Toshiko K. Mayeda (née Kuki) (1923–13 February 2004) was a Japanese American chemist who worked at the Enrico Fermi Institute in the University of Chicago.

[6][7] They used mass spectrometry to measure oxygen isotopes in the shells of marine molluscs which gave information on the prehistoric temperatures of ocean waters and hence paleoclimates.

[10][11] When Urey retired from the university in 1958, Mayeda was persuaded to remain there by Robert N. Clayton, and collaborate with him on applications of mass spectroscopy.

[12][21] They published many scientific papers on the "oxygen thermometer" and analysed approximately 300 lunar samples that had been collected during NASAs Apollo Program.

[22] Clayton and Mayeda studied the Achondrite meteorites and showed that variations in the oxygen-17 isotope ratios within a planet are due to inhomogeneities in the Solar Nebula.