text: Like biotic molecules, position specific isotope enrichments in abiotic molecules can reflect the source of chemical precursors and synthesis pathways. The energy for abiotic reactions can come from many different sources, which will affect fractionation. For instance, metal catalysts can speed up abiotic reactions. Reactions can be slowed down or sped up by different temperature and pressure conditions, which will affect the equilibrium constant or activation energy of reversible and irreversible reactions, respectively. 
  For example, carbon in the interstellar medium and solar nebula partition into distinct states based on thermodynamic favorability. Measuring site-specific isotope enrichments of carbon from organic molecules extracted from carbonaceous chondrites can elucidate where each carbon atom comes from, and how organic molecules can be synthesized abiotically. More broadly, these isotope enrichments can  provide information about physical processes in the region where the molecular precursors were formed, and where the molecule formed in the solar system (i.e., nucleosynthetic heterogeneity, mass independent fractionation, self-shielding, etc.).
  Another example of distinct site-specific fractionations in abiotic molecules is Fischer-Tropsch-type synthesis, which is thought to produce abiogenic hydrocarbon chains. Through this reaction mechanism, site enrichments of carbon would deplete as carbon chain length increases, and be distinct from site-specific enrichments of hydrocarbons of biological origins.