May 18, 2018

Friedrich Begemann passed away on May 11, at the age of 90. Friedrich (‘Fred’) was the director of the Isotope Cosmology Department at the Max-Planck-Institut für Chemie (MPI-C) in Mainz (Germany) from 1978 until his retirement in 1995 and the 1995 recipient of the Meteoritical Society’s Leonard Medal.

Friedrich Begemann was born in late 1927 in the small village of Almena in Westphalia, close to the border to Lower Saxony and near the river Weser. Too young to get drafted for serious military service in World War II, he took up a study of physics at the University of Göttingen in 1947 and completed his diploma thesis working with Friedrich Houtermans, who by then had returned to Göttingen after being forced to leave in 1933. When Houtermans moved to Bern, Switzerland, in 1952, Begemann followed him there (together with Johannes Geiss) to work on his PhD thesis. In his work with Houtermans Friedrich Begemann dealt with the products of the radioactive decay of U and Th into (eventually) isotopes of lead. He determined the half-life of radioactive Ra-E (210Bi), an isotope in the decay chain leading from 238U to 206Pb, and applied the Ra-D (210Pb) method suggested by Houtermans to determine a ‘chemical age for minerals’. Counting activities was a major part of this work, but even in these early days already mass spectrometric determinations of lead isotopes.

Following his Ph.D. work, Friedrich Begemann moved to Chicago to work with Willard F. Libby as a Research Associate at the Enrico Fermi Institute. Here he focused on tritium (3H), the radioactive isotope of hydrogen, and over the following decade published a number of important papers on its abundance, origin and distribution. This was a hot topic at the time due the enormous amounts of tritium released into the environment from hydrogen bomb tests. Drawn to the group of Harold Urey and the likes of (again) Johannes Geiss and Jerry Wasserburg also at Chicago, it was at this time that Friedrich Begemann got into contact with meteorites and analyses of stable noble gas isotopes, specifically 3He, the decay product of tritium. His paper with Johannes Geiss and D.C. Hess, in which they reported the first determination of a cosmic-ray exposure (CRE) age of a meteorite from combined tritium/3He analysis is a milestone. It set the stage for the development of a completely new branch in Meteoritics. The study of cosmic ray products in meteorites today is a mature field. Not only does it provide the means to determine exposure ages, thus travel times from parent body to Earth, but it also puts constraints on their pre-atmospheric size – both very basic properties.

Back to Germany in 1957, Friedrich Begemann joined Friedrich Paneth at the MPI-C in Mainz, where he remained until his retirement in 1995, interrupted only by a short stint as a Guest Professor at the University of Bern. Within a short time in Mainz he also became an adjunct professor at Johannes-Gutenberg University, teaching Experimental Physics in addition to doing research at the Max-Planck-Institute. While his early work in Mainz is still dominated by the study of radiation effects, including such in rocks brought back from the Moon by Apollo, with time he focused more on the mass spectrometric determination of stable isotope compositions, noble gases in particular, but also elements like potassium and magnesium, where he was one of the first to confirm the existence in the early Solar System of now extinct 26Al from overabundances of 26Mg in CAIs found by his good friend Jerry Wasserburg.

Having already been appointed a ‘Scientific Member’ of the Max-Planck Society in 1969, Friedrich Begemann became the director of a new Department at the MPI-C in 1978, which he led until his retirement in 1995. This allowed him to expand this direction of research. A number of important contributions from this time, to mention a few, deal with noble gases in Martian meteorites and the isotopes of noble gas and other trace elements in presolar grains. He also contributed to refined understanding of cosmic ray interactions with meteorites by pointing out the “matrix effect” and by enabling the performance of irradiation simulation experiments on artificial meteorites. For this and his earlier work he was awarded the Leonard Medal of the Meteoritical Society in 1995. He also served the Society as a councilor from 1981 to 1984 and together with Heinrich Wänke organized the 1983 Annual Meeting with an unforgettable evening tour and Dinner on the Rhine River.

Friedrich Begemann contributed strongly to making and keeping contact with friends and colleagues in the former East Bloc, in particular Russia, from where numerous guests came to visit and perform research at the Max-Planck Institute, in particular in the early 1990s after the opening of the Wall. China was also on his mind, and when the country began to open up after the end of the Cultural Revolution, he was a member of the first delegation from the Max-Planck Society visiting China to establish scientific contact. He also led the consortium study of the large Jilin meteorite, the results of which were published in EPSL in 1985 and in MAPS in 1996.

Many of us will not know that cosmochemistry was not the only scientific endeavor of Friedrich Begemann during his productive years and also after his official retirement. Rather than only the origin and history of the Universe and the Solar System, he also made important contributions in archaeometry – getting insight into the history of humankind. For this, he revisited what he had done during his diploma and doctoral theses – the decay of U and Th into lead, but now solely by precise mass spectrometric studies of lead isotopes. His work in this field, involving studies of ores and early metal artefacts from places like Troia and Lesbos, among others, contributes to our knowledge of the sources of raw metals such as tin and copper as they were used during the Bronze Age, which in turn tells us about trade patterns during this time.

A defining characteristic of Friedrich Begemann was his analytical mind and sharp wit, where he was second to none. He was able to detect the slightest flaw or uncertainty in your logic and he would tell you so. Sometimes this may have been hard to take by some of us, but we definitely need such minds!

Friedrich Begemann’s wife Margarete died slightly more than a year ago, and after that also Friedrich’s health started to deteriorate. His sharp mind, however, remained to the last day. He leaves daughter Marieluise, son Hanns-Friedrich and granddaughter Eva.

—Ulrich Ott

Categories: In Memoriam