There were many collisions in the early solar system. There is reason to believe that elements other than hydrogen and helium were brought to Jupiter by cometary collisions. But significant impacts within the solar system are now an extremely rare event, occurring only every few centuries.
In fact, the collision of two solar system bodies took place only in 1994. Between July 16, 1994 and July 22, 1994, the collision between the comet Shoemaker-Levy 9 and the giant planet Jupiter took place.
Named after those who discovered it
Shoemaker-Levy 9 was discovered by American astronomer Carolyn Shoemaker with her geologist husband Eugene Shoemaker and Canadian amateur astronomer David Levy. It was discovered on March 24, 1993, based on a photograph taken by the 0.4-meter Schmidt telescope on Mount Palomar. Named after its discoverers, it is the ninth short-period comet discovered by the trio.
The first comet observed orbiting a planet larger than the Sun had already broken into more than 20 pieces and was orbiting Jupiter in a two-year orbit at the time of discovery. Orbital studies confirmed that the comet passed within Jupiter’s Roche limit in July 1992, causing at least 21 fragments to be broken up by the planet’s tidal force.
While it was unusual for a comet to break into multiple fragments, observing a captured comet in orbit around Jupiter was even rarer. If that wasn’t enough, astronomers soon learned that the comet’s orbit would pass inside Jupiter in July 1994 and thus crash into the giant planet. With NASA’s spacecraft in position to watch it unfold, excitement reached fever pitch.
It proved every bit worthy as an amazing event that unfolded from July 16, 1994. NASA’s Galileo orbiter later on its way to Jupiter was able to capture the event in unprecedented detail. The comet fragments, labeled A through W, hit Jupiter’s cloud tops, beginning on July 16 and ending on July 22. Earth-based observatories and spacecraft such as the Hubble Space Telescope and Voyager 2 studied orbits.
The power of 300 million nuclear bombs
On the same day that the world’s first atomic bomb was successfully tested in 1945 as part of the Trinity experiment, comet fragments began crashing into Jupiter with the force of 300 million atomic bombs. These fragments not only created giant plumes 2,000 to 3,000 km high, but also heated the Jovian atmosphere to temperatures of 30,000 to 40,000 degrees Celsius. The comet’s impacts left dark, ringed spots on Jupiter, which were later erased by the planet’s wind.
As people around the world followed the event, it enabled scientists to learn a lot, including how the comet delivered water to Jupiter’s atmosphere. Based on many studies, this water is still there after decades.
Scientists have observed high-altitude winds on Jupiter for the first time, observing the plume of dust that floats up after the collision. Scientists studied changes in the Jovian atmosphere after the impact, as well as changes in the magnetosphere.
Furthermore, they were able to determine the structure and composition of the original comet, with calculations that it would be 1.5 to 2 kilometers across. It would be catastrophic if an object of that size ever hit our Earth. Ask the dinosaurs!