Collisions between planets and smaller objects, such as asteroids and comets, have played an important role in shaping the solar system. Jupiter’s powerful gravitational field has protected Earth from potentially catastrophic impacts, either swallowing such objects or flinging them to distant corners of the solar system. At the same time, Jupiter has undoubtedly directed some chunks of rocks or ice toward Earth, seeding our planet with elements needed for life and, occasionally, killing life. For example, a comet impact most likely wiped out the dinosaurs 65 million years ago.
Although frequent early in the solar system’s history, these kinds of impacts are now relatively rare. But in 1994, the world witnessed an unprecedented event when comet Shoemaker-Levy 9 careened toward Jupiter. Astronomers had known about this rendezvous ahead of time and so were able to prepare, pointing as many telescopes as they could toward the gas giant.
When the comet approached Jupiter, it had broken up into more than a dozen fragments. During an earlier orbit around the Sun, the comet probably strayed too close to Jupiter and the planet’s gravity pulled it apart. Everyone watched as pieces of the comet slammed into Jupiter’s clouds, creating a string of giant, glowing plumes.
Collisions like this don’t happen all the time, but they do pose a real threat to our own planet. It’s therefore important to understand how often impacts occur. In fact, two more objects crashed into Jupiter in 2009 and 2010 – and these collisions weren’t noticed until after the fact.
Comet Shoemaker-Levy 9 left dark scars that helped us to better understand Jupiter’s atmosphere.
Armed with sophisticated equipment, amateur astronomers are now monitoring Jupiter, improving the likelihood of spotting impacts.
The 1994 impact was an exciting lesson, but also a warning.