Viti crater at dusk, Krafla volcanic area, Myvatn, Nordhurland Eystra, Iceland
Two abiotic cycles each oxidize glyoxylate into CO 2 with the regeneration of oxaloacetate. All reactions of both the HKG and Malonate cycles progress signi ficantly in hours at pH values 7 –8.5 at the listed temperature of 50 °C or 23 °C