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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Is Jupiter a Bodyguard or Troublemaker?
24 August 2007 (All day)
POTSDAM, GERMANY--If Jupiter were just half its mass, Earth would be a far more dangerous place. But without the giant planet, life would be pretty much the same as it is now. That's the surprising outcome, presented here today at the European Planetary Science Congress, of new computer simulations that show how Jupiter regulates the number of comets impacting our planet. According to physicist Jonathan Horner of the Open University in Milton Keynes, U.K., the common belief that Jupiter acts as a protective shield by deflecting onrushing comets needs some tweaking.
Comets are dirty chunks of ice in the outer regions of the solar system left over from the formation of the planets. A few kilometers in diameter, they can wreak havoc when they collide with Earth. But their elongated orbits can be strongly perturbed by Jupiter's gravity. In fact, the massive planet flings some comets out of the solar system altogether. That's why astronomers suggested in the early 1990s that Jupiter serves as a sort of planetary bodyguard for Earth.
But according to Horner, the matter is not so straightforward. His team's computer simulations confirm that comet impacts would be more numerous if Jupiter were less massive because fewer comets would be flung into outer space. But if there were no Jupiter at all, the researchers found, hardly any comets would whiz dangerously close to Earth. That's because Jupiter also pulls comets out of their icy reservoir in the outer realms of the solar system. As a result, the cometary impact rate on Earth wouldn't change at all if Jupiter were removed. "As soon as I heard about this, I thought, 'Yes, of course!'" says solar system dynamicist Alessandro Morbidelli of the Côte d’Azur Observatory in Nice, France.
However, don't give too much credit to Jupiter. Morbidelli points out that far more asteroids slam into Earth than do comets. Most rocky asteroids orbit the sun between Mars and Jupiter, and they probably respond very differently to changes in the mass of Jupiter. Horner's team next plans to investigate Jupiter's influence on the terrestrial impact rate of asteroids and so-called long-period comets, which arrive from far beyond the solar system.