Thursday, 25 April 2013

There's a lot of water in Jupiter's atmosphere, thanks to comet impact

There's a lot of water in Jupiter's atmosphere, thanks to comet impact, The impact of comet Shoemaker-Levy 9 into Jupiter in 1994 was a spectacular event for astronomers. The scars in Jupiter's atmosphere lasted for weeks afterward; while those have long since faded, there are still other features of the impact visible even now, it was announced last Tuesday.

Water vapour was detected during the collision itself, as the comet broke into 21 fragments which hit the atmosphere one after another in the southern hemisphere. A lot of water from the comet was released during impact as the fragments vapourized, which then became mixed in with the gases of the upper atmosphere.

In 1997, additional observations from the ESA Infrared Space Observatory (ISO) again showed water vapour, more than normal, still present in Jupiter's stratosphere. It was suspected that this was water left over from the impact although that wasn't known for sure.

But now, new and more sensitive observations have mapped out the abundance of water vapour across the planet, showing that there is stil more water vapour in the southern hemisphere than there is in the northern. These results, just published in Astronomy & Astrophysics, support the idea that this is indeed water which originally came from the comet and is still present after all these years. In fact, it is now estimated that 95% of the water vapour presently in Jupiter's atmosphere came from that cometary impact.

It's an interesting observation, given that comets are thought to have delivered at least some of Earth's water as well, when the planet was still very young. A very similar scenario may have been witnessed by human eyes for the first time, at Jupiter, not that long ago.

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