Toshiko Mayeda
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Born	Toshiko K. Kuki 1923 (1923) Tacoma, Washington
Died	13 February 2004(2004-02-13) (aged 78–79)
Alma mater	University of Chicago
Known for	Study ofmeteorites and ofisotopes of oxygen
Scientific career
Institutions	University of Chicago
Academic advisors	Robert N. Clayton

Toshiko K. Mayeda (née Kuki) (1923–13 February 2004) was a Japanese American chemist who worked at theEnrico Fermi Institute in theUniversity of Chicago. She worked on climate science and meteorites from 1958 to 2004.

Toshiko Mayeda was born inTacoma, Washington.^[1] She grew up inYokkaichi, Mie, andOsaka.^[1] When the United States enteredWorld War II after the Japaneseattack on Pearl Harbor, she and her father Matsusaburo Kuki were sent to theTule Lake War Relocation Center.^[2][3] Whilst there she met her future husband, Harry Mayeda.^[4] After the war, she graduated with a bachelor's degree in chemistry from theUniversity of Chicago in 1949.^[5]

Mayeda worked initially as a laboratory assistant toHarold Urey at the University of Chicago, where she was hired initially to wash glassware.^[6][7] They usedmass spectrometry to measureoxygen isotopes in the shells of marinemolluscs which gave information on the prehistoric temperatures of ocean waters and hencepaleoclimates.^[8] Urey developed the field ofcosmochemistry and with Mayeda studied primitivemeteorites, also by usingoxygen isotope analysis.^[9] Later, she worked withCesare Emiliani on isotopic evaluation of theice age.^[10][11] When Urey retired from the university in 1958, Mayeda was persuaded to remain there byRobert N. Clayton, and collaborate with him on applications of mass spectroscopy.^[12] She was described as anindomitable research assistant.^[13][14]

Mayeda and Clayton's first research paper considered the use ofBromine pentafluoride to extractIsotopes of oxygen from rocks and minerals.^[15] It remains their most cited work.^[8] From the 1970s until the late 1990s Mayeda and Clayton became famous for their use of oxygen isotopes to classify meteorites.^[12] They developed several tests that were used across the field of meteorite and lunar sample analysis.^[16][17][18] They studied variations in the abundances of the stable isotopes of oxygen,oxygen-16,oxygen-17 andoxygen-18,^[19] and deduced differences in the formation temperatures of the meteorites.^[20] They also worked on the mass spectroscopy and chemistry of theAllende meteorite.^[12][21] They published many scientific papers on the "oxygen thermometer" and analysed approximately 300 lunar samples that had been collected duringNASAsApollo Program.^[8][14]In 1992, a new type of meteorite, theBrachinite, was identified.^[22] Clayton and Mayeda studied theAchondrite meteorites and showed that variations in the oxygen-17 isotope ratios within a planet are due to inhomogeneities in theSolar Nebula.^[23] They analysedShergotty meteorites, proposing that there could have been a water-rich atmosphere onMars^[24] and studied the Bocaiuva meteorite, finding that theEagle Station meteorite was formed due to impact heating.^[25]

In 2002 Mayeda was awarded the Society Merit Prize from theGeochemical Society of Japan.^[7] In the same year, an asteroid was named after her.^[7] Mayeda's husband, Harry, died in 2003. Mayeda suffered from cancer and died on February 13, 2004.^[7] In 2008, the bookOxygen in the Solar System was dedicated to Clayton and Mayeda.^[26]

• Glenn J. MacPherson, ed. (2008).Oxygen in the Solar System.ISBN 9780939950805.

• American people of Japanese descent
• American women chemists
• University of Chicago alumni
• University of Chicago faculty
• American geochemists
• 1923 births
• 2004 deaths
• People from Tacoma, Washington
• People from Yokkaichi
• Scientists from Osaka
• Japanese-American internees
• 20th-century American women
• American women academics
• 21st-century American women

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