NASA - Hubble Images Suggest Rogue Asteroid Smacked Jupiter

NASA - Hubble Images Suggest Rogue Asteroid Smacked Jupiter

These NASA Hubble Space Telescope snapshots reveal an impact scar on Jupiter fading from view over several months between July 2009 and November 2009.

Credit: NASA, ESA, M. Wong, H. Hammel, I. de Pater, and the Jupiter Impact Team

Without warning, a mystery object struck Jupiter on July 19, 2009, leaving a dark bruise the size of the Pacific Ocean. The spot first caught the eye of an amateur astronomer in Australia, and soon, observatories around the world, including NASA’s Hubble Space Telescope, were zeroing in on the unexpected blemish.

Astronomers had witnessed this kind of cosmic event before. Similar scars had been left behind during the course of a week in July 1994, when more than 20 pieces of Comet P/Shoemaker-Levy 9 (SL9) plunged into Jupiter’s atmosphere. The 2009 impact occurred during the same week, 15 years later.

Astronomers who compared Hubble images of both collisions say the culprit may have been an asteroid about 1,600 feet (500 meters) wide. The images, therefore, may show for the first time the immediate aftermath of an asteroid, rather than a comet, striking another planet.

The Jupiter bombardments reveal that the solar system is a rambunctious place, where unpredictable events may occur more frequently than first thought. Jupiter impacts were expected to occur every few hundred to few thousand years. Although there are surveys to catalogue asteroids, many small bodies may still go unnoticed and show up anytime to wreak havoc.

“This solitary event caught us by surprise, and we can only see the aftermath of the impact, but fortunately we do have the 1994 Hubble observations that captured the full range of impact phenomena, including the nature of the objects from pre-impact observations” says astronomer Heidi Hammel of the Space Science Institute in Boulder, Colo., leader of the Jupiter impact study.