Jupiter Both an Impact Source and Shield for Earth

August 27, 2007

Jupiter's long-standing reputation as a shield that protects Earth from comet and asteroid impacts has been cast into doubt, new research says.

Many astronomers have theorized that the gas giant's gravity deflects possible impactors, making Jupiter one of several factors that made life on Earth able to develop undisturbed.

But it turns out that if Jupiter didn't exist, some of those cometary invaders wouldn't approach Earth in the first place.

That's the early result of new computer modeling work by Jonathan Horner and Barrie Jones from the Open University in Milton Keynes, England. The research was presented last week at the European Planetary Science Congress in Potsdam, Germany.

For their study, Horner and Jones looked at the impact risk from a class of nearby bodies called centaurs, icy planetoids orbiting between Jupiter and Neptune.

"Jupiter is both a source of and shield from the risk," Horner said.

"With no Jupiter, it is much harder for centaurs to be thrown into the inner solar system, … but it is also harder for objects to be removed from the solar system."

If the presence of gas giants isn't a prerequisite for habitable worlds, astronomers could start looking at a wider range of planetary systems as hosts for alien life.

"The long-term goal of this work is to enable us to understand the question of habitability in a wider sense," Horner said.

"Working with our solar system is the obvious place to start."

Rare Earth?

For their study, Horner and Jones looked at the so-called Jupiter Family Comets (JFC), which orbit near Neptune, Uranus, and Saturn.

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