In the 1983 Alvarez experiment, researchers used an iridium anomaly to test the asteroid-impact explanation for dinosaur extinction.
Luis Alvarez, Walter Alvarez, Frank Asaro, and Helen Michel examined the thin boundary layer separating Cretaceous and Paleogene rocks. They found unusually high concentrations of iridium, an element relatively scarce in Earth’s crust but more abundant in many meteorites.
The finding supported the proposal that a large extraterrestrial impact occurred around the time of the mass extinction about 66 million years ago. Later research identified the Chicxulub impact crater in the Yucatán Peninsula and supplied additional geological evidence.
The evidence did not come from a laboratory experiment in the narrow sense; it was a geological investigation and hypothesis test. The iridium layer alone did not identify the crater or prove every detail of the event, but it was a crucial clue linking the extinction boundary to extraterrestrial material.