SPHEREx will be a game changer in resolving long-standing questions about the amount and evolution of key biogenic molecules (H2O, CO, CO2, and CH3OH) throughout all phases of star and planetary formation.
In the early stages of star and planet formation (figure at left), the vast majority (99%) of molecules like water, carbon monoxide, and other volatile species are thought to exist in the solid phase, as ices. So in order to measure the amounts of these molecules in young systems, and to answer basic questions about whereand when they formed, they need to be detected via absorption spectroscopy. In this approach, nascent systems are seen in projection against bright background stars, and the ices generate absorptions (dips) in their spectra (figure below) from which their relative abundances can be measured.
Presently, there are only some 200 absorption spectra of ices in existence, hampering our ability to understand their formation and evolution. Fortunately, SPHEREx will increase the number of such spectra by orders of magnitude, by surveying young stellar systems of all kinds (young stellar objects, protoplanetary disks, and molecular clouds) throughout the Milky Way. Thus, we will understand for the first time, in a statistically significant way, how ice content correlates with cloud density, internal temperature, presence or absence of embedded sources, external UV and X-ray radiation, elemental abundances (e.g., C/O ratio), gas-phase composition, and cosmic-ray ionization rate.