Their formation may be associated with shock waves.
The ALMA snapshot shows similar regions. They are located in a dust disk surrounding two very young stars. The colors indicate the temperature distribution: brighter shades correspond to a higher temperature.
Shock waves may help enrich the gas at the early stages of the formation of the circumstellar disk with complex organic molecules, which can later become part of the substance of newborn planets. High temperatures associated with shock waves can also affect the process of dust particles sticking together. Namely, it also depends on how early planetary nuclei can begin to form in the disk.
