Peter Signer, an eminent pioneer of noble gas geochemistry, died on December 10, 2021, following a lengthy illness. He was 92 years old.

Signer graduated from the Physical Institute of the University of Bern under the directorship of Friedrich Houtermans. One of Signer’s pioneering studies was his first mass spectrometric investigation of the decay constant of lutetium-176. In 1958, he went to the University of Minnesota to work with Alfred Nier, who was known as the father of modern mass spectrometry.

Over the next seven years, Signer developed his affection for both noble gases and meteorites. One of his widely known contributions was the development, together with Nier, of the “Signer-Nier model” for the production of cosmogenic nuclides in iron meteorites. Some of his other contributions included working with Hans Suess in 1963 to compile a complete dataset of meteorites containing primordial noble gases. Signer pointed out that solar gases in meteorites might be trapped particles of solar corpuscular radiation, a conclusion that was drawn independently at the same time by Heinrich Wänke.

Solar gases in meteorites and lunar material occupied a considerable part of Signer’s research activities for the next 30 years. In 1965, Signer returned to Switzerland to join Marc Grunenfelder in the newly established Laboratory for Isotope Geochemistry at the ETH Zurich. While there, Signer created a noble gas laboratory devoted mainly to studies of extraterrestrial materials. The backbone of that lab was two Nier-type mass spectrometers imported from Minneapolis. Those machines went on to devour thousands of lunar, meteorite, and terrestrial samples.

Signer, a Fellow of the Meteoritical Society since 1967, was an enthusiastic lecturer who reminded generations of Earth science students about the importance of understanding the other planets to understand Earth. He was a good friend and teacher, and we mourn his loss.

— Portions of text courtesy of Rainer Wieler, Ludolf Schultz, and the Meteoritical Society