Anthony Wesley, who hails from Canberra, Australia, grabbed this shot of a new dark spot near the south pole of Jupiter. The great thing about astronomy is it's one of the last areas in science where 'amateurs' can still do great things before Big Science gets to it.
Nancy Atkinson at Universe Today says it's similar to the marks left by Comet P/Shoemaker-Levy 9 15 years back while Phil Plait at Discover says it's likely just weather.
Moon shadow? Nope, wrong place and wrong size, says Wesley.
Preliminary image showing a black mark in Jupiters South Polar Region (SPR) which is almost certainly the result of a large impact - either an asteroid or comet - similar to the Shoemaker-Levy 9 impacts in 1994. Image captured by Anthony Wesley on 19th July 2009 at 1554UTC from Murrumbateman Australia
What say you? We'll find out more in the next day or two but kudos to Wesley for being there first with his swanky new 14.5" Newtonian.
See it yourself soon:
2009 Jul 20 02:00 ( 216°)
2009 Jul 20 11:56 ( 216°)
2009 Jul 20 21:52 ( 216°)
2009 Jul 21 07:47 ( 216°)
2009 Jul 21 17:43 ( 216°)
For even more times when this dark spot on Jupiter will be visible, see Mike Salway's blog.
For JPL's analysis of what it was, see the next post Dark Spot On Jupiter: New Impact 15 Years After The Last One.