A new study reveals what makes a meteorite a planet-wide killer, particularly those associated with mass extinction events like the space rock that killed off the dinosaurs. And surprisingly, the size of the meteorite is not as important as the Earth material it slams into.
BACKGROUND: METEORITES AND MASS EXTINCTION
Earth is under constant bombardment from meteors of all sizes. Some of the largest and most potent have been identified by researchers as triggers for mass extinctions of species across the entire globe. For the most part, the physical size of these impacting meteors has been associated with their deadly power, and for good reason; the larger the rock, the more kinetic energy it releases upon impact. However, not every large impact has led to mass extinction events, including a handful of recorded impacts that were larger than the famed dinosaur killer K/Pg Chixulclub.
This imbalance motivated a team of researchers led by scientists at the University of Liverpool to try to understand what makes one meteorite less potent than another, particularly when it comes to the extermination of life. And what they found deems to indicate that the material being slammed into, and therefore released into the atmosphere, is likely the clinching component for extinction-level potency.
ANALYSIS: IMPACT COMPOSITION AND METEORITE DESTRUCTIVENESS
“For decades scientists have puzzled over why some meteorites cause mass extinctions, and others, even really big ones, don’t,” said study co-author Dr. Chris Stevenson, a sedimentologist from the University’s school of Earth, Ocean and Ecological Sciences in a press release announcing the team’s results. “Many kill mechanisms have been proposed, such as large volcanic eruptions, but just like meteorites, these don’t always correlate with mass extinctions.”
To try and solve this mystery, the research team looked at 44 massive impacts spread across Earth’s last 600 million years. Only, instead of focusing purely on size, the team zeroed in on the earthly material ejected into the atmosphere as a result of these massive impacts.
Published in the Journal of the Geological Society of London, their findings “reveal that meteorites that hit rocks rich in potassium feldspar (a common and rather benign mineral) always correspond with a mass extinction episode, irrespective of size.”
This result, they say, is probably because potassium feldspar, which is non-toxic, is a “powerful ice-nucleating mineral aerosol that strongly affects cloud dynamics, which makes them let through more solar radiation.”
That increase in solar radiation hitting Earth resulted in massive planetary warming, as well as a planet-wide increased sensitivity to volcanic eruptions and other greenhouse gas emitting events that also heated up the overall environment. The deadly combination created a perfect storm of global warming, which seems to have been the main cause of other mass extinction events as well.
“It’s surprising when we put together the data: life carried on as normal during the 4th largest impact with a crater diameter of ~48 km, whereas an impact half the size was associated with a mass extinction only 5 million years ago,” said Stevenson. “Using this new method for assessing the mineral content of the meteorite ejecta blankets, we show that every time a meteorite, big or small, hits rocks rich in potassium feldspar it correlates with a mass extinction event.”
OUTLOOK: WHEN IS THE NEXT KILLER METEORITE IMPACT EXPECTED?
There is currently no sure-fire mechanism to predict when or where the next planet-killing meteorite impact will occur. In fact, such a potentially devastating meteor recently flew by Earth and we didn’t even know it was coming until it was too late.
NASA recently released a new app that allows users to track the tens of thousands of near Earth objects (NEOs) that may include the next extinction level impactor. However, the research team involved in the new study thinks their study results can help those looking at the past as well as the future, while simultaneously highlighting the potential damaging effects to the planet caused by everyday human activity.
“This opens up a whole new avenue of research: what exactly kills off life during these episodes, and how long do the potassium feldspar effects last?” said Stevenson. “Until now, only meteorites have changed the aerosol regime of the climate. However, present day human activities represent a similar mechanism with increasing emissions of mineral aerosols into the atmosphere.”
Follow and connect with author Christopher Plain on Twitter: @plain_fiction