Comet water in Jupiter's atmosphere
The crashing of Comet Shoemaker-Levy 9 into Jupiter in July 1994 was a spectacular event seen by thousands around world -- the first time that anyone has watched two solar system bodies colliding.
The scar of that collision was visible on Jupiter for weeks afterward but astronomers wanted to know what the long-term effects of the collision were. In 1997, the European Space Agency's Infrared Space Observatory detected a lot of water in Jupiter's upper atmosphere. There is usually little water so high above Jupiter, but was it from Shoemaker-Levy 9?
There are other possible water sources, including interplanetary dust and one of Jupiter's many satellites. Astronomers couldn't tell. But ESA's Herschel Space Observatory, launched in 2009, has now settled the issue.
A team from the Bordeaux Astrophysics Laboratory in France used Herschel to observe Jupiter's atmosphere.
With its superior resolution it could map the distribution of water and found that the majority was in the southern hemisphere (where the comet hit) and its abundance peaked at 44°S, the same latitude as the comet impact.
The researchers concluded that 95% of the water detected in Jupiter's stratosphere is from Shoemaker-Levy 9.
The results are interesting because they help researchers understand how material was spread around the solar system by comets during its infancy, when there were very many more comets flying around.
Earth, in particular, seems to have much more water than you would expect and some think it was dumped on earth by snowy comets.