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24 April 2014 11:45 am ,
Vol. 344 ,
Major climate data sets have underestimated the rate of global warming in the last 15 years owing largely to poor data...
The tsetse fly is best known as the vector for the trypanosome parasites that cause sleeping sickness and a disease in...
The National Institutes of Health is revising its "two strikes" rule, which allowed researchers only one chance to...
By stabilizing the components of retromers, molecular complexes that act like recycling bins in cells, a recently...
Fossil fuels power modern society by generating heat, but much of that heat is wasted. Semiconductor devices called...
Researchers are gaining insights into what made Supertyphoon Haiyan so powerful and devastating through post-storm...
Millions around the world got a first-hand look at what it was like to be in Tacloban while it was pummeled by...
- 24 April 2014 11:45 am , Vol. 344 , #6182
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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.
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