During the morning of September 10th (11:35 UT) there was a visual sighting of an apparent fireball on Jupiter.
The fireball was probably caused by a small asteroid or comet hitting the surface of Jupiter. Similar impacts were observed in June and August 2010. An analysis of those earlier events suggests that Jupiter is frequently struck by 10 meter-class asteroids–one of the hazards of orbiting near the asteroid belt and having such a strong gravitational pull.
Several amateur astronomers witness the explosion. Dan Peterson Racine from Oregon saw it first through his Meade 12” LX200 telescope.
“It was a bright white flash that lasted only 1.5 – 2 seconds," he reports.
Petersen reported it to Richard Schmude of the Association of Lunar and Planetary Observers (ALPO). From the time and position given, the flash was on the North Equatorial Belt at approximately L1=335, L2=219, L3=257.
On the Cloudy Nights astronomy forum, Petersen described his sighting:
This morning (9/10/2012) at 11:35:30 UT, I observed a bright white two second long explosion just inside Jupiter’s eastern limb, located at about Longitude 1 = 335, and Latitude = + 12 degrees north, inside the southern edge of the NEB. This flash appeared to be about 100 miles in diameter. I used my Meade 12″ LX200 GPS telescope and a binoviewer working at 400X for the observation, seeing was very good at the time. I was thinking about imaging Jupiter this morning but decided to observe it instead, had I been imaging I’m sure I would have missed it between adjusting webcam settings and focusing each avi. We’ll have to wait and see if a dark spot develops inside the southern regions of the NEB over the next day or two. Good luck imaging this. My best guess is that it was a small undetected comet that is now history, hopefully it will sign its name on Jupiter’s cloud tops.
Another amateur astronomer, George Hall of Dallas, Texas, was video-recording Jupiter at the time, and he confirmed the fireball with the screenshot (above) from a video.
Astronomers around the world will now begin monitoring the impact site for signs of debris–either the cindery remains of the impact or or material dredged up from beneath Jupiter's cloud tops. Some impacts do produce such debris, while others don't. Researchers aren't sure why; perhaps this event will provide some clues.