In 2008, Italian mineralogist Vincenzo De Michele spotted Egypt’s 148-foot Kamil Crater while scanning Google Earth; scientists later recovered 1.7 tons of meteorite fragments

Vincenzo De Michele wasn’t looking for a meteorite crater. The Italian mineralogist, a former curator at Milan’s Natural History Museum, was scanning satellite images on Google Earth in 2008, looking for signs of ancient human settlements in Egypt’s southern desert. But his eyes fell on a near-perfect circle cut in the sand near the junction of Egypt, Sudan and Libya. Later, a study, ‘The Kamil Crater in Egypt,’ in the journal Science by geologist Luigi Folco and his team confirmed that circle as one of the best-preserved impact craters ever found on Earth.

A crater in the desert

The crater De Michele found is 148 feet across, with a raised rim about 10 feet above the desert floor. The paper's supporting data put the true floor depth at 52 feet below the rim, but because of sand accumulation due to winds in the region, the floor is presently about 33 feet below the rim. Folco's team named the site Kamil Crater after Gebel Kamil, a rock outcrop about 65 kilometers northeast of the site and the only named landmark nearby. It sits in the East Uweinat district of southwestern Egypt, a flat, rocky plain that has changed little over time.

An iron visitor from the sky

The crater was formed by neither wind nor water. The Science paper explains that it was caused by an iron mass measuring about 4 feet across and weighing 10 tons. Researchers modeled the impact assuming an average meteoroid entry velocity of about 18 kilometers per second as it first hit the atmosphere; by the time it struck the ground, atmospheric drag had slowed it to an actual impact velocity of about 3.5 kilometers per second. Scientists traced the object's path in a later study led by Massimo D'Orazio in the journal Meteoritics and Planetary Science and found it came in from the northwest along a fairly steep approach, hitting the ground at an angle of about 30 to 45 degrees. What was unusual about the impact was that this iron mass didn't burn up or break apart high in the atmosphere, as most incoming space rocks do. It held together for the most part on the way down, and then burst on hitting the ground.

Thousands of fragments, one giant survivor

After more than a year of planning, a geophysical expedition arrived at this remote location in February 2010. Teams scoured the crater and desert around it on foot, collecting every piece of metal they could find. In the Science paper, scientists cataloged 5,178 individual meteorite fragments, weighing a total of about 1.71 tons. The vast majority were shrapnel weighing less than 34 kg per piece, with one notable exception: a single 83 kg piece which was found intact and largely undamaged. The D’Orazio paper also classified the meteorite. It is an “ungrouped” iron meteorite known as Gebel Kamil, which does not really belong to any known meteorite group. It contains an unusual amount of nickel, nearly 20 percent by weight, with high concentrations of germanium and gallium, giving scientists information about its possible point of origin.

A rare natural laboratory

Earth has only 176 confirmed impact craters, and as the Science paper notes, only 15 of those are smaller than 984 feet across, as small craters tend to erode or get buried within a few centuries. Kamil had survived almost untouched, providing scientists with a new, physical specimen to compare to computer models they had used for years. That real-world data challenged a long-standing assumption. Physicists had almost always thought that iron bodies of a certain size and greater would fall apart before hitting the surface. The authors of the Science article added Kamil's findings to the existing database and calculated that nearly 35 percent of all iron meteorites of that size category survive atmospheric entry more or less in one piece, a result they said still needs further testing.

A window onto other worlds, right here on Earth

Kamil still shows faint traces of bright rays extending from its rim, remnants of rock blasted outward during the impact. The formation of rayed craters like this is very common on the surfaces of the Moon and Mars because there are no winds or rains to erase their features. Researchers said that a well-preserved rayed crater like Kamil had rarely been seen before on Earth. That was one of the reasons why Kamil was so significant for the planetary scientists. It gave scientists the chance to study, up close and on solid ground, a kind of impact scar they had mostly only seen through telescopes pointed at other worlds. Not bad for a discovery that began with someone looking for an entirely different thing.