Science: No News from Planet No. 5

Every so often, a trace of complex organic material discovered in a meteorite leads scientists to a romantic conclusion. Such chemical traces of life, they say, must mean that the meteor came from a place where life once existed. Most plausible spot: Planet No. 5, which some scientists believe revolved several billion years ago between Mars and Jupiter and later disintegrated to form the swarms of asteroids that now occupy the No. 5 orbit.

Geologist Egon T. Degens of Caltech has all but destroyed this romantic notion. Taking samples from the interiors of two porous nonmetallic meteorites —the sort that are supposed...