When the comet Shoemaker-Levy 9 (SL9) hit Jupiter in the summer of 1994, it may have left more than visible scars on the Jovian surface, according to a new study published in Astronomy and Astrophysics.

Although emission from water vapor was observed during the fireball phase of the SL9 impacts, scientists had a hard time assessing how this would affect the planet’s composition in the long run.

Furthermore, while scientists detected water vapor in the planet’s stratosphere in 1997, there was never any conclusive evidence that it was carried there by the comet. Other possibilities included interplanetary dust particles, asteroid collisions, icy rings or one of its 60 satellites.

One source that was never considered is internal one. This was an impossibility, scientists said, due to the “cold trap” that separates the stratosphere from the visible cloud deck in the troposphere below.

Now, almost 20 years after the collision, astronomer Thibault Cavalie and colleagues have observed a telling clear north-south asymmetry in the distribution of water, with more of it occurring in the south. What’s more, the highest concentration of water focuses around the sites of the 1994 comet impact and is only found at high altitudes.

Should the rain be the result of steady “rain” of small dust particles, the scientists argue it would be uniformly distributed across the whole planet and would have filtered down to lower altitudes.

Furthermore, the team reports, none of Jupiter’s large moons are in the right place to deliver water to the locations where it’s currently found.

“According to our models, as much as 95 percent of the water in the stratosphere is due to the comet impact,” Cavalie said in a press release.

The discovery, he said, wouldn’t have been possible without the European Space Agency’s Herschel space observatory.

“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,” he said.