Theoretical origin of life: space is filled with organics (Introduction)

by David Turell , Wednesday, November 13, 2024, 18:07 (10 days ago) @ David Turell

All sorts of compounds have been found:

https://www.quantamagazine.org/the-cosmos-teems-with-complex-organic-molecules-20241113/

"The Rosetta mission and others have shown just how ubiquitous organic molecules are in space, too.

“'Rosetta really changed the view,” said Nora Hänni(opens a new tab), a chemist at the University of Bern who has been analyzing data from the probe. When Hänni and her colleagues processed just one day’s worth of the probe’s data in 2022, they uncovered(opens a new tab) 44 different organic molecules. Some were very complex, containing 20 atoms or more. Rosetta caught whiffs of glycine(opens a new tab), one of the amino acid building blocks of proteins. And more recently, Hänni used Rosetta data to identify dimethyl sulfide(opens a new tab) — a gas that, on Earth, is only known to be produced by living organisms.

"What Rosetta did for comets, Japan’s Hayabusa2 and NASA’s Osiris-Rex are doing for asteroids. In 2020 and 2023, respectively, the two missions scooped up samples of the asteroids Bennu and Ryugu and returned the samples to Earth. Scientists have been sifting through the material ever since, and they find that both asteroids sport plenty of organic molecules. Ryugu alone contains at least 20,000 kinds(opens a new tab), including 15 different amino acids.

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"By sending probes to sample primordial comets and asteroids, peering into planet-forming disks with telescopes, and re-creating spacelike conditions in labs and computer models, scientists are uncovering the origins of complex organic molecules. Their findings indicate that planets like ours likely inherit much of their organic material from a time before the sun.

"Last year, researchers glimpsed the earliest known occurrence of organic chemistry in the universe. The James Webb Space Telescope observed a young galaxy, seeing it as it appeared just 1.5 billion years after the Big Bang, and detected polycyclic aromatic hydrocarbons(opens a new tab) — hefty molecules that look a bit like honeycombs. On Earth, they’re found in anything involving tar, from fossil fuels to wood smoke. In space, they’re components of asteroids — including those that fall to Earth as meteorites — and of interstellar dust.

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"There’s a second major formation pathway. As generations of stars have lived, died and spilled their innards into space, some of their carbon has ended up in molecular clouds — patches of space where motes of gas and dust crowd close enough together to block out light. Here, organic molecules form within the icy crusts of tiny dust grains. “You can build complexity without much going on in just a cold, dark cloud,” said Alice Booth(opens a new tab), an astronomer at Harvard.

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"The upshot, according to Booth, is that even billions of years before the sun was born, “you can form pretty complex molecules,” she said. “What we don’t really know is how all of that complexity at early times translates to later times.”

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"Only recently did scientists get their first glimpses of organic molecules within protoplanetary disks — the rotating frisbees of gas and dust that spin around newborn stars. “Every disk is a gold mine,” Öberg said. In one of these observations, Booth and her colleagues found abundant methanol(opens a new tab) within a nearby planet-forming disk. This methanol could only have formed on grains of carbon monoxide–rich ice, which would have filled the cold molecular cloud from which the protoplanetary disk came but would then have vaporized in the warm disk. So, Booth said, the methanol must have come from the cloud that predated the new star and its planets.

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"Researchers have wanted to computationally model the churn and tumble of disk material, but it’s so computationally costly to do so that “until we absolutely had to, we have sort of been avoiding those [studies],” Öberg said. That’s changing now. In 2024 a team of scientists including Booth published initial results of computer models showing(opens a new tab) that complex organics can form rapidly in protoplanetary disks. In particular, the molecules assemble in the same “dust traps” where planetesimals, the asteroid-size building blocks of planets, coalesce. The results provide a tantalizing link between the formation of organics and planets.

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"For decades, scientists have known that meteorites called chondrites, which originate from asteroids, contain a staggering diversity of organic molecules. The Murchison meteorite, which fell in Australia in 1969, contains more than 96 different amino acids. Life uses just 20 or so. Osiris-Rex and Hayabusa2 have confirmed that the asteroids Bennu and Ryugu are as complex as those meteorites. And at least some of this complexity seems to have arisen before the asteroids themselves: A preliminary analysis(opens a new tab) of the Bennu sample suggests it retained organic material, including polycyclic aromatic hydrocarbons, from the protoplanetary disk.

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"...as comets and asteroids reveal, the nonliving world is complex in its own right. Compounds thought to be biosignatures have been found on lifeless rocks, like the dimethyl sulfide Hänni’s team recently identified on 67P."

Comment: the non-living world is filled with organic molecules. Living matter was destined, but we just don't know how it happened