Timo Hopp studied Geosciences at the University of Münster, where he completed his doctoral thesis at the Institute of Planetology in 2018. He subsequently worked as a Postdoctoral Scholar in the Department of the Geophysical Sciences at the University of Chicago (USA) and, since June 2022, has been a scientist and laboratory head in the Department of Planetary Sciences at the Max Planck Institute for Solar System Research in Göttingen.

Timo Hopp is a cosmochemist who investigates the early history of the Solar System and the formation of the planets using high-precision isotope measurements. His research is distinguished by the application of state-of-the-art analytical methods, many of which he either developed from scratch or significantly improved to achieve unprecedented analytical precision. His work has provided fundamental new insights into the formation of the first planetary bodies in the Solar System and the origin of the Earth.

During his doctoral research, Timo developed mass-dependent ruthenium (Ru) isotope fractionation as a new tool for investigating the differentiation history of protoplanets and the origin of the Earth's so-called Late Veneer. He demonstrated that the mass-dependent isotope fractionation of Ru varies systematically with the degree of chemical differentiation of planetary bodies, allowing the different stages of metal melt formation, segregation, and crystallization during core formation to be reconstructed using Ru isotopes. In a subsequent study, he showed that, unlike the variable isotope fractionation observed in differentiated meteorites, ruthenium in the Earth's silicate mantle is isotopically unfractionated and exhibits the same isotopic composition as undifferentiated chondritic meteorites. Because virtually all ruthenium in the silicate Earth originates from the Late Veneer—the final approximately 0.5% of Earth's mass accreted after core formation—this finding demonstrates that the Late Veneer most likely consisted of chondritic material rather than chemically differentiated bodies, as had previously been suggested.

Another major focus of Timo Hopp's research concerns nucleosynthetic isotope anomalies, which arise from the heterogeneous distribution of isotopically anomalous presolar components within the protoplanetary disk. These anomalies provide powerful tracers for identifying genetic relationships among planetary materials and reconstructing the origin of the Earth's building blocks. Using ruthenium and molybdenum isotope anomalies, he demonstrated that the final stages of Earth's accretion involved a heterogeneous mixture of material from both the inner and outer Solar System. In contrast, studies of iron isotope anomalies showed that the Earth was formed predominantly from material originating in the inner Solar System, with only a minor contribution from the outer Solar System. This finding contradicts predictions from recent planet formation models in which the terrestrial planets acquire much of their mass through the accretion of centimeter-sized "pebbles" from the outer Solar System.

Instead, Timo's results support the classical model of planet formation, in which the terrestrial planets formed through collisions between Moon- to Mars-sized planetary embryos originating in the inner Solar System. In another groundbreaking study of samples returned from asteroid Ryugu by the Japanese space agency JAXA's Hayabusa2 mission, which delivered 5.4 grams of material to Earth, Timo demonstrated that Ryugu's iron isotope composition matches that of CI (Ivuna-type) carbonaceous chondrites and differs from all other carbonaceous chondrites. This discovery has far-reaching implications, indicating that CI chondrites originated in a different region of the protoplanetary disk than other carbonaceous chondrites. Since the latter are thought to have formed just beyond Jupiter's orbit, this suggests that CI chondrites and Ryugu may have originated even farther from the Sun, perhaps in the region of Uranus and Neptune. If confirmed, CI chondrites, Ryugu, and comets may ultimately derive from the same source material—a hypothesis that could be tested by a future sample-return mission to a comet.

Although most of Timo Hopp's research has focused on cosmochemistry, his scientific interests extend far beyond this field. In 2020, he used isotope measurements of residues collected from air filters by the International Atomic Energy Agency to determine the origin of radioactive ruthenium released in 2017. While the leading hypothesis suggested an accident at a Russian nuclear fuel reprocessing facility, it had also been proposed that the material might have originated from the production of weapons-grade plutonium. By measuring isotopes in only a few nanograms of ruthenium collected from air filters before, during, and after the release, Timo identified a Russian reprocessing plant as the source. This work represented a major scientific achievement with significant public and political relevance and marked the first application of ruthenium isotopes as a tool in nuclear forensics.

By awarding the Victor Moritz Goldschmidt Prize to Timo Hopp, the German Mineralogical Society honors an exceptionally innovative, creative, and productive scientist whose work is characterized by remarkable scientific breadth and has led to fundamental advances across several fields of research.

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Thorsten Kleine ∙ Göttingen