This is a composite HST image taken in visible light showing the temporal evolution of the brightest region of comet P/Shoemaker-Levy 9. In this false-color representation, different shades of red color are used to display different intensities of light.
[top panel] - This shows data taken on 1 July 1993, prior to the HST servicing mission. The separation of the two brightest fragments is only 0.3", so ground-based telescopes could not resolve this pair. The other two fragments just to the right of the closely-spaced pair are only barely detectable due to HST's spherical aberration.
[middle panel] - This shows the first HST observation after the successful servicing mission and was taken on 24 January 1994. The two brightest fragments are now about 1" apart, and the two fainter fragments are much more clearly seen. The light near the faintest fragment is not as concentrated as the light from the others and is elongated in the direction of the comet's tail.
[bottom panel] - The latest HST observation, taken on 30 March 1994, shows that the faintest fragment has become a barely discernible "puff." Also, the second faintest fragment has clearly split into two distinct fragments by March. Continued splitting events, such as those depicted here, will decrease the explosive power of any single impact into Jupiter's atmosphere as the comet makes its fiery plunge into this giant planet during the period 16-22 July 1994. Fortunately, most of the fragments of P/S-L 9 have apparently been stable for at least a year and have NOT shown any evidence for further break-up.