The second space rock hit Earth after the one that killed the dinosaurs


About 66 million years ago, the Earth took a punch, according to a new study.

First, a 6 mile wide space rock hit present day Mexico. The impactor, named Chicxulub, contributed to the disappearance of dinosaurs, as well as 50 to 75% of life on Earth.

Then, 650,000 years later, a 1.5 mile asteroid known as the Boltysh struck. The rock carved out a 15-mile-wide crater in what is now central Ukraine.

Scientists once believed that Boltysh and Chicxulub contributed to the mass extinction that doomed the dinosaurs. But according to study published in the journal Science Advances on Friday, Boltysh likely had an impact on Earth long after the last victims of the extinction disappeared.

“I think the extinction was basically over and dusted off” by the time Boltysh struck, Annemarie Pickersgill, a University of Glasgow meteorite impact researcher and co-author of the new study, told Insider.

While Boltysh is unlikely to have exacerbated the mortality, Pickersgill said the second impact may have delayed Earth’s recovery after the catastrophic extinction.

Analysis of rocks that melted during the Boltysh impact

Melt rock from boltysh ukraine impact site

A shocked piece of quartz from the Boltysh impact crater in Ukraine.

Martin Schmieder / Wikimedia Commons

Scientists discovered the impact of Boltysh in 2002, and a first study suggested that the asteroid had struck 2,000 to 5,000 years before Chicxulub.

Pickersgill said her team intended to date Boltysh Crater more accurately, but they didn’t expect their findings to upset previous research.

“I was surprised to find out that Boltysh’s age was after Chicxulub,” she said.

The researchers first analyzed two samples from the deepest part of the crater, more than a third of a mile underground. The heat from the asteroid impact had melted the rocks, so dating them allowed Pickersgill to recover when Boltysh struck.

Next, the team looked at samples from a sediment layer in Montana that coincided with the Chicxulub impact. Using radiometric dating – a technique that determines how long it takes for radioactive material to decay in rocks – the team determined that the Boltysh rocks had melted about 650,000 years after the Chicxulub strike.

Boltysh may have contributed to an explosion in global warming

Chicxulub_impact asteroid

This painting depicts an asteroid hitting the shallow tropical seas of the sulfur-rich Yucatan Peninsula in what is now southeastern Mexico. The consequences of this massive asteroid collision, which occurred around 65 million years ago, are said to have caused the extinction of dinosaurs and many other species on Earth.

Donald Davis / NASA

The updated age for Boltysh Crater coincides with a period of intense global warming known as lower C29 hyperthermia, the study’s authors said.

During a hyperthermal event, which can last for up to 40,000 years, global average temperatures can rise by 5.4 degrees Fahrenheit (3 degrees Celsius).

Pickersgill’s team has yet to determine whether the asteroid caused the hyperthermia.

But she said there is evidence to suggest that Chicxulub first cooled Earth’s climate, then warmed it.

When the dinosaur-killer rock struck, it threw a cloud of dust, sulfur and carbon dioxide into the atmosphere. This gaseous haze blocked the sun for a few decades, a study suggests, cooling the Earth.

During these few decades, most of the terrestrial and marine species on Earth have disappeared.

Eventually, the Chicxulub cloud dissipated, and the sulfur and carbon left in the atmosphere – which trap heat on the Earth’s surface – began to warm the planet.

But once Boltysh struck, that impact may have released additional gases into the air and exacerbated that warming. This could have made it more difficult for terrestrial species to recover after mass extinction.

Research suggests that it took 9 million years to bring the number of different species in North America back to pre-Chicxulub levels.


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