clipped from: space.newscientist.com   

Last year's meteorite impact in Peru has puzzled scientists. Fragments found at the site reveal the impactor was a stony meteorite, but stony meteorites usually shatter when they hit the Earth's atmosphere, raining many small pieces over a wide area.

So how could the meteorite make it all the way to the ground and gouge out a 15-metre-wide crater, such as the one found in the Peruvian town of Carancas?

Like stony meteorites, glass beads break apart when travelling at high speeds through the air, experiments show (left). But under the right conditions, the fragments can stay together in a dense swarm that can still gouge a crater on the ground (right) (Image: Peter Schultz et al/Brown U)

The answer, says a team of scientists, may be that the original meteorite did break up when it slammed into the atmosphere, but then a shock wave formed around the fragments as they fell to Earth. This shock wave acted as a barrier that kept the pieces together so they could blast out a crater on impact.