Spreading over 4,500 square kilometers (1,750 square miles) near the Gilf Kebir plateau, the craters are up to 80 meters (260 feet) deep and vary in diameter from 20 meters (66 feet) to 12.5 kilometers (7.8 miles) across.
The researchers examined 13 craters. In order to carry out microscopy and micro-spectrometry analysis, they cut thin sections from the breccias — sedimentary rock formed of angular shaped pebbles — and sandstones from the crater rims.
Paillou estimated that the field is roughly 50 million years old — relatively young in geological terms. Most of all, it is the result of simultaneous impacts.
"The impact origin is confirmed by the observation of shock-related structures, such as shatter cones and planar fractures in quartz grains of breccia," the researchers wrote in a paper published in the journal
C.R. Geoscience.
Impact crater fields result from meteor showers that can produce tens of kilometer-sized impact structures in a single event, said the researchers. Only nine impact fields are actually known on Earth.
"All known crater fields on Earth do not extend over more than 60 square kilometers (23 square miles) and can all be explained by the breakup of a single meteorite," Paillou and colleagues wrote.
Instead, the size of the Gilf Kebir field and the way the 13 studied craters are spread out indicates that it cannot be the result of the fragmentation of a single body.
"It could have been created by the fragmentation of several meteorites that encountered the Earth atmosphere," said the researchers.
They added that more field examination and modeling of the impact would be needed to support the hypothesis of a multiple strike.
"This is an important discovery," Essam Heggy from the Lunar and Planetary Institute in Houston, Texas, told Discovery News. "It also proves that radar techniques are very efficient to map large-scale subsurface features.
"Impacts fields are quite rare on Earth due to the important, different and multiple erosion processes occurring on the Earth surface," said Heggy.
"But on other planetary objects (such) as Mars, impact fields represent a much considerable portion of the surface," he said. "Imagine the benefits to apply such technique to impact craters on Mars."
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