 99% of the mass of the circumstellar disk is in the form of gas, with just 1% in the form of dust. The solid dust has little effect on the star formation, but it's key to planetary formation. Dust is the only solid grains available for growing planets. Dust itself cannot be formed directly from purely gaseous material at the low densities found in interstellar molecular clouds. Instead, solid grains are known to form in planetary nebula, supernova, and in the outer atmospheres of cool supergiant stars. The dust in the interstellar medium extinguishes light from stars by absorption and scattering. The scattering leads to emissions of their own. Comparing dusty clouds to non-dusty clouds using spectral absorption and emission lines shows that almost all the iron, magnesium, silicon, much of the carbon, and some of the oxygen and nitrogen are contained in the dust. This makeup is similar to the terrestrial, amorphous, non-crystalline rocks. If the temperature permits, they are surrounded by a mantle of water ice. The original dust grains in the cloud are no longer available for direct observation. But to this day, there are similar objects in our solar system called interplanetary dust particles. They are being collected in the thermosphere by the International Space Station. Here's an electron microscope view of one of them. It's 10 micrometers in length. That's around 100 times larger than interstellar dust. NASA also uses high-flying aircraft to collect dust at high altitudes before it gets close enough to the surface to mix with earth elements. In 2018, a team of scientists from the University of Hawaii examined this dust with electron microscopes. They mapped the element distributions and discovered that these glassy grains are made up of sub grains that aggregated together prior to the formation of the comet, the interplanetary dust particles came from. These represented samples of the early interstellar dust.