Dr. John Hume Jones (known to all as “JJ”) died on April 13, 2025, in Houston, Texas, succumbing to complications from a chronic illness. He was a towering figure in experimental petrology who helped lay the foundations of quantitative and theoretical trace element partitioning.1 JJ also contributed significantly to planetary materials and sample science, focusing on basalts -- especially eucrites and martian meteorites. A candid (and puckish) story of his life and times, with an overview of his career and research, appears in his Geochemical Perspectives retrospective1 which we highly recommend.
John Hume Jones was born on July 24, 1952 in Ekron, Kentucky, and raised there -- the only child to parents of modest means. After high school, he enrolled at the University of Kentucky in nearby Louisville, majoring first in Chemistry, and then Geology. John graduated in 1974, but his degree was only in General Studies since he refused to take the required course in paleontology! JJ loved Kentucky Wildcat basketball and carried that passion the rest of his life.
JJ must have done well at Kentucky: the meteorite radiochemist William Ehmann there recommended him to the Ph.D. program at Caltech, and JJ was accepted. According to Chuck Douthitt2, JJ’s move from KY to CA “simultaneously lowered the average IQs of both states.” Working with Don Burnett (PI of the Genesis Mission) at Caltech3, JJ studied the partitioning of actinide elements between silicate minerals and melts, and implications for their abundances in the early solar system. He received a Ph.D. in 1981.4
John’s dry sense of humor was evident in his search for permanent employment after his doctorate: “… Bill McKinnon (Washington U., St. Louis) and I placed a job-wanted ad in EOS. The ad was mostly written by Bill, who is rather better-trained in the classics than I am. We advertised ourselves as Philosopher Kings who were applying for ‘hereditary positions of power and influence.’ But mysteriously, no job offers arose from this advertisement. Apparently, Philosopher Kings were not in great demand at the time.” 1
Bending to cruel reality, JJ applied for and was accepted into a post-doc position with Michael Drake (University of Arizona), despite Burnett’s tepid recommendation.5 At Arizona, JJ followed in the line of many of Drake’s other students and post-docs, including Guy Consolmagno, Horton Newsom, Duck Mittlefehldt, Charles Hostetler, Jack Berkley, Allan Treiman, and Nancy Chabot. JJ’s work under Drake included constraining the composition of core of the eucrite parent body (now Vesta), determining partition coefficients of siderophile elements between solid and liquid metals, and of transition elements between olivine and basaltic melts.
After Arizona, in 1986, JJ continued experimental work at Johnson Space Center in the group now known as ARES (Astromaterials Research and Exploration Science). JJ was the consummate experimentalist, carefully designing experiments to give scientifically useful results regardless of their outcomes.6 Following in Drake’s footsteps, most of JJ’s experimental work was on the distribution of trace elements between minerals and basaltic melts1. His focus was using olivine and on siderophile elements as clues to planet assembly and core formation. He used his experimental partition coefficients in thermochemical models1, helping to establish the predictive formulations now in use. Quantifying partition coefficients requires precise analyses, so JJ collaborated with Gordon McKay (JSC), who became his close friend and analytical guru.7 JJ leveraged those experimental results into ground-breaking studies of the origins of asteroidal achondrites, martian meteorites, and Mars’ volatiles.
Duck Mittlefehldt had also joined the team at JSC and, over a beer or two (probably at Boondoggles), they bet on whether partial melts of chondrites would be like eucrite or angrite basalts. To resolve the bet, Amy Jurewicz (later of Genesis fame with Burnett) partially melted chondrite compositions in JSC’s experimental lab. Her results showed that Duck and JJ owed each other beers.8 In addition to Amy, JJ mentored and advised many interns, post-docs, and visiting scientists, including: Steve Jurewicz (retired), Tomohiro Usui (ISAS / JAXA), Ben Hanson (Corning), Nancy Chabot (APL), Jack Berkley (retired), Valerie Malavergne (Gustav Eifel Univ.), Alex Borisov (Russian Acad. Sci.), Chris D.K. Herd (U. Alberta), and many others.
Several of JJ’s most significant contributions were on the martian meteorites, then known as ‘SNCs’. Their martian origin was first publicly asserted by Ashwal9, and confirmed in 1983 when Don Bogard (JJ’s colleague at JSC) showed that composition of noble gases in a an SNC matched the in situ analysis of the martian atmosphere by the Viking spacecraft. However, the SNCs’ origin remained contentious, as the radioisotope community interpreted their ancient U-Pb radiometric ages, ~4500 my, to record (like other achondrites) crystallization from magmas, and that younger ages represented impact events. In 1986, JJ overturned this view by showing that the 180 my Sm-Nd age of the Zagami SNC was its crystallization10, and thereby aligned radioisotope chronology with the geomorphology and crater-count chronology of Mars’ surface. The idea of ancient shergottite crystallization resurfaced two decades later, and JJ again refuted it.11
Recognizing the limitations of the martian meteorites, JJ was a strong advocate for Mars sample return. His legacy here is the elevator-speech phrase, that a returned sample is a ‘gift that keeps on giving.’12
Outside of work, JJ enjoyed pursuing his family’s genealogy - not a simple task given the name Jones! He traced family roots to Ireland13 and visited a family ancestral home. JJ was unable to discover the source of his middle name, and it remains a mystery.
As his health deteriorated, JJ slowed but he continued to work in element partitioning.14 A manuscript with Justin Simon (JSC) on the radiogenic isotope systematics of the martian meteorites was started but not completed. JJ finally succumbed in hospital; several of his closest friends were with him at the end. Those of us who knew and loved JJ will appreciate that he left us, not with a bang or a whimper, but with an expletive.15
1. Jones J.H. (2016) Thoughts and reminiscences on experimental trace element partitioning. Geochemical Perspectives 5(2), 147 pages.
2. Chuck Douthitt was contemporary with JJ at Caltech, studying Si isotope geochemistry. Later, Chuck was known across sample science as the consummate salesman of mass spectrometers. Less well known is that one year in Ann Arbor, MI, Chuck overwintered in a tent on the golf course.
3. For a while at Caltech, JJ shared an apartment with Steve Smith. This led to inevitable questions of what their names really were, why they were hiding, and why they had taken such obvious aliases.
4. Jones, John Hume (1981) Studies of the Geochemical Similarity of Plutonium and Samarium and Their Implications for the Abundance of ²⁴⁴Pu in the Early Solar System. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/qwv9-t340. https://resolver.caltech.edu/CaltechETD:etd-10052006-093021
5. A synopsis, told to Jones by Drake. “(i) Jones is not a very good student; (ii) he’s not a very good researcher; (iii) he will probably never make any important scientific contributions; but (iv) he’s probably better than anyone on [the Arizona planetary] faculty.”1
6. Exceptions to his meticulous procedures were the infamous Bathpunch experiments, for which Dave Walker bears significant responsibility. Jones J.H., Walker D., Pickett D.A., Murrell M.T., & Beattie P. (1995) Experimental investigations of the partitioning of Nb, Mo, Ba, Ce, Pb, Ra, Th, Pa, and U between immiscible carbonate and silicate liquids. Geochimica et Cosmochimica Acta 59, 1307-1320.
7. Gordon’s untimely death, and that of his wife Linda Uljon, were devastating to JJ and the science community.
8. Partial melting of chondrites can produce both angrite- and eucrite-like melts, depending on oxygen fugacity. JJ bet for eucrites; Duck bet for angrites; Amy didn’t bet and so got no beer. Jurewicz A.J.G., Mittlefehldt, D.W., & Jones J.H. (1991) Partial melting of the Allende (CV3) meteorite: implications for origins of basaltic meteorites. Science, 252, 695-698. Jurewicz A.J.G., Mittlefehldt D.W., and Jones J.H. (1993) Experimental partial melting of the Allende (CV) and Murchison (CM) chondrites and the origin of asteroidal basalts. Geochimica et Cosmochimica Acta 57, 2123-2139. Jurewicz A.J.G., Mittlefehldt D.W., & Jones J.H. (1995) Experimental partial melting of the St. Severin (LL) and Lost City (H) chondrites. Geochimica et Cosmochimica Acta, 59, 391-408. Usui T., Jones J.H., and Mittlefehldt D.W. (2015) A partial melting study of an ordinary (H) chondrite composition with application to the unique achondrite Graves Nunataks 06128 and 06129. Meteoritics & Planetary Science, 50(4), 759-781.
9. Ashwal L.D., Warner J.L., and Wood C.A. (1982). SNC meteorites: evidence against an asteroidal origin. Proc. 13th LPSC, Journal of Geophysical Research: Solid Earth, 87(S01), A393-A400.
10. Jones J.H. (1986) A discussion of isotopic systematics and mineral zoning in the shergottites: Evidence for a 180 my igneous crystallization age. Geochimica et Cosmochimica Acta 50, 969-977.
11. Jones J.H. (2015) Various aspects of the petrogenesis of the Martian shergottite meteorites. Meteoritics & Planetary Science, 50(4), 674-690.
12. ‘Borrowed’ without attribution from Hallmark© advertisements of the time. Jones J.H. and Treiman A.H. (1998) Bringing Mars home: Opportunities and challenges presented by the Mars sample return mission. Lunar and Planetary Information Bulletin 85, 12 (https://www.lpi.usra.edu/captem/mars.html ).
13. JJ was also a fan of music, with eclectic tastes including both The Travelling Wilburys and Tom Lehrer. With JJ’s ancestry in mind, the narrators would quote Lehrer’s The Irish Balad on the length of this memorial: “My tragic tale I won’t prolong, and if you do not enjoy my song, You’ve yourself to blame if it’s too long, you should never have let me begin.”
14. Usui, T., Righter, K., Shearer, C. K., & Jones, J. H. (2022) Effect of sulfur on siderophile element partitioning between olivine and a primary melt from the martian mantle. American Mineralogist, 107(3), 357-368.
15 JJ: “Am I dying?” Loan Le: “Yes, John.” JJ: “Shit.”
Submitted by Allan Treiman, Amy Jurewicz, Duck Mittlefehldt, Justin Simon.