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Scientists have long wondered how the complex molecules needed for life could be created around the chaotic and violent environment of the sun in its youth.
A family of meteorites called “chondrites” are theorized to have delivered the right stuff for life to Earth. But the question is, how did complex organic molecules containing elements like carbon, nitrogen and oxygen come to be sealed in the meteorites in the first place?
New research suggests that so-called “dust traps” in swirling disks of material around infant stars may be the “hot spot” for the formation of these macromolecules, the essential building blocks of life. Here, intense starlight from the young central star could irradiate the accumulated ice and dust to form carbon-containing macromolecules in a relatively quick few decades.
This would mean that the macromolecules could already be present when planets form more planets, or they could be sealed in asteroids in the form of small pebbles. These asteroids could then be broken down by repeated collisions in space, creating smaller bodies. Some of these may have come to Earth in the form of meteorites.
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“It is incredible to discover a crucial new role of dust traps in the formation of macromolecular materials that the planets may need to host life,” said team member Paola Pinilla from the Mullard Space Science Laboratory at University College London by Space.com. “Dust traps are favorable regions for the growth of dust particles into pebbles and planetesimals, which are the building blocks of planets.”
Pinilla explained that very small particles can be continuously recreated and replenished in these regions through continuous destructive collisions. These tiny micron-sized grains can easily be lifted into the upper layers of the flattened cloud of star-forming material that surrounds an infant star, known as a protoplanetary disk.
Once here, Pinilla said these particles can receive the right amount of radiation from their infant star to convert these tiny icy particles into complex macromolecular matter.
Replicating the early days of the solar system in the lab
Stars like the sun are born when dense patches form in massive clouds of interstellar gas and dust. Initially a protostar, the infant body collects material from what is left of its birth cloud, accumulating the mass needed to fuel nuclear fusion of hydrogen into helium in its core. This is the process that defines the “main sequence” of a star’s life, which lasts about 10 billion years for a star around the mass of the sun.
This young star is surrounded by a protoplanetary disk, material that was not used during its creation and rise to the main sequence. As the name suggests, plants form from this material and within the disc, but it also accounts for the origin of comets and asteroids.
Our solar system went through this process of creation about 4.5 billion years ago.
Previous research in laboratories here on Earth has shown that when these protoplanetary disks are irradiated with starlight, complex molecules of hundreds of atoms can form within them. These molecules are mostly made of carbon and are similar to black soot or graphene.
Dust traps in protoplanetary disks are high-pressure sites where the movement of molecules slows down, and dust grains and ice can accumulate. The slower speeds in these areas can allow grains to grow and, for the most part, avoid collisions that cause fragmentation. This means that they may be necessary for the formation of planets.
The team wanted to know if the radiation that the starlight brings to these areas could form complex macromolecules, and used computer modeling to test this idea. The model was based on observational data collected by the Atacama Large Millimeter/Sub-millimeter Array (ALMA), a series of 66 radio telescopes in northern Chile.
“Our research is a unique combination of astrochemistry, observations with ALMA, laboratory work, dust evolution, and the study of meteorites from our solar system,” said team member Nienke van der Marel from Leiden University. “It’s really cool that we can now use a model based on observation to explain how large molecules can form.”
The model showed the team that creating macromolecules in dust traps is a feasible idea.
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“We expected this result, of course, but it was a big surprise that it was so clear,” said team leader Niels Ligterink from the University of Bern. “I hope that colleagues will pay more attention to the effect of heavy radiation on complex chemical processes. Most researchers focus on relatively small organic molecules of a few dozen atoms in size, although there are mostly large macromolecules in the chondrites. “
“In the near future, we look forward to testing these models with more experiments and laboratory observations using powerful telescopes like the Atacama Large Millimeter Array (ALMA),” said Pinilla.
The team’s research was published on Tuesday (July 30) in the journal Nature Astronomy.
