In most careers, being wrong too often is grounds for dismissal. False prophets in ancient kingdoms were stoned or shamed out of town. Only in science, it seems, can experts consistently get it wrong, and not only keep their jobs, but be highly esteemed as experts. Among the guiltiest of the lot are planetary scientists, whose predictions have been consistently wrong for almost every planetary body studied since the dawn of the space age. Their orbital mechanics is solid; they do get their spacecraft to arrive at the right place at the right time with uncanny accuracy. But what the missions reveal is often completely different from what scientists had told the public they expected to find. This has been true of Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, comets, asteroids, and most of the moons of the solar system, where hasty revisions have had to be made after spacecraft data falsified the predictions. Here are some recent examples of “theory fail” in planetary science.