Vol. 596
In section 10. Planets and planetary systems

Dust particles flux and size distribution in the coma of 67P/Churyumov-Gerasimenko measured in-situ by the COSIMA instrument on board Rosetta

Merouane et al. analyze the particles collected in the coma of comet 67P between 3.5 au and 1.9 au on its way to perihelion by the COSIMA instrument on board ROSETTA. The size distributions that they derive will be crucial to inform us about the mechanisms producing these particles. The authors also provide evidence for an unexpected dichotomy: Approximately half of the large particles collected are porous aggregates that appear to be very similar to chondritic porous interplanetary dust particules and can reach millimeter sizes. The other half consists of compact particles with sizes ranging from about 10 to 100 microns. How this dichotomy was generated is a mystery and may be an important piece of the puzzle to understand the formation and evolution of comets.