SOME asteroids that formed early in the solar system’s history were covered by oceans of molten rock, or magma.
Richard Greenwood of the Open University in Milton Keynes, UK, and colleagues measured the ratio of two oxygen isotopes in meteorites known to have come from two different asteroids. They found that the ratio of isotopes was identical in every meteorite from the same asteroid, regardless of what part of the asteroid they came from. This suggests that at one time the asteroids must have been molten enough to for these isotopes to be distributed evenly throughout (Nature, vol 435,…
