Have you ever heard of comets, asteroids and meteors? The first ever thought in your mind would come that these celestial bodies can bring massive destruction to Earth, as well as to other planets. 25 years ago, humans witnessed the first ever collision between a comet and a planet. Yes, you read it right!
It is to be noted that comets are cosmic snowballs of frozen gases, rock and dust that orbit the Sun. Comets are just one type of object that can wreak havoc on planetary bodies.
Shoemaker–Levy 9 (SL9), a comet was first discovered by Carolyn, Gene Shoemaker and David Levy in a photograph taken on March 18, 1993 with the 0.4-meter Schmidt telescope at Mt. Palomar. At the time of discovery, astronomers observed that the Shoemaker–Levy 9 had already been torn into more than 20 pieces traveling around the planet in a two year orbit.
Astronomers had argued that SL9 flew too close to Jupiter in July 1992 and was shredded due to Jupiter’s gravity. However, its true demise, came two years later, in a dramatic weeklong series of impacts from the comet's fragments.
From July 16 to 22, 1994, enormous pieces of the comet Shoemaker-Levy 9 crashed into Jupiter which created huge, dark scars in the planet's atmosphere. Astronomers, scientists and researchers across the world observed the aftermath of the 21 fragments that crashed into Jupiter's atmosphere. Each impact lofted material that splashed back into Jupiter's atmosphere, creating debris that acted as markers for scientists on Earth to study Jupiter's winds.
"Shoemaker-Levy 9 was a sort of punch in the gut," said Heidi Hammel, who led visible-light observations of the comet with NASA's Hubble Space Telescope and is now the executive vice president at The Association of Universities for Research in Astronomy AURA (which manages astronomers' interface to Hubble).
"It really invigorated our understanding of how important it is to monitor our local neighbourhood, and to understand what the potential is for impacts on Earth in the future," he added.
Interestingly, Shoemaker-Levy 9 lit up the tiny online community. In the weeklong series of impacts from the SL9 to Jupiter, NASA and other amateurs alike turned to the internet to share real-time updates about when to check in on the embattled gas giant.
"We remember that now, if we remember it at all, as sort of a big event in science — it was the first collision ever predicted beforehand between named objects in the solar system," said Dagomar Degroot, an environmental historian at Georgetown University told Space.com. "It was also a major cultural, even a political, even an environmental event," Degroot added.
He further said that nearly as many people as were hooked up to the internet at the time accessed NASA's resources about impact week. "This was really the first sort of viral event," Degroot said adding that the internet was covered by print media as well.
"That really raised the profile of the internet, and not just for the online minority but also for the offline majority … it was pretty much everywhere," Degroot concluded.
Importantly, scientists on the Earth got the opportunity to study a new celestial phenomenon due to the SL9 impact on Jupiter.
Also, it was a wake-up call that big collisions still occur in the solar system—after all, if Jupiter was vulnerable, maybe Earth is, too. If the comet SL9 would hit Earth instead of Jupiter, it could have created a global atmospheric disaster, much like the impact event that wiped out the dinosaurs 65 million years ago.