It appears that the mystery of how water got into the atmosphere of Jupiter has finally been solved.

The European Space Agency (ESA) today announced that the water in the Jovian planet’s upper atmosphere has been linked to the 1994 Shoemaker-Levy 9 impacts. The comet Shoemaker-Levy 9 broke up and collided with Jupiter in July of 1994. The week-long event, which was the first directly-seen extraterrestrial collision in the Solar System, was observed by astronomers around the world.

Though astronomers suspected the Shoemaker-Levy impacts were the source of the water, the ESA’s Herschel space observatory has now been able to map the vertical and horizontal distribution of the water in Jupiter’s atmosphere. The observatory’s infrared imaging was able to discern that there is two to three times more water in Jupiter’s southern hemisphere than in the northern hemisphere. Shoemaker-Levy hit Jupiter’s southern hemisphere, and Herschel has found “most” of the water is concentrated around the impact sites. The findings have been published in the journal Astronomy and Astrophysics.

“Only Herschel was able to provide the sensitive spectral imaging needed to find the missing link between Jupiter’s water and the 1994 impact of comet Shoemaker-Levy 9,” said Thibault Cavalié, lead author of the paper and an astrophysicist at the Laboratoire d’Astrophysique de Bordeaux. “The asymmetry between the two hemispheres suggests that water was delivered during a single event and rules out icy rings or moons as candidate sources.

“According to our models, as much as 95% of the water in the stratosphere is due to the comet impact.”

(Image courtesy ESA/Herschel/T. Cavalié et al./NASA/ESA/Reta Beebe)