ESA Discovers Origin Of Jupiter's Mysterious Atmospheric Water
April 23, 2013

ESA Discovers Origin Of Jupiter’s Mysterious Atmospheric Water

Lee Rannals for — Your Universe Online

The European Space Agency (ESA) says it has unraveled the mystery as to the origin of water observed in the upper atmosphere of Jupiter.

ESA's Herschel space observatory found evidence that the water in this part of Jupiter's atmosphere was delivered by the dramatic impact of comet Shoemaker-Levy 9 in July 1994. During this collision, a string of 21 comet fragments pounded into the southern hemisphere of Jupiter, leaving dark scars in the planet's atmosphere for several weeks.

This event was the first direct observation of an extraterrestrial collision in the Solar System. Astronomers throughout the world followed the collision with ground-based telescopes.

A year after the collision, ESA's Infrared Space Observatory (ISO) was launched and it was the first spacecraft to detect and study water in Jupiter's upper atmosphere. Although scientists speculated that Shoemaker-Levy 9 was behind the origin of this water, direct evidence was missing. Scientists were able to prove that the water was not from within the planet, but solidly determining its origin took 15 years.

ESA said its Herschel spacecraft used sensitive infrared vision to map out the vertical and horizontal distribution of water's chemical signature. These observations found two to three times more water in the southern hemisphere of Jupiter than in the northern hemisphere.

“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,” Thibault Cavalié of the Laboratoire d´Astrophysique de Bordeaux, said in a statement. “According to our models, as much as 95 percent of the water in the stratosphere is due to the comet impact.”

Another source of the water would be from steady rain of small interplanetary dust particles onto Jupiter. However, if this was the case, the water would be uniformly distributed across the whole planet.

Scientists also thought that one of Jupiter's ice moons could have delivered water to the planet through giant vapor torus. Herschel has witnessed an event like this from Saturn's moon Enceladus, however scientists have ruled this possibility out on Jupiter because none of Jupiter's large moons are in the right place to deliver water to the location observed.

After ruling out all of the other possible scenarios, scientists were left with Shoemaker-Levy 9 as being the only likely culprit.

“All four giant planets in the outer Solar System have water in their atmospheres, but there may be four different scenarios for how they got it,” said Dr Cavalié, lead author of the paper published in Astronomy and Astrophysics.. “For Jupiter, it is clear that Shoemaker-Levy 9 is by far the dominant source, even if other external sources may contribute also.”

Göran Pilbratt, ESA´s Herschel project scientist, said that Herschel's observations have linked a unique comet impact to Jupiter's water, "finally solving a mystery that has been open for nearly two decades."

ESA said this study foreshadows those planned for its future Jupiter Icy moons Explorer mission, which will launch in 2022. This mission will map the distribution of Jupiter's atmospheric ingredients in even greater detail.

Jupiter's moons are still a bit of a mystery to scientists, but plenty of theories surround them. Scientists recently wrote in the Astrophysical Journal Letters that Jupiter's moon Europa may contain building blocks of life. The researchers said this moon may have enough hydrogen peroxide on its surface to support life, if it was to mix with the ocean trapped beneath its icy surface.