Monday, August 10, 2009

Earth's oceans may have been created by 'comet swarm'

One of Pound360's favorite mysteries is how the Earth ended up with so much water. A recent study by the Niels Bohr Institute in Denmark suggests tens of thousands of comets, which pummeled the earth in a giant swarm 3.85 billion years ago, are to thank.

This is the second recent study to suggest the oceans were created during the mysterious "Late Heavy Bombardment" (LHB) which sprayed the Earth and Moon with loads of meteors, comets or something about 3.85 billion years ago. Earlier this year,
an Imperial College London study said it was meteors during the LHB.

So was it comets or meteors? The Denmark study says comets due to iridium levels in Greenland rocks that date back to the time of the LHB. Iridium levels there are low, suggesting there weren't many asteroids back then. Asteroid impact craters typically have iridium levels around 18,000 parts per trillion, while comet craters only show 180 parts per trillion (that's because their mostly water and ice).

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I started pound360 to channel my obsession with vitamins, running and the five senses. Eventually, I got bored focusing on all that stuff, so I came back from a one month hiatus in May of 2007 (one year after launching Pound360) and broadened my mumblings here to include all science.