Scientists have discovered an impact crater off the coast of Guinea in West Africa that is giving rise to question whether the asteroid that wiped out the dinosaurs had a smaller sibling that struck around the same time. According to New York Times, the crater was created 66 million years ago, around the same time another one slammed into the Earth’s surface leaving a massive crater underneath the sea. The NYT report said researchers are still trying to determine the exact age of the crater.

The crater it is being compared to Chicxulub, the 100-mile-wide chasm which according to NYT was formed by a six-mile asteroid that caused global devastation and ended the age of dinosaurs.

The researchers have named the other crater as Nadir. According to the BBC, it is more than 300 metres below the seabed, some 400 km off the coast of Guinea.

The crater’s diametre is 8.5 kilometres, the BBC report said, adding that it was identified by Dr Uisdean Nicholson from Heriot-Watt University, Edinburgh, UK.

He discovered the crater while analysing the seismic survey data for another project to understand past climatic changes on Earth.

“These surveys are kind of like an ultrasound of Earth. I’ve spent probably the last 20 years interpreting them, but I’ve never seen anything like this,” he told the BBC.

Dr Nicholson now wants to drill into the crater and examine the minerals from the floor to ensure that it was indeed caused by an asteroid strike.