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Billions of years ago, something slammed into the dark side of the moon and carved out a very, very large hole. Stretching 1,550 miles (2,500 kilometers) wide and 8 miles (13 km) deep, the South Pole-Aitken basin... For decades, researchers have suspected that the gargantuan basin was created by a head-on collision with a very large, very fast meteor. Such an impact would have ripped the moon's crust apart and scattered chunks of lunar mantle across the crater's surface, providing a rare glimpse at what the moon is really made of. ... Now, however... After analyzing the minerals in six...

More than 3.8 billion years ago, in a time period called the Hadean eon, our planet Earth was constantly bombarded by asteroids, which caused the large-scale melting of its surface rocks. Most of these surface rocks were basalts, and the asteroid impacts produced large pools of superheated impact melt of such composition. These basaltic pools were tens of kilometres thick, and thousands of kilometres in diameter. “If you want to get an idea of what the surface of Earth looked like at that time, you can just look at the surface of the Moon which is covered by a vast...

Date: Posted 3/4/2002 Cataclysm 3.9 Billion Years Ago Was Caused By Asteroids, Not Comets, Researchers Say WASHINGTON (February 28, 2002) -- The bombardment that resurfaced the Earth 3.9 billion years ago was produced by asteroids, not comets, according to David Kring of the University of Arizona Lunar and Planetary Laboratory and Barbara Cohen, formerly at the UA and now with the University of Hawaii. Their findings appear today in the Journal of Geophysical Research - Planets, published by the American Geophysical Union. The significance of this conclusion is that the bombardment was so severe that it destroyed older rocks on ...

..Scientists have long known that there's a mysterious amount of siderophile ("iron-loving") metals in Earth's mantle. Such metals, including gold, tend to affiliate with iron in their liquid forms. The best explanation has been that some sort of space object brought the elements to the planet just after it formed its core, but the exact nature of the impactor has been a matter of debate. Based on computer simulations, the new study says that a small number of enormous, random impacts roughly 4.5 billion years ago are the sources of Earth's iron-loving materials. These impactors were rocky objects left over...

The Late Heavy Bombardment (LHB) period is the narrow time interval between 3.8 and 3.9 Gyr ago, where the bulk of the craters we see on the Moon formed. Even more craters formed on the Earth. During a field expedition to the 3.8 Gyr old Isua greenstone belt in Greenland, we sampled three types of metasedimentary rocks, that contain direct traces of the LHB impactors by a seven times enrichment (150 ppt) in iridium compared to present day ocean crust (20 ppt). We show that this enrichment is in agreement with the lunar cratering rate, providing the impactors were comets,...