Molecular contamination of optical surfaces, thermal control components, or other spacecraft components can lead to end-of-life performance degradation. In particular, exposure to vacuum ultraviolet (VUV) radiation is known to enhance contaminant deposition rates. Known mechanisms for photodeposition and photopolymerization of contaminants are here reviewed to provide insight into the underlying chemistry and reaction mechanisms. Previous works have shown that many variables influence the rate of contaminant uptake, including temperature, VUV energy, and material properties of both the contaminant molecules and the substrate. Additionally, the photochemistries of three common spacecraft outgassing contaminants (DOP, BPA, and DC 704) are discussed to provide insight into future modeling efforts.