Dinosaur-Killing Asteroid May Have Had An Accomplice; New Crater Found In West Africa

An asteroid, which was credited with the extinction of dinosaurs and also the creation of the Chicxulub crater, may have had a smaller planetoid as an accomplice.

Found off the modern-day Yucatán Peninsula, the Chicxulub crater is about 66 million years old. It was reportedly formed by the asteroid, which was about 6.2 miles in diameter. Now, a new crater has been discovered formed around the same time as the Chicxulub crater, and is raising eyebrows in the paleontological community.

The researchers have named the new crater Nadir, after a nearby seamount. It was found off the West coast of Africa, probably formed by an asteroid 25 times smaller than the one that struck the Yucatán Peninsula.

David Kring, a scientist at the Lunar and Planetary Institute who was not involved in the current study but was one of the discoverers of the Chicxulub impact site, congratulated the team "for finding what looks like a probable impact crater."

"That's very important because we have so few impact craters preserved on the earth. Every single one that we can find provides a new window, new insights into the geological processes that shape them and their effects on biological evolution of Earth." Kring added.

The discovery was a serendipitous one since Uisdean Nicholson, a geologist at Heriot Watt University in the U.K., and his team had originally set out to study the tectonics that drove South America and Africa apart 100 million years ago.

Instead what they found was a structure that was circular or elliptical and was around 5.3 miles (8.5 km) from rim to rim and up to 131 feet (40 m) from floor to rim. Also, the crater's edge revealed signatures of faulting and rock deformation, and perhaps even material that jettisoned off the main crater after the impact that occurred around the same time.

The Nadir crater asteroid would have been 1,213 feet (400 m) wide — almost the size of the Empire State Building. Its impact on the ocean bed would have been equivalent to the power of 5,000 megatons of TNT and would have resulted in a fireball 6.2 miles (10 km) wide, according to the study published in the journal Science Advances.

This would have started a cascade of events -- massive amounts of water and rock would have been instantly vaporized followed by a magnitude-7 earthquake that would have set in motion submarine landslides, all of which would have produced serious waves.

At the impact site, the waves would have towered at least 1.2 miles (2 km) and the West African coastline would have witnessed waves as high as 62 miles (100 km), according to the study. Even the South American coast, which was 621 miles (1,000 km) away at the time, would have been approached by16-foot-high (5 m) tsunamis.

It is difficult to prove that the Chicxulub crater and the Nadir crater are connected without drilling into the crater floor and collecting rock samples. This is unlikely to happen in the near future since undersea drilling is a complicated and expensive affair.

Nevertheless, Nicholson added, "If money was available, drilling into that structure would be a lot of fun."