram's] **critical temperature as 33 K (−240.2 °C; −400.3 °F); critical pressure, 13.3 standard atmospheres (195 psi); and boiling point, 23 K (−250.2 °C; −418.3 °F)**. https://en.wikipedia.org/wiki/Liquid_hydrogen
