Compared to the Chicxulub crater on the sea floor off Mexico’s Yucatan Peninsula, the newly discovered crater off the West African coast is quite small. Its diameter is only about 8.5 kilometers compared to the 180 kilometers for the impact site on the other side of the Atlantic. But the find, which Uisdean Nicholson from Heriot Watt University in Edinburgh and his team describe in “Science Advances”, could help explain the end of the Cretaceous period 66 million years ago.
With the help of seismic reflection data from the subsurface in the Atlantic off West Africa, the working group discovered the crater, which has been covered by a 300 to 400 meter thick layer of sediment since the impact. The corresponding age dating suggests that the impact may have taken place at most a million years after Chicxulub – and possibly even immediately after the larger impact. According to Nicholson and Co, the nadir structure in the sea floor has the typical features of an asteroid crater, for example a central elevation, which would not be found if an underground magma chamber collapsed.
The most likely explanation is therefore an asteroid with a diameter of about 400 meters, which shot into the sea, which was only 800 meters deep at that point. Objects of this size have hit the Earth regularly in the past; the temporal proximity to Chicxulub could therefore also be pure coincidence. However, they may have hit Earth at practically the same time because it was a binary asteroid. A previous hit in space may have struck Chicxulub and ripped it in two unequal parts. Earth’s gravity could have done this as well before the chunks crashed onto the planet. After all, it is estimated that 14 percent of the craters on Venus come from binary asteroids, while on Earth only 2 to 4 percent are known to date.