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|Don Davis/Southwest Research Institute|
“Looking at the kinds of meteorites that have fallen to Earth in the last 100 million years doesn’t give you a full picture,” said team member Philipp Heck from the Field Museum in Chicago. “It would be like looking outside on a snowy winter day and concluding that every day is snowy, even though it’s not snowy in the summer.”
“We knew almost nothing about the meteorite flux to Earth in geological deep time before this study,” explains team member Birger Schmitz from Lund University in Sweden. “The conventional view is that the Solar System has been very stable over the past 500 million years. So it is quite surprising that the meteorite flux at 467 million years ago was so different from the present.”
“It’s a needle in the haystack problem,” Heck told Sarah Kaplan at The Washington Post. “So we have to take a brute force approach: we burn away the haystack to find the needles.”
“Chrome-spinels, crystals that contain the mineral chromite, remain unchanged even after hundreds of millions of years,” Heck explained. “Since they were unaltered by time, we could use these spinels to see what the original parent body that produced the micrometeorites was made of.”
“Meteorite delivery from the asteroid belt to the Earth is a little like observing landslides started at different times on a mountainside. Today, the rocks reaching the bottom of the mountain might be dominated by a few recent landslides.
“Knowing more about the different kinds of meteorites that have fallen over time gives us a better understanding of how the asteroid belt evolved and how different collisions happened,” Heck concludes.
“Ultimately, we want to study more windows in time, not just the area before and after this collision during the Ordovician period, to deepen our knowledge of how different bodies in Solar System formed and interact with each other.”