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 on Wednesday 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, they said.

The inner solar system was filled with enormous amounts of dust after an
asteroid more than 90 miles (150 km) in diameter was struck by a smaller object
perhaps 12 miles (20 km) wide, the researchers said. It was the solar system?s
largest-known breakup 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 fertilized
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 theresearch published
in the journalScience Advances
[https://advances.sciencemag.org/content/5/9/eaax4184].

?In the last few decades, researchers have begun to understand that evolution of
life on Earth is dependent on astronomical events also,? Schmitz said.

An ancient mass extinction called the Great Dying wiped out 90% of all life on
earth. Image: Earth Archives

After noting the dinosaur-demise event caused by an asteroid perhaps 10-km 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
crab-like 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. Earth?s
climate changed from being tropical to semitropical worldwide to becoming
divided into climate zones as it is today with frozen poles and tropical
conditions at the equator.