I can’t blame a planetary scientist for thinking, as Brett Denevi espouses in “The new Moon” (Physics Today, June 2017, page 38), that modern planetary science began when we went to the Moon. Actually, it was alive and well for quite a few years before that. A better birth date might be 1942, when Austrian refugee Friedrich Paneth, working with two colleagues, discovered an excess of helium-4 in several iron meteorites, which indicated that the universe was older than was currently accepted.1
World War II shut down such research, but by 1948 the excess helium was postulated to have originated from nuclear reactions induced by cosmic radiation.2 Fred Singer calculated, and Paneth verified,3 the relative cosmogenic production rate of 3He. Their work encouraged the use of meteorites as space probes well before rockets were available.
Further research followed. Fritz Houtermans established the Institute of Physics at the University of Bern, and Claire Patterson at Caltech used lead isotopes to narrow the age of Earth to four and a half billion years.4 In 1960 John Reynolds found evidence of the extinct radionuclide iodine-129 in the isotopic composition of xenon in the Richardton meteorite,5 and further isotopic analyses of meteorites brought forth a plethora of data, which soon extended to many other elements. (The xenon spectrum alone provided jobs and funding to a whole generation of graduate students.)
In the mid 1960s, a group of planetary scientists led by John Wasson at UCLA took over an amateur group called the Meteoritical Society and transformed it into a vibrant source of international meetings and cooperation, augmented by yearly Gordon Research Conferences and various European meetings sponsored by the International Atomic Energy Agency. Before the first Moon landing in 1969, cosmochemistry laboratories were active in Japan, the USSR, Australia, France, the UK, Switzerland, and Germany. In the US, there were such labs at several universities—UC Berkeley, UC San Diego, Chicago, Minnesota, Arkansas, Missouri, Carnegie Mellon, and Cornell—and at Brookhaven National Laboratory and the Harvard–Smithsonian Center for Astrophysics.
When we finally went to the Moon, we were indeed enthusiastically expectant, largely because of Nobel laureate Harold Urey’s suggestion that lunar data would be the Rosetta stone of the solar system, unlocking the mysteries of its birth and development.
Well, Urey’s suggestion may come true someday. But right now it seems that human exploration of the Moon is perhaps a large blip in the history of planetary science rather than its originating moment.
Further details can be found in my book Much Ado About (Practically) Nothing: A History of the Noble Gases (2010). I apologize to the many planetary scientists whose early work is not mentioned here due to lack of space and my own limitations.
