In 1993 the astronomers Carolyn and Gene Shoemaker and David Levy discovered the fragments of a comet. The comet, thereafter christened comet Shoemaker-Levy 9, had been torn apart by Jupiter’s gravitational field, and it was calculated that its approximately 21 fragments, the largest of which was half a mile wide, were headed on a collision course with the planet.
In the year 1994, between July 16 and July 22, astronomers pointed every available piece of technology at Jupiter and recorded in awe as multiple titanic explosions, each with the force of hundreds of times the nuclear arsenal of the world, generated colossal fireballs and plumes of smoke that rose nearly two thousand miles over the Jovian clouds and heated the atmosphere to temperatures of tens of thousands of degrees Fahrenheit. The explosions left dark spots on the surface of the planet the size of the Earth which would fade away over several months and provide astronomers with important information about the nature of Jupiter’s atmosphere. The event and its aftermath are described in the video below.
This event and other considerations led to the creation of the Planetary Defense Coordination Office which has as a goal to identify and track potentially hazardous objects that may come close to Earth’s orbit.