How did water get into the upper atmosphere of Jupiter? That has been a mystery since 1997, but one that has now been solved with the help of the Herschel Space Observatory.The water in the stratosphere didn’t make sense because it couldn’t have come from a local source. The reason for that being the so-called “cold trap” between the upper atmosphere and the cloud below it on the planet. Other ideas as to what caused it all focused on an external source, such as an ice ring, interplanetary dust particles, or even a comet.Now the mystery has been solved, with the source of the water being the Shoemaker-Levy 9 comet. It broke apart and impacted with Jupiter on July 9, 1994 over the course of a week and scarred the surface with 21 fragments. We didn’t discover the water in the upper atmosphere of the planet until 1997 when the ESA’s Infrared Space Observatory (ISO) had a look.Astronomers have always believed that Shoemaker-Levy 9 was probably the source of the water, but without proof they couldn’t state it as fact. However, in May 2009 the Herschel Space Observatory was launched with a Heterodyne Instrument for the Far Infrared (HIFI) instrument on board.Looking at Jupiter with HIFI, it was found that the planet had up to 3 times more water in its southern hemisphere than the northern hemisphere. The most water was found above the sites where the comet fragments landed. The lack of uniform distribution means that everything except a comet or moon can be ruled out as the delivery system. And as none of Jupiter’s moons are in the right location to perform such a transfer, the water must have come from the comet.