The first small objects would have orbits of many angles and shapes and would approach large planets like Jupiter or Neptune from many different angles. So they would get scattered in every direction. This means that while nearly everything in the solar system goes round in the same direction, because of the original solar nebula's rotation, half of the comets circulate the other way. This is taken as further proof that the Oort Cloud objects represent a set of random scattering events, which would result in an even spherical distribution. The content of comets can be investigated just like that of stars.
Astronomers use spectroscopes, which separate different wavelengths of light from a single source.
Of course meteorites also provide samples of the rocky and metallic parts of comets as well. The substances found in comets and their proportions are one things that helped scientists determine that comets were created early in the solar system. Besides water and carbon dioxide , other organic substances like formaldehyde and methane are frequently detected in comets by their spectral signatures in the light from the plasma tail and coma . These substances freeze at temperatures much lower than water. This module links the compounds in the nucleus with the appearance of the ion plasma tails as well.