One of the most important molecules in your cell membranes was just discovered in an unexpected place: a dense cloud of dust and gas far away in space.
Astronomers spotted the telltale spectral signature of a molecule called ethanolamine in a molecular cloud near the center of our galaxy. Using data from the IRAM and Yerkes radio telescopes, a Spanish-led team of astronomers was able to draw out ethanolamine, an important component of cell walls.
The presence of this important life ingredient suggests that the building blocks of life actually form in interstellar space and may already have been part of the mix when planets and asteroids started forming in our solar system.
The study was Monday in the Proceedings of the National Academy of Sciences.
What’s new — Spectra of ethanolamine was spotted 100,000 light years away in a cold molecular cloud charmingly named G+0.693-0.027.
Astronomer Victor Rivilla of the Consejo Superior de Investigaciones Cientíıficas–Instituto Nacional de Tecnica Aeroespacial and his colleagues describe G+0.693-0.027 as “one of the most chemically rich reservoirs of molecules in the galaxy.”
- Slow collisions between masses of gas and dust triggered chemical reactions on the icy surfaces of dust grains.
- Those reactions gradually converted other, simpler combinations of nitrogen, hydrogen, oxygen, and carbon into ethanolamine.
"The fact that we are finding, in interstellar molecular clouds, key prebiotic precursors is telling us that the simplest chemical pieces needed for life are likely spread across the Galaxy," Rivilla tells Inverse. "This chemical feedstock will be available for the formation of new stars and planets, in which, under the right physical conditions, new forms of life might arise."
Astrochemist Sergio Ioppolo of Queen Mary University London, who was not involved in the study, calls these reactions "dark chemistry," because they happen in areas of space where stars haven't formed yet — such as cold, dark molecular clouds.
Here’s the background — While you probably don’t spend much time thinking about ethanolamine, your life depends on it. The membranes around your cells are made of complex molecules called phospholipids, packed together tightly enough to form a two-layered barrier that can keep cell material in and the outside world out.
Ethanolamine is part of the heads of those phospholipids: the end that forms the outer and inner surfaces of the cell membrane.
Under the right circumstances — such as underwater hydrothermal vents, where life on Earth may have gotten its start — simulations have shown that ethanolamine could help form an amino acid called glycine. Amino acids are the building blocks of proteins.
“Now, if the ingredients of life are spread across the Universe, it is also likely that life can emerge anywhere as soon as the conditions are favorable.”
Ethanolamine has previously been found in trace amounts in meteorites, though scientists weren’t sure if it was a primordial form or from the breakdown of other organics into the chemical. But the PNAS study suggests that dark molecular clouds, where no stars burn yet, are the perfect factory for complex organic molecules like ethanolamine. That’s because the surfaces of dust grains make a much better environment than open space for the necessary series of chemical reactions.
In another study earlier this year, Ioppolo and his colleagues found that the amino acid glycine could also form on dust grains in the interstellar medium, under conditions similar to those in molecular cloud G+0.693-0.027.
“Hence, the formation of [complex organic molecules] and other prebiotic species is likely to occur during the early stages of, or prior to, star formation,” Ioppolo tells Inverse. “They can then potentially survive the star formation process until their inclusion in planets and planetesimals, enriching the organic molecular diversity on the surface of primordial worlds across our galaxy, the Milky Way, and likely beyond that."
When Rivilla and his colleagues observed the distant reservoir of molecules in G+0.693-0.027 through radio telescopes, they saw that something in that molecular cloud was reflecting energy toward Earth in wavelengths that matched ethanolamine.
Why It Matters — Scientists studying the origins of life have struggled to figure out how some of the complex molecules needed to build even primitive cells could have formed from scratch in the environment that existed on Earth 4.2 billion years ago.
The discovery of ethanolamine in interstellar space suggests that some of the more complex ingredients for life might have arrived, partially pre-assembled, as part of what Rivilla calls the “chemical feedstock” of new stars and planets.
That’s a major clue about how life may have formed here on Earth, but it also suggests that life may have better odds of happening elsewhere than we’ve previously given it credit for. According to Ioppolo, the odds of prebiotic building blocks combining to kickstart life on any Earth-sized rocky planet in the habitable zone of its star should be about the same as Earth 4.5 billion years ago.
“Now, if the ingredients of life are spread across the Universe, it is also likely that life can emerge anywhere as soon as the conditions are favorable,” Ioppolo says. “Life is likely not an exception, but more like an extra step of the evolution of star formation regions in space.”
What’s Next — Understanding more about how the building blocks of life could form in interstellar space will require a combination of astronomy, computer models, and chemistry experiments in the lab.
For Rivilla and his colleagues, one important next step is to look for ethanolamine in other places. As Rivilla tells Inverse, “We have detected ethanolamine only towards a single molecular cloud in the center of our Galaxy. It is relatively abundant there, but we would like to know if this is also the case for other places in our Galaxy.” In particular, their search will focus on molecular clouds where new stars and planets and forming, to see if the ingredients of life turn up in a newborn solar system that might, one day, resemble ours.
Since ethanolamine is just one of those ingredients, Rivilla and his colleagues also have a grocery list of other chemicals they want to search for in interstellar space. Near the top of the list is a molecule called aminoacetaldehyde, whose name is a bit of a mouthful but which is one of the chemicals that help form ethanolamine, but is harder to detect in space.
“It is very likely that in the next few years, we will discover more and more molecules in space and understand more deeply the relation between dust, ice, and gas in space,” Ioppolo says. “This will be key to a better grasp of the physics and chemistry ruling the formation of stars and planets and the emergence of life in the Universe.”
Abstract — Cell membranes are a key element of life because they keep the genetic material and metabolic machinery together. All present cell membranes are made of phospholipids, yet the nature of the first membranes and the origin of phospholipids are still under debate. We report here the presence of ethanolamine in space, NH2CH2CH2OH, which forms the hydrophilic head of the simplest and second-most-abundant phospholipid in membranes. The molecular column density of ethanolamine in interstellar space is N = (1.51 ± 0.07) × 1013 cm−2 , implying a molecular abundance with respect to H2 of (0.9 − 1.4) × 10−10. Previous studies reported its presence in meteoritic material, but they suggested that it is synthesized in the meteorite itself by decomposition of amino acids. However, we find that the proportion of the molecule with respect to water in the interstellar medium is similar to the one found in the meteorite (10−6 ). These results indicate that ethanolamine forms efficiently in space and, if delivered onto early Earth, could have contributed to the assembling and early evolution of primitive membranes.