The onset of the Ordovician period of Earth (around 485 million years ago) saw a large decrease of marine communities due to major extinction events, with nearly 85% of marine species wiped out. For several million years, aquatic life was at its lowest.
The Great Ordovician Biodiversity Event (GOBE) changed all that. During this time, marine biodiversity exploded, establishing the modern ocean ecosystems we now know today. Plankton and reef communities diversified to a great scale while tentacled nautiloids became rising predators of this strange new world. Diversification of this scale hadn't seen since the Cambrian explosion.
For a long time, scientists have debated as to what caused this event.
Now scientists have an answer: asteroid dust. A large asteroid around 150 km in diameter called the L-chondrite parent body (LCPB) broke apart due to impact with another asteroid, a widely documented celestial event occurring around 466 million years ago, around the same period as the GOBE. This caused a large influx of L-chondrite fossil meteorites to enter the Earth's atmosphere, which continues to this day.
Research led by Birger Schmitz of Sweden's Lund University provides new evidence possibly linking this asteroid activity to dramatic weather changes, causing the GOBE and drastically changing life on Earth. A recent issue published at Science Advances said the study found that the connection lies in studying extraterrestrial micrometeorites and their elemental content.
Since these meteorites come from the same source, they have a distinct common chemical signature. One of the hallmarks of the LCPB asteroids is the presence of helium-3 isotopes, a special type of atom with one less neutron in its nucleus. Normally, this isotope has a two in one million natural abundance compared to helium-4. However, meteorites can pick up helium-3 from traveling through space, which is a crucial aspect of the study.
Several rock deposits from Sweden and Russia showed a sudden influx in helium-3 content during the GOBE, confirming extraterrestrial origins and the presence of large quantities of cosmic dust during this period. The researchers argue that the massive amounts of asteroid dust in the inner solar system effectively blocked sunlight from reaching the Earth, prompting a period of global cooling and ice age conditions. In addition, low-temperature conditions and shallower sea levels said to be caused by the LCPB–GOBE event also "fertilized" the oceans. Cold water can hold more oxygen, while lower water levels isolated some seas for life to bloom, creating better conditions in marine ecosystems than ever before.
With the threat of global warming, scientists are looking to capturing an asteroid as a source of cosmic dust to cool the Earth as a last-ditch method. However, this can easily backfire, as drastically changing ecological conditions in such a short time can create several complex effects on life, as seen with the LCPB–GOBE event.
Nevertheless, while this method might not seem feasible to mitigating global warming, this new research provides us with important insights into how we can solve one of the biggest problems of our times, as well as giving us a window as to how extraterrestrial events impact our world on a large scale.
