How can spectroscopy reveal so much about asteroids and comets?
Spectroscopy is the process where we point a telescope at an object in space and pass the light from that object through an instrument, which in turn, spreads the light out. Light is arranged by wavelength into a pattern called a spectrum. We collect spectra with detectors that translate this into data that we can then go on to analyse.
It is known that asteroids are made primarily of rock, while comets are a mix of ices and rock. This is why comets are commonly referred to as ‘dirty snowballs’. Those rocks and ices absorb and emit light at specific wavelengths, making a spectral fingerprint. By studying the spectrum of an asteroid or comet, we can identify the fingerprints associated with different types of rock and ices. We then know what the asteroid or comet is made out of without having to collect a sample. The composition of asteroids and comets can tell us about how and where they formed, and how they’ve changed over the age of the Solar System. We can use that information to study one particular small body in detail or how populations of small bodies are distributed throughout the Solar System.