Impact events on Jupiter

In modern times, numerous impact events on Jupiter have been observed, the most significant of which was the collision of Comet Shoemaker–Levy 9 in 1994. Jupiter is the most massive planet in the Solar System and thus has a vast sphere of gravitational influence, the region of space where an asteroid capture can take place under favorable conditions. Jupiter is often able to capture comets that orbit the Sun; such comets enter unstable orbits around the planet that are highly elliptical and perturbable by solar gravity. While some of them eventually recover a heliocentric orbit, others crash into the planet or more rarely become one of its satellites. In addition to the mass factor, Jupiter's relative proximity to the inner Solar System allows it to influence the distribution of minor bodies there. Dynamic studies have shown that the presence of Jupiter tends to reduce the frequency of impacts on the Earth of objects coming from the Oort cloud, while it increases the number of impacts of asteroids and short-period comets. For these reasons Jupiter has the highest frequency of impacts of any planet in the Solar System, justifying its reputation as the "sweeper" or "cosmic vacuum cleaner" of the Solar System. 2018 studies estimate that between 10 and 65 impacts per year of meteoroids with a diameter of between 5 and 20 meters (16 and 66 ft) can occur on the planet. For larger objects capable of leaving a visible scar on the planet's cloud cover for weeks, that study gives an impact frequency of one every 2–12 years. Even larger objects would strike Jupiter every 6–30 years. 2009 studies suggest an impact frequency of once every 50–350 years for an object of between 0.5 and 1 km (0.31 and 0.62 mi) in diameter; hits from smaller objects would occur more frequently. A 1997 study estimated comets 0.3 km (0.19 mi) in diameter collide with Jupiter once in approximately 500 years and those 1.6 km (0.99 mi) in diameter do so once in every 6,000 years.

About Jupiter

Jupiter is a gas giant planet with no solid surface; the lowest atmospheric layer, the troposphere, gradually changes into the planet's inner layers. The impacts of comets and asteroids generate debris fields that are progressively masked by the action of the winds, and whose significance depends upon the size of the impacting object. Human knowledge of such impacts is dependent upon direct and almost immediate observation of the event itself or of the phenomena associated with it. The cratered surfaces of Jupiter's major satellites provide information about the most ancient epochs. In particular, the discovery by the Voyager missions of thirteen crater chains on Callisto and three on Ganymede, and the evidence of the impact of Comet Shoemaker–Levy 9 (SL9), provide consistent evidence of ancient fragmentation of comets and their impacts with Jupiter and its moons. While the chains of craters observed on Earth's moon often radiate from major craters and are commonly believed to have been created by secondary impacts of the material ejected from the main collision, those present on the Jovian moons are not connected to a main crater, and it is likely they were created by the impact of a series of cometary fragments. The first evidence of impacts on Jupiter was found in the 17th century. Japanese amateur astronomer Isshi Tabe discovered among the correspondence of Giovanni Cassini's observations some drawings representing a dark spot that appeared on Jupiter on December 5, 1690, and follow its evolution over 18 days. This finding could constitute evidence of the observation of an impact on Jupiter prior to that of SL9.

Impact events

1979 impact The impact of a meteoroid on Jupiter was first captured on March 5, 1979, 17:45:24 UTC by the Voyager 1 spacecraft, which recorded a rapid flicker of light in the planet's atmosphere. Cook and Duxbury estimated that the mass of the meteoroid was about 11 kg.

1994 impacts

On July 16, 1994, the first of a series of fragments of the comet Shoemaker–Levy 9, which had broken up two years earlier, impacted Jupiter's atmosphere. The impacts had been predicted well in advance and were therefore observed by terrestrial telescopes and several space observatories, including the Hubble Space Telescope, the ROSAT X-ray-observing satellite, the W. M. Keck Observatory, and the Galileo spacecraft, which was then en route to Jupiter with a scheduled arrival in 1995. Although the impacts took place on the side of Jupiter hidden from Earth, Galileo, then at a distance of 1.6 AU (240 million km; 150 million mi) from the planet, was able to see the impacts as they occurred. Jupiter's rapid rotation brought the impact sites into view for terrestrial observers a few minutes after the collisions. Two other space probes observed the impact; the Ulysses spacecraft, primarily designed for solar observations, was pointed towards Jupiter from its location 2.6 AU (390 million km; 240 million mi) away, and Voyager 2, which was then 44 AU (6.6 billion km; 4.1 billion mi) from Jupiter, was programmed to look for radio emissions in the 1–390 kHz range and make observations with its ultraviolet spectrometer.

Astronomer Ian Morison described the impacts as following:

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