It looks like something just hit Jupiter- an SL9-like dark spot near the south pole was seen by Anthony Wesley in Australia around 13:00 - 15:00 UT on the 19th July. It looks pretty convincing to me! Apparently it wasn't there a couple of days ago.

Link to the image and report.

The clincher will be methane-band images which will reveal whether the dark spot is at low altitude (and thus meteorological) or at high altitude (and thus probably impact-generated). The NASA Infrared Telescope on Mauna Kea is planning to check it out tonight, and I'm sure there will be lots more amateur images soon.

John.

Hey, John. See this thread; Stu picked it up a few hours back. Thanks for the detailed update re Mauna Kea; any idea if Hubble's capable of being retargeted @ such short notice?

Oops, I missed Stu's thread. I'll reply there now, and this thread can be closed.