Papers coming soon. Till then, read these extracts from wiki :
It was discovered in 1993 and collided with Jupiter in July 1994, probably broke apart in July 1992 (back calculated).
It was the first active comet observed to be orbiting a planet. Was probably captured by Jupiter around 20 to 30 years earlier.
Calculations showed that its unusual, fragmented form was due to a previous closer approach to Jupiter in July 1992. At that time, the orbit of Shoemaker–Levy 9 passed within Jupiter's Roche limit, and Jupiter's tidal forces had acted to pull apart the comet. The comet was later observed as a series of fragments ranging up to 2 km in diameter. These fragments collided with Jupiter's southern hemisphere at a speed of approximately 60 km/s. The prominent scars from the impacts were more easily visible than the Great Red Spot and persisted for many months.
The discovery image of the comet appeared to show multiple nuclei in an elongated region, about 50 arcseconds long and 10 arcseconds wide.
Orbital studies of comet Shoemaker–Levy 9 soon revealed that it was orbiting Jupiter rather than the Sun, unlike all other comets known at the time. Its orbit around Jupiter was very loosely bound, with a period of about 2 years and an apoapsis (the point in the orbit farthest from the planet) of 0.33 AU. Its orbit around the planet was highly eccentric.
Tracing back the comet's orbital motion revealed that it had been orbiting Jupiter for some time. It is likely that it was captured from a solar orbit in the early 1970s, although the capture may have occurred as early as the mid-1960s.
Before the comet was captured by Jupiter, it was probably a short-period comet with an aphelion just inside Jupiter's orbit, and a perihelion interior to the asteroid belt.
The comet had apparently passed extremely close to Jupiter on July 7, 1992, just over 40,000 km above its cloud tops — a smaller distance than Jupiter's radius of 70,000 km, and well within the orbit of Jupiter's innermost moon Metis and the planet's Roche limit, inside which tidal forces are strong enough to disrupt a body held together only by gravity.
Although the comet had approached Jupiter closely before, the July 7 encounter seemed to be by far the closest, and the fragmentation of the comet is thought to have occurred at this time. The 21 fragments of the comet were named from Fragment A to Fragment W.
More exciting for planetary astronomers was that the best orbital calculations suggested that the comet would pass within 45,000 km of the center of Jupiter, a distance smaller than the planet's radius, meaning that there was an extremely high probability that SL9 would collide with Jupiter in July 1994. Studies suggested that the train of nuclei would plow into Jupiter's atmosphere over a period of about 5 days.
Astronomers estimated that the visible fragments of SL9 ranged in size from a few hundred metres (around 1,000 ft) to 2 km across, suggesting that the original comet may have had a nucleus up to 5 km across — somewhat larger than Comet Hyakutake, which became very bright when it passed close to the Earth in 1996.
The first impact occurred on July 16, 1994, when fragment A of the comet's nucleus slammed into Jupiter's southern hemisphere at about 60 km/s. Instruments on Galileo detected a fireball that reached a peak temperature of about 24,000 K / 23,700 °C, compared to the typical Jovian cloud-top temperature of about 130 K /−143 °C. It then expanded and cooled rapidly to about 1,500 K / 1,230 °C. The plume from the fireball quickly reached a height of over 3,000 km and was observed by the HST.
A few minutes after the impact fireball was detected, Galileo measured renewed heating, probably due to ejected material falling back onto the planet.
Over the next 6 days, 21 distinct impacts were observed, with the largest coming on July 18 when fragment G struck Jupiter. This impact created a giant dark spot over 12,000 km (almost one Earth diameter) across, and was estimated to have released an energy equivalent to 6,000,000 megatons of TNT (600 times the world's nuclear arsenal). Two impacts 12 hours apart on July 19 created impact marks of similar size to that caused by fragment G, and impacts continued until July 22, when fragment W struck the planet.
Chemical studies
Spectroscopic studies revealed absorption lines in the Jovian spectrum due to diatomic sulfur (S2) and carbon disulfide (CS2). Other molecules detected included ammonia (NH3) and hydrogen sulfide (H2S). The amount of sulfur implied by the quantities of these compounds was much greater than the amount that would be expected in a small cometary nucleus, showing that material from within Jupiter was being revealed (this is merely an interpretation). Oxygen-bearing molecules such as sulfur dioxide were not detected, to the surprise of astronomers.
As well as these molecules, emission from heavy atoms such as iron, magnesium and silicon was detected, with abundances consistent with what would be found in a cometary nucleus. Although a substantial amount of water was detected spectroscopically, it was not as much as predicted, meaning that either the water layer thought to exist below the clouds was thinner than predicted, or that the cometary fragments did not penetrate deeply enough.
Other observations
As predicted, the collisions generated enormous waves that swept across Jupiter at speeds of 450 m/s and were observed for over 2 hours after the largest impacts. About an hour after fragment K entered Jupiter, observers recorded auroral emission near the impact region, as well as at the antipode of the impact site with respect to Jupiter's strong magnetic field.
The cause of these emissions was difficult to establish due to a lack of knowledge of Jupiter's internal magnetic field and of the geometry of the impact sites. One possible explanation was that upwardly accelerating shock waves from the impact accelerated charged particles enough to cause auroral emission, a phenomenon more typically associated with fast-moving solar wind particles striking a planetary atmosphere near a magnetic pole.
Post-impact analysis
The size of the parent comet was calculated to be about 1.8 km in diameter (Source 1, Source 2). (This is very surprising, since the size estimate for the parent comet before fragmentation is at 5 km, mentioned under 'Predictions for the collision' section of the wiki page. It also defies the 2 km estimate of 1 fragment)
The visible scars from the impacts could be seen on Jupiter for many months. They were extremely prominent, and observers described them as more easily visible than the Great Red Spot.
Spectroscopic observers found that ammonia and carbon disulfide persisted in the atmosphere for at least 14 months after the collisions, with a considerable amount of ammonia being present in the stratosphere as opposed to its normal location in the troposphere.
Counterintuitively, the atmospheric temperature dropped to normal levels much more quickly at the larger impact sites than at the smaller sites : at the larger impact sites, temperatures were elevated over a region 15,000 to 20,000 km wide, but dropped back to normal levels within a week of the impact. At smaller sites, temperatures 10 K (10 C) higher than the surroundings persisted for almost 2 weeks. Global stratospheric temperatures rose immediately after the impacts, then fell to below pre-impact temperatures 2–3 weeks afterwards, before rising slowly to normal temperatures.
There are 13 crater chains on Callisto and 3 on Ganymede (Attributing crater chains to fragmented comets seems very wrong. Crater chains are very common in solar system & exist even on asteroids & KBO's. For fragmenting comets to cause all of them, some crazy miracles are needed).
Impact of July 19, 2009
On July 19, 2009, exactly 15 years after the SL9 impacts, a new black spot about the size of the Pacific Ocean appeared in Jupiter's southern hemisphere. Thermal infrared measurements showed the impact site was warm and spectroscopic analysis detected the production of excess hot ammonia and silica-rich dust in the upper regions of Jupiter's atmosphere. Scientists have concluded that another impact event had occurred, but this time a more compact and stronger object, probably a small undiscovered asteroid, was the cause.
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