- A gigantic collision in the asteroid belt between Mars and Jupiter occurred 400 million years before the one that killed the dinos
- It triggered a mini ice age and led to a significant increase in primitive lifeform on Earth
The cataclysmic asteroid impact off Mexico’s coast that doomed the dinosaurs 66 million years ago was not the only time an astronomical event shaped the history of life on Earth.
Scientists said dust spawned by a gigantic collision in the asteroid belt between Mars and Jupiter 400 million years earlier triggered an ice age on Earth that ushered in a significant increase in marine biodiversity.
The event, occurring when life was concentrated in the seas and far before vertebrates first walked on land, set in motion evolutionary changes in invertebrates fundamental to marine ecosystems as they adapted to global cooling.
According to researchers, the inner solar system was filled with enormous amounts of dust after an asteroid more than 150km in diameter was struck by a smaller object perhaps 20km wide, the researchers said.
It was the solar system's largest known break-up event in the past 2 billion years. Solar radiation reaching Earth's surface was reduced for at least 2 million years by the dust in space and in the planet's atmosphere, said study co-author Philipp Heck, an associate curator at the Field Museum in Chicago.
Another cooling mechanism was that the iron-rich meteoritic dust fertilised large parts of the ocean surface leading to increased plankton productivity and drawdown of atmospheric carbon dioxide, added Birger Schmitz, a geology professor at Lund University in Sweden and lead author of the research published in the journal Science Advances in September 2019.
"In the last few decades, researchers have begun to understand that evolution of life on Earth is dependent on astronomical events also," Schmitz said.
After noting the dinosaur-demise event caused by an asteroid perhaps 10km wide, Schmitz added, "For the first time, scientists can now present another example of how an extraterrestrial event formed life on Earth."
The researchers found traces of dust in sedimentary rocks formed at the time containing special helium isotopes and rare minerals that revealed its extraterrestrial origin.
Invertebrate groups that experienced diversification included horseshoe crablike trilobites, clams, clam-like brachiopods and a group called gastropods that included snails and slugs.
The cooling event unfolded gradually, enabling marine life during the Ordovician Period to adapt, unlike the sudden impact that erased the dinosaurs from the planet.
Earth's climate changed from being tropical to semi-tropical worldwide to becoming divided into climate zones as it is today with frozen poles and tropical conditions at the equator.