Jupiter, Taking One for the Team

By Ed Martinez

September 21, 2009

On July 19, an Australian amateur astronomer discovered a new dark spot on Jupiter. The new “battle scar” apparently was caused by an asteroid or comet about 24 hours preceding its discovery. According to scientists, this spot, as well as others, highlight the planet’s role in our solar system. 

Jupiter has a very powerful gravitational field, which helps protect the Earth and other planets from such impacts. "Jupiter is the big bully of the solar system," said MIT professor of planetary science Richard Binzel, who specializes in observations of asteroids and comets. But if it's a bully to some celestial objects, it's the protector of others. "Under Jupiter's influence, many objects end up being cast into the sun, some get cast out of the solar system, and some end up striking Jupiter itself. The net result is that Jupiter keeps the inner solar system more cleaned out than it might otherwise be."

Binzel has written extensively about celestial objects impacting planets, and has focused on bringing awareness to the risk of possible impacts on Earth by newly discovered asteroids or comets.

This new discovery was a surprise to Binzel. “We had no idea these kinds of impacts might be so frequent," he said, adding that the new question is whether having two impacts on Jupiter within 15 years—after centuries of observations in which no such impacts were seen—is just a coincidence, or a result of our ever-improving ability to observe and detect such events.