Theory Comet Shoemaker-Levy at Jupiter

A train of fragments, formed from the torn apart comet Shoemaker-Levy 9, impacted at Jupiter in July 1994. It was the first and only collision of the kind to be observed in the solar system ever

Comet P/Shoemaker-Levy 9 had come into a close approach to Jupiter two years before, on July 7th, 1992. It then had grazed the gas giant by a mere 0.4 Jupiter radius. From that moment onward, the comet became captured into orbit around Jupiter, as the unequal Jupiter gravitational attraction on the comet's near and far sides broke it apart. The comet was discovered in March 1993 by Eugene and Carolyn Shoemaker and David Levy. Such a disruption of a comet is an unusual event. The capture of a comet into a planetary orbit is an even more unusual one. About 21 fragments eventually composed the "comet train". They ranged in size from 0.6 to 1.2-mile (1 to 2 kilometers). All such fragments were embedded into a cloud of debris, with the material there ranging from boulders to microscopic particles. The cometary train, in May 1994, spanned 710,000 mi (1.1 million km)!

the impact of one fragment of comet Shoemaker-Levy on Jupiter night side (July 22, 1994). picture JPL

Three spacecraft had the luck to be journeying in the solar system at the moment, and well-placed to observe the shock: Voyager 2, which was leaving the solar system, the NASA/ESA's Ulysses, a Jovian and solar mission, and Galileo, a mission en route to Jupiter. The craft provided a detailed study of the collision along with Earth-based observatories, like the Hubble Space Telescope or NASA’s Deep Space Network radio telescopes

The encounter occurred from July 16 to July 22, 1994, with the fragments coming in turn to impact. Most impacts occurred on the night side of Jupiter, in the southern hemisphere, at a latitude of about 44.5°. The incoming fragments were seen to hit in 3 phases. Each fragment first came to heating up in the Jovian atmosphere. This was the "meteor phase". The fragments exploded further during about one minute, turning into fireballs of extremely hot gas ("fireball phase"). Both such phases were in fact similar to what is seen when a meteor shower is reaching the Earth's upper atmosphere. Each fragment plunged deep into the Jovian atmosphere, taking down the hot gas with them along a deep tunnel. The gas eventually was getting out, pushing debris in a mushroom-shaped, nuclear-like plume! Such plumes were reaching 236-mile (380-km) high. Such debris and the cometary and atmospheric gas -namely the "plume ejecta"- splashed back unto Jupiter's atmosphere about 6 minutes later, heating and producing intense thermal emissions. The result was these dark plages which were seen lingering in Jupiter's atmosphere during one year. Such plages were probably due to micrometer-sized carbon particles derived from the cometary or atmospheric materials. They acted just like when volcanic dust, at Earth, is powered up as far as into the stratosphere. Or such persisting dark plages might have been alternately due to sulfur erupting from a Jupiter's lower cloud layer of condensed ammonium hydrosulfide

In the year before the impact, a study team in the Air Force had been trying to convince their leadership that finding and tracking NEOs should be a part of the Air Force's space situational awareness mission. The Shoemaker announced impact became a major element in the Air Force's study of future space capabilities. By 1998, Congress—influenced by Eugene Shoemaker and other scientists advocating for NEO research- directed NASA to find 90 percent of the asteroids in our celestial neighborhood 1 kilometer or larger