Robert Clayton
The chemist who discovered that oxygen isotopes give every meteorite group its own fingerprint, the key to telling where meteorites come from.
Key facts
- Born
- 1930
- Died
- 2017
- Nationality
- Canadian-born American
- Field
- Geochemist
Robert Norman Clayton was born in Canada and spent most of his career at the University of Chicago, where he worked closely with the chemist Toshiko Mayeda for more than thirty years.
Oxygen has three stable isotopes, oxygen-16, oxygen-17 and oxygen-18. In rocks from Earth, the amounts of the two heavier ones change together in a fixed ratio, so all Earth rocks fall on one line when plotted on a graph. In 1973 Clayton, Mayeda and Lawrence Grossman found that the white inclusions in the Allende meteorite did not fall on that line. They were rich in oxygen-16 in a way no ordinary chemical process could explain.
This discovery opened up a powerful tool. Clayton and Mayeda went on to measure the oxygen isotopes of every kind of meteorite. Each group, from ordinary chondrites to the meteorites from Vesta and Mars, has its own position on the graph, a fingerprint of the place in the Solar System where it formed. Oxygen isotopes are now used to classify new meteorites and to test which ones are related.
The method helped prove that the first lunar meteorite came from the Moon and that the SNC meteorites share a single parent, now known to be Mars. Clayton received many honours, including the Leonard Medal and the National Medal of Science.
On the timeline
- 1973Oxygen isotopes fingerprint meteorites
- 18 January 1982The first meteorite recognised from the Moon
See more
The Allende meteoriteThe Allan Hills 81005 meteorite