Space

IT'S the Superman of space rocks. A mysterious meteorite that crashed to Earth last year may have been the toughest of its kind.

The Carancas meteorite struck the town of that name in Peru last September, blowing a hole in the ground 13 metres wide. The fact that locals saw a single object strike suggests a meteorite made of iron, like the one that created a similar crater in 1990 in Sterlitamak, Russia, because stony meteorites normally fragment high above the Earth and spread relatively harmlessly over a wide area. However, the debris found by investigators was stone.

One explanation for this conundrum, though at odds with the eyewitness accounts, is that the object broke into smaller pieces which hit the ground together. Another theory is that the meteorite was one of many chunks from a larger, slow-moving object which broke up when it met the atmosphere at a glancing angle. Yet all these chunks would probably have been travelling too slowly to create the Carancas crater.

Now Pavel Spurný and colleagues at the Astronomical Institute of the Academy of Sciences of the Czech Republic argue that the object could have survived the descent intact if, by a one-in-a-million chance, it lacked internal cracks and irregularities. Using estimates from other groups of the meteorite's trajectory, velocity and impact energy, Spurný and colleagues built a computer model showing that an object around 1 metre across could enter the atmosphere at a relatively fast 20 kilometres per second and survive the descent if it was free of cracks (Astronomy & Astrophysics, vol 485, p L1).

Jay Melosh, a geophysicist at the University of Arizona in Tucson, doubts Spurný's theory. He says stone fragments found at the scene are so soft that they crumble to the touch, so the object was probably made of rock held together by iron - which is yet to be found.

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