outher space...
By symontimea
@symontimea (842)
Romania
January 22, 2007 6:54am CST
A cometary bombardment during the early history of the planet is believed to have played a role in the formation of the oceans. Later, asteroid impacts are understood to have caused significant changes to the surface environment. Long term periodic changes in the orbit of the planet may also be responsible for the ice ages that have covered significant portions of the surface in glacial sheets.
will our earth cool down again?
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