University of Rochester New research at the Laboratory for Laser Energetics provides clues to the evolution of the solar system. Nearly 40 years ago, scientists predicted the existence of helium rain inside planets composed primarily of hydrogen and helium, such as Jupiter and Saturn. But achieving the experimental conditions necessary to test this hypothesis has not been possible. That is, until now. In a paper published in Nature, scientists at the University of Rochester, together with an international collaboration, reveal experimental evidence showing that helium rain-helium droplets falling through liquid metallic hydrogen, much like raindrops of water falling through the atmosphere on Earth-is possible over a range of pressure and temperature conditions that mirror those expected to occur inside planets such as Jupiter and Saturn. The discovery will help scientists determine how such planets form and will provide key insight into the evolution of Earth and the solar system.