Morokweng impact structure

The Morokweng impact structure is an impact structure buried beneath the Kalahari Desert near the town of Morokweng in South Africa's North West province, close to the border with Botswana.

Description
The impact structure is at least about 75-80 km in diameter and the age is estimated to be 146.06 ± 0.16 million years, placing it within the Tithonian stage of the Late Jurassic, several million years before the Jurassic–Cretaceous boundary. Discovered in 1994, it is not exposed at the surface, but has been mapped by magnetic and gravimetric surveys. Core samples have shown it to have been formed by the impact of an L chondrite asteroid estimated to have been 5 to 10 km in diameter.

In May, 2006, a group of scientists drilling into the site announced the discovery of a 25 cm-diameter fragment of the original asteroid at a depth of 770 m below the surface, along with several much smaller pieces a few millimetres across at other depths. This discovery was unexpected, since previous drillings on large impact structures had not produced such fragments, and it was thought that the asteroid had been almost entirely vaporised. Some of the fragments can be seen in the Antenna Wing of London's Science Museum.