The European Space Agency has determined that the water in Jupiter’s upper atmosphere came from the impact of comet Shoemaker-Levy 9 in 1994.
Pieces of the comet hit Jupiter’s southern hemisphere in a series of spectacular collisions in July 1994. A year later, ESA launched the Infrared Space Observatory, which detected the water in Jupiter’s upper atmosphere.
The water is distributed unevenly over the planet. It is two to three times more plentiful in the southern hemisphere than in the northern hemisphere and it is only found in higher altitudes. Also, the water is concentrated around the strike zones for the comet fragments. According to the study, up to 95% of the water in Jupiter’s upper atmosphere is from comet Shoemaker-Levy 9.
Other possible sources of water had to be ruled out before the determination was certain. Water rising up from the planet’s interior is trapped in the troposphere. The water vapor could not get through a cold barrier. Jupiter’s moon Enceladus rains water onto the planet, but it does so in a more even distribution.
Jupiter image via Shutterstock