One of science’s most important unsolved mysteries is the origin of life. The fact that life on Earth began 4.5 billion years ago, only a few hundred million years after the Solar System formed, and required multiple essential molecular components is one piece of this puzzle. How on earth did all these parts become readily available so quickly?
The idea that the components of life were brought to Earth from space is one possible explanation. The theory states that all of the organic molecules required for life are present in clouds of gas and dust that fill space.
These building blocks have in fact been seen by
astronomers in interstellar gas clouds. Amino acids, the building blocks of
proteins, and the mechanisms of life are visible to them. Additionally, they
are able to see the building blocks of ribonucleotides, which are molecules
that can store data as DNA.
However, molecules with the ability to form membranes that can cover and protect life’s molecules in compartments known as protocells are another vital component for life. All cells on Earth have membranes composed of molecules known as phospholipids. But no one has ever seen these up in space. Thus far.
Life’s precursors
Ethanolamine, an essential part of the most basic phospholipid, has been detected in space for the first time by Víctor Rivilla of the Spanish Astrobiology Centre in Madrid and associates. According to the discovery, the interstellar medium is full of all the building blocks of life. “This has important implications not only for theories of the origin of life on Earth, but also on other habitable planets and satellites anywhere in the Universe,” say the team.
By examining light from Sagittarius B2, an
interstellar cloud of gas and dust located 390 light years from the Milky Way’s
center, the team made their discovery. This area has long been recognized by
astronomers as a rich source of organic molecules, ice, and dust particles.
The chemical formula for ethanolamine is NH2CH2CH2OH. The group generated a simulation of the spectrum that this molecule should have at the low temperatures assumed to be present in the cloud. Next, they examined light that had gotten through the cloud for obvious proof of this spectrum, which they discovered.
Astronomers have discovered ethanolamine in meteorites, despite it having never been observed in space before. How it got there has been an issue of some debate with some researchers arguing it could only have formed through an unusual set of reactions on a parent asteroid.
The latest finding implies that ethanolamine is far
more common. On Earth, it takes the form of the hydrophilic head of
phospholipid molecules, which combine to form membranes inside cells.
“Ethanolamine could have been transferred from the proto-Solar nebula to
planetesimals and minor bodies of the Solar System, and thereafter to our
planet,” according to Rivilla and colleagues, who discovered it in interstellar
clouds. That might have caused cells to form in the prebiotic soup that our
earliest ancestors emerged from.
Radical notion
An even more radical theory is that protocell
formation in the interstellar medium itself could be facilitated by
ethanolamine. This is abundant in other prebiotic components that these
protocells would have naturally encapsulated, like water and amino acids. The
end product would be prebiotic goop in melting pots that are ready to be used
to seed the Earth or any other body that happens to pass by.
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