Obituary Prof. Johannes Geiss (1926-2020)













It is with great sadness that we must bid farewell to our founding father and honorary director

Prof. Johannes Geiss (1926-2020)

Johannes Geiss died on January 30, 2020 at the advanced age of 93. In him, we have lost a great scientist and supporter of the sciences forever.

Johannes Geiss was born on September 4, 1926 in Stolp in what was then Western Pomerania as the son of an estate manager. How different the world must have looked in that time, when his grandfather had the horse hitched to the cart every two days in order to travel to the barber in the neighboring village for a shave; not fifty years later, his grandson landed an experiment on the Moon.

During the war years, Johannes Geiss was able to attend Gymnasium (high school), which he left in 1944 with a Notabitur (early school-leaving qualification in wartime) in order to immediately start a physics degree in Göttingen. Even then, his lecturers must have been struck by the young student’s rapid comprehension and irrepressible need to communication, and he was thus employed as a teaching and research assistant even during his studies. In 1950, he obtained a degree in physics from Max von Laue, and he obtained his doctorate from Wolfgang Paul in 1953. The latter he referred to, with the greatest respect, as the real part of the equally well-known but more flamboyant Wolfgang Pauli, who worked at the ETH at the time; Geiss loved such wordplays which reveal themselves to mathematical initiates.

During his time in Göttingen, Johannes Geiss also met his wife, Carmen, with whom he shared a deep partnership all his life.

His first position as a physicist brought Johannes Geiss to Fritz Houtermans’ institute at the University of Bern. Houtermans wanted to apply mass spectrometry, with which Geiss had successfully been able to determine the isotopic composition of lead, to determine the age of meteoric matter. So, at the beginning of the fifties, his glass mass spectrometer with him, he went to Bern, which would become the new center of his life, and by 1974 he was a naturalized citizen of Switzerland.

Johannes Geiss brought a breath of fresh air to an institute which was perhaps a little outdated at the time and soon found enthusiastic companions to establish a group which would quickly make a name for itself in astrophysics. Periods spent abroad in Chicago with Harold Urey and as a young professor in Miami broadened and rounded out his education; in between, he habilitated in experimental physics, in particular extraterrestrial physics, at the University of Bern in 1957. He was appointed as an associate professor in 1960, and as a full professor in 1964. At the beginning of the sixties, he had to take over management of the institute for the increasingly ill Houtermans, and was thus appointed director of the institute following Houtermans’ death in 1966; a position which he held until his retirement in 1990. In 1970/71, he also served as dean of the Faculty of Science, and in 1982/83 he served as rector of the university.

But Johannes Geiss was pulled to other places time and again in order to maintain and develop his ever-growing network. He spent the year before the first landing mission to the Moon – Apollo 11 – at NASA in Houston in order to lobby for the ingeniously simple solar wind sail developed by him and his group. The solar wind would be captured with an aluminum foil during the astronauts’ time on the surface of the Moon as the solar wind arrives there unhindered because of the Moon’s lack of an atmosphere and a magnetic field. The simplicity of the experiment and the excellent reputation of the Bernese mass spectrometer made him perfect for the job. But it took great tenacity, coupled with the previously mentioned enthusiasm and the necessary bit of luck for the sail, which weighed scarcely a pound, to fly with Apollo 11 in July 1969 and then a further four times. Its analysis, in particular the ratio of the helium isotopes captured, corresponded to a measurement of the average density of the universe as a whole – a ground-breaking result for which he, together with Hubert Reeves, was awarded the Einstein Medal by the Albert Einstein Society in Bern in 2001.

Johannes Geiss made clever use of his growing reputation in order to continue improving the conditions in Bern and to make the institute one of the top names in astrophysics and keep it that way. Under his leadership, the mass spectrometer was made so much smaller that it could be flown on space probes. At the same time, he was able to realize the necessary laboratories and a top-notch clean room in Bern for the tests and calibration. Bern thus became an internationally sought-after partner for space missions, a role which it still retains today thanks to the tireless efforts of Johannes Geiss and his successors. Of the many missions which Johannes Geiss was involved in as principal investigator or as co-investigator, the solar wind ion composition spectrometer stands out as a prime example. Developed with his friend George Gloeckler, this instrument orbited the sun on the Ulysses space probe for almost two decades on a polar orbit. This experiment achieved (among many other results) a refinement of the isotopic signature of helium measured with the solar wind sail. It is hard to find a better illustration of his progressive, unceasing spirit of research.

Even after his retirement, Johannes Geiss’ drive diminished not one jot. He still mustered all of his enthusiasm and convinced those in charge of the European Space Agency ESA and the Swiss Space Center to establish a new institute which would focus on the interdisciplinary analysis, evaluation and interpretation of the results of space missions. The International Space Science Institute was thus born almost exactly 25 years ago. In the first eight years, he served as its executive director and made the institute a center where scientists from all around the world come together in an informal and interdisciplinary setting in order to reach for new scientific horizons. Thanks to his vision, the ISSI has today become a place of meeting and exchange for thousands of space scientists.

Johannes Geiss’ work was internationally recognized with many distinguished honors. He didn’t like the often stiff atmosphere of such events, greatly preferring informal discussions with colleagues, students and anyone at all, when it came to science or any other topic which sparked his enormously broad and active interest. However, some of these honors filled him with a certain amount of pride – and deservedly so: His appointment as a Foreign Associate of the National Academy of Sciences of the USA (1978), his honorary doctorate from the University of Chicago (1986), the aforementioned Einstein Medal (2001) and the Bowie Medal, the highest honor of the American Geophysical Union (2005).

Johannes Geiss passed away in his sleep on January 30, 2020 surrounded by his loved ones. He leaves behind his wife Carmen and his daughter Jana, with her family. His legacy will continue to shine at the Physics Institute at the University of Bern and at the International Space Science Institute.

Bern, February 6, 2020
Rudolf von Steiger


Nachruf Johannes Geiss (Deutsche Version) >>

In Memoriam: Johannes Geiss  – Obituary written by Len A. Fisk and Roger-Maurice Bonnet >>

Pro ISSI Nachruf Johannes Geiss >>