Astronomers have been studying the presence of water in the stratosphere of Jupiter for a long time. Now, thanks to the use of ESA’s Herschel Space Telescope, a team believe they have found evidence that this water was brought by the comet Shoemaker-Levy 9, which crashed into the planet in 1994.

The collision of comet Shoemaker-Levy 9 with Jupiter was a show that catalyzed the attention of astronomers around the world but also of ordinary people fascinated by a truly extraordinary event. The powerful gravity of the planet broke the comet into 21 pieces during its approach so actually there was a series of impacts that followed over the course of about a week.

In 1995, the space probe Infrared Space Observatory (ISO) studied Jupiter’s atmosphere and detected the presence of water in the stratosphere. From the beginning, scientists hypothesized that it was brought by comet Shoemaker-Levy 9 but at the time there was no evidence. It was only possible to exclude that the water was rising from the underlying layers of the atmosphere because the vapor can’t pass through what is a kind of cold trap that separates the stratosphere from the troposphere below.

That water must have come to Jupiter from outside but it was necessary to wait to have a sophisticated instrument for infrared observations such as the Herschel Space Telescope to create a map of its distribution. Now it’s been possible to establish that in Jupiter’s southern hemisphere there’s an amount of water two to three times higher than in the northern hemisphere and the highest concentration is in the vicinity of the sites where the fragments of Comet Shoemaker-Levy 9 crashed.

Thibault Cavalié of the Laboratoire d’Astrophysique de Bordeaux, the main author of the article published in “Astronomy and Astrophysics” that illustrates this research, points out that according to the models of the scientists who conducted the study up to 95% of the water in the stratosphere was brought by the comet.

The remaining traces of water are probably originated by a kind of interplanetary rain of various materials that fall on Jupiter. This water is spread evenly over the entire planet. Instead, it was ruled out that the water could come from one of Jupiter’s satellites because none of them is in a position to deliver it to the areas in which it was observed.

In recent years, some impacts of entities much lower than that of comet Shoemaker-Levy 9 have been observed on Jupiter but again it was possible to exclude that a significant amount of water has been brought to the areas where it’s concentrated.

In short, the comet Shoemaker-Levy 9 is the only possible source of all that water in those areas. It was an interesting mystery from the astronomical point of view but it’s important because it also gives us an idea of ​​how much water can be brought by a comet. It’s possible that in the distant past many comets have hit the Earth bringing most of the water present today and maybe even aminoacids, which are the building blocks of life forms.

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