This post has been updated a few times...
Several naively employed techniques I used in Photoshop increased the contrast of this collision remnant. NASA released the original taken July 23rd by the Hubble telescope today or thereabouts. At this point the estimated size of the object which caused it is unclear. The JPL infra-red telescope in Mauna Kea displays this photo of Jupiter.
It's frustrating in that I can only find two good photos on the entire internet.
7-29 New photo
7-30 Optical photo from 7-27
7-28 Several images
8-6 Here's part of a later photo of the Jupiter impact from Donald C. Parker of Coral Gables, Florida, posted to Japan's Association of Lunar and Planetary Observers. I have flipped it (and clipped it and sharpened it) to show similar orientation to above and the public Hubble shot:
Also, compare with a near-simultaneous white cloud seen on Venus. Still some possibility of comet impact although no cometary cloud - coma - was seen in space. Best bet is still a volcano. See best pix of the Venus White Spot.
Now there is another astounding planetary impact: an unknown object smashing through one of Saturn's rings
The inset is the same image, size unchanged, with added high contrast. At the time of this writing, clicking on it opens it larger in a new window.