Parent Molecule, Comet
A parent molecule is a molecule directly released from cometary material, e.g., by sublimation of cometary ices. It contrasts with daughter molecules, which are their degradation products. Historically, daughter molecules (CN, C2, C3, CH, OH, NH…) were first observed in cometary spectra from their electronic bands in the visible and the nature of their parents was the subject of speculations. Parent molecules (H2O, CO, CO2, NH3, HCN, hydrocarbons…) were definitely identified more recently from their vibrational bands and rotational lines in the infrared and radio spectral domains, as well as from in situ mass spectroscopy.