Significance In this study we report the discovery of a previously unrecognized chemical class, dihydroxymagnesium carboxylates, [(HO) ₂ MgO ₂ CR] ⁻ , gained from nonterrestrial meteoritic analyses. The existence of such low-coordination organomagnesium anionic compounds expands our knowledge and understanding of extreme environments from which the early solar system emerged and has evolved. The appearance this CHOMg chemical class extends the previously investigated vast diversity of CHNOS groups in meteoritic soluble organics. Experimental evidence is given for the connection between the evolution of organic compounds and minerals. These thermostable compounds might have contributed to the stabilization of organic molecules on a geological time scale, which emphasizes their potential astrobiological relevance.