English: Closeup view of the new dark spot on Jupiter taken with Hubble's Wide Field Camera 3 on July 23, 2009.

This Hubble picture, taken on July 23, is the sharpest visible-light picture taken of the impact feature. The observations were made with Hubble's new camera, the Wide Field Camera 3 (WFC3).

The combination of the Hubble data with mid-infrared images from ground-based telescopes will give astronomers an insight into changes of the vertical structure of Jupiter's atmosphere due to the impact. The expanding spot is twice the length of the United States.

First discovered by Australian amateur astronomer Anthony Wesley, the feature is the impact site and "backsplash" of material from a small object that plunged into Jupiter's atmosphere and disintegrated.

The only other time in history such a feature has been seen on Jupiter was in 1994 during the collision of fragments from comet Shoemaker-Levy 9. The spot looks strikingly similar to comet Shoemaker-Levy 9's impact features. The details seen in the Hubble view shows lumpiness in the debris plume caused by turbulence in Jupiter's atmosphere.

The impactor is estimated to be the size of several football fields. The force of the explosion on Jupiter was thousands of times more powerful than the suspected comet or asteroid that exploded in June 1908 over the Tunguska River Valley in Siberia.

This is a natural color image of Jupiter as seen in visible light.