A large comet or asteroid has slammed into Jupiter, creating an impact site the size of Earth, pictures by an Australian amateur astronomer show.
NASA's Jet Propulsion Laboratory confirmed the discovery using its large infrared telescope at the summit of Mauna Kea in Hawaii, said computer programer Anthony Wesley, 44, who discovered the impact zone while stargazing at home.
News of Wesley's find on a backyard 14.5-inch reflecting telescope has stunned the astronomy world, with scientists saying the impact will last only days more.
Wesley said it took him 30 minutes to realize a dark spot rotating in Jupiter's clouds on July 19 was actually the first impact seen by astronomers since a comet collided with the giant planet in July 1994.
"I thought (it) likely to be just a normal dark polar storm," he said on his website.
"However as it rotated further into view and the conditions improved I suddenly realized that it wasn't just dark, it was black in all channels, meaning it was truly a black spot," Wesley said from his home at Murrumbateman, north of Canberra.
Photographs show the impact zone, or "scar," near Jupiter's south polar region, with gases seen in infrared images.
"We are extremely lucky to be seeing Jupiter at exactly the right time, the right hour, the right side of Jupiter to witness the event. We couldn't have planned it better," NASA JPL scientist Glenn Orton told the Sydney Morning Herald newspaper.
Orton confirmed the spot was an impact site and not a localized weather event in Jupiter's swirling surface, similar to the planet's famed red spot.