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10 April 2014 11:44 am ,
Vol. 344 ,
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
- 10 April 2014 11:44 am , Vol. 344 , #6180
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ScienceShot: A Late Pummeling for Earth
25 April 2012 1:20 pm
From the Mars-size object that slammed into our planet 4.5 billion years ago, forming the moon, to a bombardment that boiled off early oceans as recently as 2.5 billion years ago, Earth has taken some massive stonings in its lifetime. Now scientists think they know where the rocks were coming from. In a paper published online today in Nature, planetary dynamicists finger the now-depleted inner edge of the asteroid belt, located just outside the orbit of Mars. Researchers had previously proposed that Jupiter and Saturn wandered toward the sun about 4 billion years ago, gravitationally slinging asteroids toward Earth as they went. But new computer simulations suggest that these planets would have also flung some innermost asteroids into inclined, but not perfectly stable, orbits. Slowly, these asteroids escaped from these orbits, pummeling Earth for billions of years to come.
See more ScienceShots.