Gaston: I'd like to cancel a cheque medicine erectile dysfunction treatment pku The researchers also proved that spherules from sites in North America and Europe, thought to be evidence of Younger Dryas comet impacts, didn't come from outer space. Sharma and his colleagues measured osmium isotopes in the melted rock and their surrounding sediment. Meteorites usually carry much more osmium than Earth rocks. (Isotopes are versions of elements with different numbers of neutrons.) But none of the spherules were extraterrestrial, Sharma said.