Space rocks reveal how early solar system separated rock from ice-rich dust

During the Solar System’s first million years, its earliest outer worlds appear to have formed from a carefully filtered mix of material, with heat-forged chondrules making up between 83% and 92% of their composition. In the young disc, aerodynamic sorting separated these rocky grains from fine matrix containing water ice and organic molecules, leaving the first planetesimals unusually poor in volatile-rich dust. According to the new study published in Nature Astronomy, titled ‘Planetesimal compositions governed by aerodynamic sorting from the onset of Solar System formation’, because many of these ancient bodies later melted, researchers turned to iron meteorites for chemical clues.