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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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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.