Space Dust Says: Earth was Completely Covered in Ice |
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Written by spacetravel.org
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Space dust found deep below central Africa has lent credence to the controversial Snowball Earth theory. This theory states that the Earth was entirely frozen about 630 million years ago. Many geoscientists favor the Slushball Earth theory, which states that while the Earth did become significantly colder at that time, the equatorial oceans remained unfrozen.
To compare the two theories, Bernard Bodiselitch of the University of Vienna and his colleagues measured the levels of iridium, a component of the space dust that constantly falls on Earth, in three cores drilled from central Africa. They predicted that if the equatorial oceans never froze, the iridium would have settled gradually on the equatorial sea floor, but if the equatorial oceans had frozen, the iridium would have accumulated on top of the ice, then precipitated all at once when the ice melted.
Bodiselitch and his team found a sharp spike in iridium levels in the cores, which dated to the end of the cooling period. This favors the snowball theory. The size of the spike suggests that the Earth was covered in ice for a period of between 3 and 12 million years.
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