- About 66 million years ago, a 9-kilometer-wide asteroid slammed into Earth, creating the Chicxulub crater and triggering the Cretaceous-Paleogene extinction event.
- Skies filled with soot and gas, firestorms covered the planet, and global temperatures plummeted, killing 75% of life on Earth, including the dinosaurs.
- But a new study found that the asteroid was that devastating only because of where it struck.
Some 66 million years ago, a city-size asteroid slammed into Earth near Mexico's Yucatan Peninsula.
The massive impact created the 180-kilometer-wide Chicxulub crater and triggered the Cretaceous-Paleogene extinction event that wiped out 75% of Earth's biodiversity, including almost all the dinosaurs that had dominated life on land for more than 130 million years.
But that event was so devastating only because of the location the asteroid hit, a study published in the Nature journal Scientific Reports found. If it had hit elsewhere on Earth, the dinosaurs might have survived, the authors say.
The authors attribute the extinction event to the aftereffects of the impact. When the 9-kilometer-wide asteroid slammed into the planet, it caused earthquakes, triggered firestorms and massive tsunamis, and filled the air with gas and soot that caused drastic global cooling.
Another recent study found that the cooling event saw surface temperatures plummet an average of about 47 degrees Fahrenheit overnight and remain that way for years.
The new study found that the cooling event was so severe because the asteroid struck a particularly hydrocarbon-rich region and flooded the sky with soot — but that only about 13% of the planet's surface has enough sedimentary organic material and sulfur to have caused such an extreme effect.
Kaiho Oshima, Scientific Reports, 2017
In other words, if the asteroid had struck anywhere on the 87% of the planet's surface that isn't as hydrocarbon-rich, the dinosaurs might have survived. As it happened, the only dinosaurs to make it through the event were avian dinosaurs — birds. The loss of the rest created a space for mammals to thrive.
Like all theories on the extinction of the dinosaurs, this one is controversial. Most researchers attribute the extinction event to the asteroid strike, but there are various interpretations of why it was so devastating.
The authors of the recent study on the global cooling that followed the event told The Washington Post that it was gases released by the impact that caused the dramatic climate change, not necessarily soot — though they said the specific region the asteroid struck was crucial. Firestorms, toxic chemicals, and acidified oceans may have also played a role.
Other researchers have said the impact triggered an intense period of volcanic activity on the other side of the world that also would have filled the skies with sulfur and soot for years.
An asteroid striking the planet in one of the places that could have triggered these effects is an extremely-low-probability event — but one that changed the history of life on Earth, the Scientific Reports study's authors say.