We’ve long known from observations that complex atoms, including chlorofluorocarbons and polycyclic hydrocarbons, can be found in space. How they get there has been challenging to explain, but new work from the Max Planck Institute for Astronomy has sought to recreate in a lab what happens in space, and they are starting to succeed.  

Dust grains have been thought to be an onion-like structure, with a core of complex chemistry entombed in an icy shell. Left alone, the molecules might slowly grow through collisions, but would otherwise stay constant in their composition and structure. The thing is, dust is never really left alone when it’s in space. Dust molecules are regularly bombarded with cosmic rays, random atoms, and the ionizing ultraviolet light of our Sun. All these factors allow chemistry to take place – if the interactions make it through the icy shell – and allow for new and ever more complex atoms to slowly develop. 

It turns out our thinking on the structure of dust may be wrong. Experimental work by Alexey Potapov and his research team has determined the ices are thin enough that they may pose no real barrier. To quote from the press release, during the experiment: a laser is pointed at a graphite specimen, eroding (ablating) minute particles from the surface, mere nanometers across (where one nanometer is one-billionth of a meter). … Instead of grains completely covered with several layers solid ice (water ice, or carbon monoxide ice) like an onion, the dust grains they produced in the laboratory, staying as closely as possible to realistic deep-space conditions, were extended, many-tendrilled shapes – fluffy networks of dust and ice.

This shape gave them a hundred times the surface area we’d see in simpler structure, and allow more room for chemistry. This is a revelation and reminds us that the universe is far more creative in how it does things than our models often account for.

More Information

Max Planck Institute for Astronomy press release 

 “Ice Coverage of Dust Grains in Cold Astrophysical Environments,” Alexey Potapov, Cornelia Jäger & Thomas Henning, 2020 June 5, Physical Review Letters (Preprint on arxiv.org)