By Sid Perkins
Pieces of an asteroid that blasted a 70-kilometer-wide crater in southern Africa millions of years ago have been found intact within the crater, a unique discovery that defies models of such collisions.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2006/05/5854.jpg?resize=150%2C79&ssl=1)
The Morokweng crater lies beneath a 150-to-200-meter-thick layer of sand in the Kalahari Desert. Scientists detected the ancient scar a decade ago after noting anomalies in the planet’s magnetic and gravitational fields in that region, says Rodger J. Hart, a geochemist at University of the Witwatersrand in Johannesburg.