Illustration showing shallow lightning on the dark side of Jupiter. This phenomenon was detected by the Stellar Reference Unit camera of NASA's Juno spacecraft. Scientists suggest that shallow lightning occurs on Jupiter because thunderstorms cause water ice crystals to be flung up into the atmosphere where they react with ammonia vapour. This forms a solution consisting of ammonia and water. The ammonia prevents the water ice from freezing in the extreme cold temperatures of Jupiter's atmosphere by reducing the melting temperature, acting as antifreeze. Falling ammonia-water droplets then collide with rising water ice crystals, separating charge. This produces cloud electrification, which causes the shallow lightning in Jupiter's upper atmosphere.