Planetary scientists have long held that the organic macromolecules making Earth hospitable to life originate from chondrites, primitive meteorites composed of aggregated pebbles. However, the process by which these pebbles acquired macromolecules remained unclear. Researchers from TU Delft and Leiden University, among others, now provide an explanation.

Combination of Dust Trap and Radiation
The researchers' model combines two observed phenomena. The first involves regions in the dust disk orbiting a young star where dust and ice accumulate, known as dust or ice traps. In these traps, icy dust is not static but moves vertically.

The second phenomenon is the heavy irradiation of simple ice mixtures by stellar light. Laboratory research shows that such irradiation can form very complex molecules, containing hundreds of atoms, primarily carbon. These molecules are comparable to black soot and graphene.

The researchers hypothesized that dust traps exposed to intense starlight could facilitate the formation of organic macromolecules. They developed a model to calculate various conditions to test this hypothesis.

The model revealed that under optimal conditions, macromolecules could form within just a few decades.

"We had hoped for this result, of course, but it was a nice surprise that it was so obvious," said principal investigator Niels Ligterink, who is currently at the University of Bern in Switzerland and will move to the Technical University of Delft (the Netherlands) in July. "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, while chondrites contain mostly large macromolecules."

"It's really super cool that we can now use an observation-based model to explain how large molecules can form," commented co-author Nienke van der Marel of Leiden University. Eleven years ago, she and her colleagues were the first to convincingly demonstrate the existence of dust traps, and she has been passionate about the subject ever since. "Our research is a unique combination of astrochemistry, observations with ALMA, laboratory work, dust evolution, and the study of meteorites from our solar system."

Future research will focus on how different types of dust traps respond to radiation and moving dust flows. This will enhance understanding of the potential for life around various types of exoplanets and stars.

Research Report:The rapid formation of macromolecules in irradiated ice of protoplanetary disk dust traps.

Related Links
Netherlands Research School for Astronomy
Stellar Chemistry, The Universe And All Within It