Hydrogen isotopic exchange kinetics between organic matter and water: Implications for chemical evolution during meteorite parent body processing

Abstract The large variations in hydrogen isotope ratios found insoluble organic matter (IOM) chondritic meteorites may be attributed to isotopic exchange between IOM and water during aqueous alteration. We conducted D–H experiments (1) synthesis of simulant (hereafter called analog, COA) from formaldehyde, glycolaldehyde, ammonia with water, (2) the synthesized COA a secondary reservoir water. changes D/H obtained by infrared spectra suggest that most is derived synthesis. further investigated kinetics D‐rich D‐poor as well opposite case, To help assess understanding kinetics, two‐dimensional imaging using microscope revealed no gradient profiles were present grains, indicating rate‐limiting step for not diffusion. Thus, D/(D + H) fit first‐order reaction rate law. Apparent kinetic parameters—the constants, activation energies, frequency factors—were Arrhenius equation. Using these expressions, estimated time temperature behavior. apparently relatively fast this implies alteration temperatures should have been very low, likely close 0 °C maintain disequilibrium liquid millions years.