Thomas McCord
The planetary scientist who showed in 1970 that the asteroid Vesta has the same colours as basaltic meteorites, and later worked on the Dawn mission.
Key facts
- Nationality
- American
- Field
- Planetary scientist
Thomas B. McCord pioneered the study of planets and asteroids by measuring the colours of the sunlight they reflect, a method called reflectance spectroscopy. Different minerals absorb light at particular wavelengths, especially in the near infrared, so the spectrum of an asteroid gives clues to what its surface is made of.
In 1970, working at the Massachusetts Institute of Technology, McCord and his colleagues Jack Adams and Torrence Johnson measured the spectrum of Vesta with a telescope. They found a strong absorption caused by the mineral pyroxene, and the spectrum closely matched laboratory measurements of eucrites, the basaltic achondrites. It was the first time a type of meteorite had been linked with a particular asteroid.
This was a remarkable result. It suggested that Vesta had once melted and erupted lava onto its surface, and that the howardites, eucrites and diogenites found on Earth were pieces of it. Later work found small asteroids with the same spectra spread out from Vesta towards a resonance with Jupiter, showing how fragments reach Earth.
More than forty years later, McCord was a member of the science team for NASA's Dawn mission, which orbited Vesta in 2011 and 2012 and confirmed the link close up.
On the timeline
- 1970Vesta's colour matches a meteorite
- 16 July 2011Dawn arrives at Vesta