Gary sent in the link to https://phys.org/news/2021-04-line-fuzzier-asteroids-comets-similar.html … space is filled with interplanetary dust and the Earth constantly collects it as it orbits around the sun. These dust particles are leading scientists to revise their thinking on the concepts of asteroids and comets. Enough to reconstruct the earlier history of the solar system. Whilst meteorites that fall to earth amount to 5 or 6 tones a year, when it comes to the dust penetrating the atmosphere, the number leaps to 40,000 tons annually. Using infrared spectrometry scientists have found a lot of this dust includes organic polymers, rich in hydro carbons and such elements as nitrogen and oxygen, and even deuterium [heavy water]. The presence of these compounds is leading to a change in outlook. Is there much difference between the make up of asteroids and that of comets?