The universe may be teeming with the molecules needed for life, a new study finds. The results come from the most comprehensive maps ever made of the types and locations of chemicals in the gas and dust surrounding newborn stars.
Stars spring from enormous clouds of gas and dust, which collapse under their own weight into disk-like structures. The centers of these disks heat up through friction and increased pressure until they ignite into fusion-powered stars, while the surrounding matter slowly clumps together into ever-larger chunks.
"We have known for some time that planets form in disks around young stars and that these disks contain molecules of interest for predicting the future compositions of planets," Karin Öberg, an astrochemist at Harvard University in Cambridge, Massachusetts, told Live Science.
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A few years ago, Öberg and her colleagues decided to use the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope in Chile that sees in the radio part of the electromagnetic spectrum, as a part of the Molecules with ALMA at Planet-forming Scales (MAPS) program. Because of their shapes and the bonds inside them, different chemicals vibrate in unique ways, producing telltale signatures that ALMA can capture, according to ALMA scientists.
The team looked at five protoplanetary disks, all between 1 million and 10 million years old, within a few hundred light-years of Earth. "That means they are in an actively planet-forming epoch," Öberg said.
MAPS determines not only the specific molecules in protoplanetary disks but also their locations. "Planets can form at many different distances from the star," Öberg said, so it's important to know what chemicals are available in each location to build these future planets.
An astounding 20 papers from this extensive mapping project are being published in a special future issue of The Astrophysical Journal Supplement Series; the first of these papers was made available on the preprint server arXiv on Sept. 15.
"What's so awesome is that there are several pieces rather than one big answer," Öberg said. "I think all 20 papers provide some different piece of the puzzle."
One of the most exciting findings for her was the abundance and distribution of a class of molecules known as cyanides. The simplest member of this family, hydrogen cyanide, is typically considered a poison, though many theories for the origin of life include a major role for this chemical class, she said.
"Seeing them in large abundance means planets are forming in the kind of soup we'd like to see" in order to fuel the emergence of life, Öberg added.
Cyanides also tended to be concentrated toward the inner parts and midplanes of the disks studied by MAPS — exactly where planets are expected to arise, she said.
Such molecules could form only in a low-oxygen environment with lots of carbon, Öberg added. This suggests that planets will be born with carbon-rich atmospheres, another point in favor of living things, since carbon is the basis of organic chemistry.
The results show that at least some of the organic building blocks of life are probably available in other stellar systems, but that doesn't necessarily make it more likely for humanity to find living organisms elsewhere.
"It's promising from an origin-of-life point of view," Öberg said. "But there's still a lot of work to do."
Living creatures would have needed a certain subset of chemicals in specific amounts in order to arise spontaneously, and scientists have yet to agree on what that recipe for life was.
There has been a lot of past effort into understanding the chemistry in the clouds that give rise to stars, as well as into analyzing the molecules in asteroids and comets, which can contain information about later periods of planetary formation, said Kathrin Altwegg, a planetary scientist at the University of Bern in Switzerland who was not involved in the new work.
"But there was one stage missing," Altwegg told Live Science — the stage that determined the chemistry in protoplanetary disks, and the results from this project are now helping to fill in unexplored details.
The findings also imply that a great deal of complex chemical formation already takes place prior to the birth of stars and planets, suggesting that these molecules come from interstellar clouds and are, therefore, widespread in space, she added.
Originally published in Live Science.
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Adam Mann is a freelance journalist with over a decade of experience, specializing in astronomy and physics stories. He has a bachelor's degree in astrophysics from UC Berkeley. His work has appeared in the New Yorker, New York Times, National Geographic, Wall Street Journal, Wired, Nature, Science, and many other places. He lives in Oakland, California, where he enjoys riding his bike.
By Kiley Price