John W. (Jack) Larimer, a pioneer in meteorite research, passed away at the age of 86 on January 22, 2026. Jack attended Lehigh University in Bethlehem, Pennsylvania where he received his bachelors (1962), masters (1963), and doctoral degrees (1966). He spent 1966 – 1969 as a postdoctoral fellow working with Ed Anders at the University of Chicago. Jack joined the geology faculty of Arizona State University in 1969 where he spent the remainder of his academic career.
Jack’s work on nebular condensation chemistry laid the groundwork for many subsequent thermodynamic studies in cosmochemistry, meteoritics, and planetary science, and his papers continue to be cited frequently. His awards and honors include the Nininger Meteorite Award (1966), Meteoritical Society Fellow (1969), a NATO Senior Post-doctoral Fellowship at the MPI für Chemie in Mainz, Germany (1975 – 1976), and an invited visiting professorship at Caltech (1979 – 1980).
In a series of papers (1967-1973), partly together with Ed Anders, he developed the “big picture” of the origin of chondrites as we still understand it today. The importance of Jack Larimer’s work cannot be overestimated. He calculated condensation temperatures of trace elements providing the framework for interpretation of analytical data determined by Anders and his collaborators. Suddenly rare elements such as In and Cd became important to meteoriticists and it was realized that they may tell us something about solar nebular processes. It is the use of chemical evidence from both major and trace elements in the study of meteorites that is so important in this early work of Larimer and Anders.
Jack Larimer pursued this approach further in a number of remarkable papers. In a series of papers, Jack showed oxygen fugacities required for CaS (oldhamite) formation in enstatite chondrites are lower than those in a solar composition gas and hypothesized a slight increase of the C/O elemental ratio accounted for the more reducing conditions in some regions of the solar nebula. His thermodynamic calculations of condensation chemistry as a function of C/O ratio showed condensation temperatures of oxide and silicate minerals decreased with increasing C/O until a new suite of reducing minerals (e.g., oldhamite, MgS niningerite, TiN osbornite) appeared instead. Later working with Ganapathy, Jack analyzed trace elements in CaS and found large enrichments of the rare earth elements (REE) and other lithophile refractory elements, which form refractory sulfides under reducing conditions. Subsequent ion microprobe studies of REE in meteoritic oldhamites found REE abundance patterns that were later explained by condensation calculations at high C/O ratios.
Jack with his postdoc W.R. Kelly authored a classic paper on iron meteorites. Their 1977 GCA paper is the first paper clearly distinguishing between trace element patterns established by condensation and those produced by magmatic processes on the parent bodies. With his paper “Composition of the Earth: Chondritic or Achondritic” Jack Larimer extended his research to the composition of the Earth and its relation to meteorites. He dealt primarily with trace elements and emphasized the similarity of volatile element pattens in the Earth and in some types of meteorites. The general depletion of volatile elements in inner solar system materials is still an important constraint on models of the formation of the solar system.
In summary, Jack Larimer has made fundamental contributions to meteorite research and many of the basic concepts that we use today can be traced back to his creative work.
The two authors of this report have had the privilege of knowing Jack Larimer personally. Jack had a pleasant personality. It was a pleasure discussing with him scientific and non-scientific issues. With his family he spent a year at the Max-Planck-Institute for Chemistry in Mainz. During this time H.P. benefitted greatly from scientific discussions with Jack.
Submitted by Herbert Palme and Bruce Fegley