linguistic:voice_change
Jupiter

Jupiter is the most massive planet in the Solar System, and because of its large mass it has a vast sphere of gravitational influence, the region of space where an asteroid capture can take place under favorable conditions.

Jupiter is able to capture comets in orbit around the Sun with a certain frequency. In general, these comets travel some revolutions around the planet following unstable orbits as highly elliptical and perturbable by solar gravity. While some of them eventually recover a heliocentric orbit, others crash on the planet or, more rarely, on its satellites.

In addition to the mass factor, its relative proximity to the inner solar system allows Jupiter to influence the distribution of minor bodies there. For a long time it was believed that these characteristics led the gas giant to expel from the system or to attract most of the wandering objects in its vicinity and, consequently, to determine a reduction in the number of potentially dangerous objects for the Earth. Subsequent dynamic studies have shown that in reality the situation is more complex: the presence of Jupiter, in fact, tends to reduce the frequency of impact on the Earth of objects coming from the Oort cloud, while it increases it in the case of asteroids and short period comets.

For this reason Jupiter is the planet of the Solar System characterized by the highest frequency of impacts, which justifies its reputation as the "sweeper" or "cosmic vacuum cleaner" of the Solar System. 2009 studies suggest an impact frequency of one every 50–350 years, for an object of 0.5–1 km in diameter; impacts with smaller objects would occur more frequently. Another study estimated that comets 0.3 km (0.19 mi) in diameter impact the planet once in approximately 500 years and those 1.6 km (0.99 mi) in diameter do so just once in every 6,000 years.

In July 1994, Comet Shoemaker–Levy 9 was a comet that broke apart and collided with Jupiter, providing the first direct observation of an extraterrestrial collision of Solar System objects. The event served as a "wake-up call", and astronomers responded by starting programs such as Lincoln Near-Earth Asteroid Research (LINEAR), Near-Earth Asteroid Tracking (NEAT), Lowell Observatory Near-Earth Object Search (LONEOS) and several others which have drastically increased the rate of asteroid discovery.

The 2009 impact event happened on July 19 when a new black spot about the size of Earth was discovered in Jupiter's southern hemisphere by amateur astronomer Anthony Wesley. Thermal infrared analysis showed it was warm and spectroscopic methods detected ammonia. JPL scientists confirmed that there was another impact event on Jupiter, probably involving a small undiscovered comet or other icy body. The impactor is estimated to have been about 200–500 meters in diameter.

Later minor impacts were observed by amateur astronomers in 2010, 2012, 2016, and 2017; one impact was observed by Juno in 2020.