In 1946, Brown returned to the University of Chicago to work as an assistant professor of chemistry in the Institute for Nuclear Studies. He was joined by some of his former colleagues from the Manhattan Project and together they became the first team to study
nuclear geochemistry. He went on to study
meteorites and planetary structures along with ways to date the
age of the Earth, encouraging
George Tilton and
Clair Patterson to investigate the
isotopic composition of iron
meteorites. Patterson's studies of
lead eventually led to the first close approximation of the age of the Earth and the
Solar System of 4.5 billion years. Between 1951 and 1977, Brown was professor of geochemistry at the
California Institute of Technology (Caltech). Brown was elected to the
National Academy of Sciences in 1955 and was appointed as their foreign secretary in January 1962, a role that he would hold until 1974. in 1962 a fellow of the
American Geophysical Union, and in 1966 a member of the
American Philosophical Society. He demonstrated an interest in the scientific interactions between the United States and Eastern Europe.
Len Ackland noted that "Geochemistry and his travels in developing countries caused him to ponder the adequacy of the Earth's resources and the problems of development, hunger and population growth." He also wrote a science fiction novel,
The Cassiopeia Affair with Chloe Zerwick. He divorced Adele and married Rudd Owen, who collaborated with him on his writings and social activism. "Man has it within his power today," he said in 1976, "to create a world in which people the world over can lead free and abundant and even creative lives. I am convinced that we can create a world which will pale the Golden Age of Pericles into nothingness." In the early 1970s, he began focusing more on the issues he had developed in his books, including working with a post-doctorate fellow, John P. Holdren, who later became President
Barack Obama's Science Advisor (2009-2017). Brown was appointed first director of the Resource System Institute at the
East–West Center (EWC) in Honolulu. Located adjacent to the
University of Hawaii campus in Manoa, the EWC was a research and educational institution focused on problems in the Asia-Pacific Region. He put together a team of scientists from across the US to follow through even more directly on the ideas he developed in his books, i.e. to explore the sustainability of energy, minerals, and food systems and how they interacted with population and environment. In 1983, in failing health, Brown retired and moved to
Albuquerque, New Mexico with his third wife, Theresa Tellez, his second marriage having also ended in divorce. He became a regular columnist and editor-in-chief of the
Bulletin of the Atomic Scientists. In his last years, Brown battled lung cancer, the treatment for which had resulted in progressive paralysis through the irradiation of his spine. He died in the
University of New Mexico Hospital in Albuquerque on December 8, 1986. He was survived by his third wife Theresa and his son Eric. ==Selected publications==