Thiemens earned his bachelor of Science degree from the University of Miami. His studies with isotope geochemist Cesare Emiliani, PhD student of Harold Urey and a co-discoverer of paleoclimate temperature determination stimulated his interests in isotopes. Thiemens received a MS from Old Dominion University and PhD from Florida State University for his research using stable isotopes and particle identification using the FSU Van de Graff accelerator. He moved to the University of Chicago at the Enrico Fermi Institute for Nuclear Studies (1977-1980) where he worked with Robert N. Clayton using lunar samples to track solar wind origin and evolution, meteorite cosmochemistry, and early atmospheric chemistry.