Nav: Home

Myth busted: No link between gigantic asteroid break-up and rise in biodiversity

January 24, 2017

Some 470 million years ago, during the middle part of the geological period known as the Ordovician, an asteroid collision took place somewhere between Mars and Jupiter. The collision caused an explosion that sent a cascade of meteorites towards Earth. The heavy bombardment of Earth continued for millions of years, and even today some 20% of all meteorites that reach Earth originate from this asteroid break-up. At the same time the Earth witnessed the greatest rise in marine biodiversity since the origin of multicellular life. So, the question is: was there a connection between these two fundamental events in Earth history, as has been proposed? A new study now demonstrates that the rise in biodiversity commenced long before the asteroid collision.

The link between these two fundamental events -- the so-called Ordovician radiation and the sustained meteorite bombardment -- has, for many years, presented a paradox in science. We are used to hearing the story of meteorite impacts that leads to the loss of species richness, such as when the dinosaurs went extinct 65 million years ago. But could the opposite scenario be a possibility as well? asks Assistant Professor Christian M. Ø. Rasmussen from the Natural History Museum of Denmark rhetorically. He is co-authoring the study in which an incidental finding of the rare mineral zircon within the meteorite-bearing rock layers led to an answer to the paradox.

Plus, minus 6 million years

Researchers have long known that the fossil meteorites are lying in rock layers that also witness the great increase in biodiversity, but could only date the asteroid break-up to occur within a time frame of 12 million years. This interval exactly overlaps the initiation of the great biodiversity increase. But, with the lucky finding of zircons in rock layers also containing fossil meteorites, the researchers suddenly had the opportunity to precisely determine when the asteroid collision took place, and thus, whether there was a link to the radiation event, or not.

-Zircons are special as they can be used to date rocks. They come from magma chambers in the crust but are extruded onto the Earth's surface through volcanic eruptions. Thus, if you find zircons in the rock record you can date these zircons and thus get an age for when this eruption took place. In this case, this date would also define a precise age for the fossil meteorites, explains Anders Lindskog from the Geological Department, Lund University, who is the lead-author on the study. He was the one who recovered the zircons when studying the rock layers containing the fossil meteorites and subsequently sent them to the Natural History Museum of Denmark, which has the facilities and experience to conduct high-precision dating of rocks.

Calculating the age of the zircons

In Copenhagen, the zircons were handed over to postdoc Mafalda Costa from Centre for Star and planet Formation (StarPlan) at the Natural History Museum of Denmark, who processed and analyzed the minerals in the radiogenic isotope laboratory at the Geological Museum.

Mafalda Costa explains:

Zircons occur in a wide variety of rocks, including in ash layers associated with volcanic eruptions. The determination of the age of these crystals is based on the natural radioactivity of uranium, which is incorporated in the mineral upon crystallization, and that from that moment until today, at a known rate, has been spontaneously decaying to lead. We measure the amount of uranium and lead present in the zircons and from that it is possible to calculate an age that pinpoints the time when they erupted on the surface. In this case, on the same surface that also contained meteorites originating from the asteroid break-up. In this way, we could precisely define the age of the fossil meteorites, explains Mafalda Costa, and adds:

From other isotope analyses of minerals found in the fossil meteorites it had been previously estimated how much time the meteorites spent in space before reaching Earth. Hitherto it was not precisely known when this happened. With our new zircon age, we can determine that the rise in biodiversity occurred ~2.5 million years prior to the asteroid break-up took place.

This new study, which has just been published in the renowned journal Nature Communications, therefore demonstrates that there is no link between the Ordovician rise in biodiversity and the asteroid break-up -- thus, some other driver must have facilitated the Ordovician radiation.
-end-
Contact

Christian Mac Ørum Rasmussen
Adjunkt vStatens Naturhistoriske Museum
Københavns Universitet
Mail: christian@snm.ku.dk
Mobil: 21-74-16-70

Maria Mafalda Canas Portela Costa
Postdoc
Center for Stjerne- og Planetdannelse
Statens Naturhistoriske Museum
Københavns Universitet
Mail: mafalda.costa@snm.ku.dk
Mobil: 52-71-66-98

Anders Lindskog
Lunds Universitet
Department of Geology
Mail: anders.lindskog@geol.lu.se
Telefon: +46-46-222-08-89

Faculty of Science - University of Copenhagen

Related Biodiversity Articles:

Mapping global biodiversity change
A new study, published in Science, which focuses on mapping biodiversity change in marine and land ecosystems shows that loss of biodiversity is most prevalent in the tropic, with changes in marine ecosystems outpacing those on land.
Bee biodiversity barometer on Fiji
The biodiversity buzz is alive and well in Fiji, but climate change, noxious weeds and multiple human activities are making possible extinction a counter buzzword.
What if we paid countries to protect biodiversity?
Researchers from Sweden, Germany, Brazil and the USA have developed a financial mechanism to support the protection of the world's natural heritage.
Grassland biodiversity is blowing in the wind
Temperate grasslands are the most endangered but least protected ecosystems on Earth.
The loss of biodiversity comes at a price
A University of Cordoba research team ran the numbers on the impact of forest fires on emblematic species using the fires in Spain's DoƱana National Park and Segura mountains in 2017 as examples
Biodiversity and carbon: perfect together
Biodiversity conservation is often considered to be a co-benefit of protecting carbon sinks such as intact forests to help mitigate climate change.
The last chance for Madagascar's biodiversity
A group of scientists from Madagascar, UK, Australia, USA and Finland have recommended actions the government of Madagascar's recently elected president, Andry Rajoelina should take to turn around the precipitous decline of biodiversity and help put Madagascar on a trajectory towards sustainable growth.
Biodiversity draws the ecotourism crowd
Nature -- if you support it, ecotourists will come. Managed wisely, both can win.
Biodiversity for the birds
Can't a bird get some biodiversity around here? The landscaping choices homeowners make can lead to reduced bird populations, thanks to the elimination of native plants and the accidental creation of food deserts.
Biodiversity can also destabilize ecosystems
According to the prevailing opinion, species-rich ecosystems are more stable against environmental disruptions such as drought, hot spells or pesticides.
More Biodiversity News and Biodiversity Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.