Comet Shoemaker-Levy 9 and the Jovian Impact

Shoemaker Levy - 9: The comet that slammed into Jupiter
Source: http://www2.jpl.nasa.gov/sl9/gif/sl9_home.gif

The Shoemaker-Levy comet is one of the most well-known comets in astronomy, recognized by everyone from ameteur backyard space enthusiast to the veterans at NASA. This comet showed us for the first time the immense power a comet can have if it slams into the planet.

No... Shoemaker-Levy 9 was not aiming for Earth. It's target was bigger. Much bigger. Shoemaker-Levy 9 was captured into Jupiter's orbit, and in July 1994, slammed into the gas giant. This was the first time humans had the chance to witness the destructive power of space debris left over from the early days of the formation of the solar system collide catastrophically with a planet. With nearly every ground and space-based telescope pointed towards Jupiter, we saw the comet, which had broken into 21 pieces, collide on the far side of the planet.

So, how did we know exactly when and where this comet was going to strike, in order to have enough preparation to set up so many ground based telescopes, and even the Hubble Space Telescope, to capture the impact? Well, the comet was discovered in March 1993 by David Levy, and Eugene and Carolyn Shoemaker. When the comet's orbit was mapped, it became apparent that it was, in fact, not orbiting the Sun, but rather orbiting Jupiter. Projecting the orbital calculations, it was clear that the comet would collide into Jupiter in July 1994.



Okay, so a comet is colliding into Jupiter. What is so special about that? The fact that this was the first time humans were able to witness a comet collide into another planet was a once-in-a-lifetime opportunity. It provided scientists with a look at the impact zones of where the comet his Jupiter, and see the massive scarring that it caused. It was rare to see black spots on the surface of Jupiter where the comet hit, especially since Jupiter is made up of mostly gasses. Therefore, the collision had profound impact in the study of the Jovian atmosphere, and helped scientist determine some of its chemical composition and wind speeds.


It was unfortunate that the spacecraft Galileo was still en-route to Jupiter, and was unable to capture the event up-close. However, Galileo was able to observe how the comet collision disrupted Jupiter's rings, and later caused the entire ring to tilt by 2 km. A flyby of New Horizons en-route to Pluto also showed that the ring has not fully recovered, and detected disturbances in the ring.

Watching the destructive power that a comet can have on a gas giant like Jupiter really paved the way for NASA's Near Earth Objects (NEO) program to look for and track the paths of all space rocks that could be potentially be dangerous for life on Earth. It also showed that because of Jupiter's immense gravity, it has been attracting space rocks into its orbit and shielding the inner planets from space debris since the early days of the solar system. In fact, had it not been for Jupiter attracting comets and asteroids en-route towards the inner planets, collisions might have been much more frequent on Earth, and extinction-level events such as those that killed off the dinosaurs may have been more common, to the point that complex life might never have gotten a foot-hold.