Think the asteroid that wiped out the dinosaurs was bad? Think again. Two newly published studies on tiny geological features called “spherules” suggest that impact events of this magnitude and greater have actually been commonplace throughout Earth’s early history.
In fact, these brand new findings indicate that massive, “dinosaur-killer” asteroids were likely part of a larger barrage of extraterrestrial impact events that endured for billions of years longer than previously believed. Earth’s history just got a lot more violent.
Both studies, published together in this week’s issue of Nature, are largely concerned with tiny, millimeter-wide droplets known as spherules, which researchers have found embedded in layers of rock all over the world. You can think of spherules as the fingerprints left behind by enormous impact events.
When a massive asteroid rams into Earth, the sheer force of the collision is powerful enough to send plumes of molten and vaporized rock careening out into space. Jettisoned material that fails to escape Earth’s gravitational pull cools, condenses and solidifies into spherules. When they return to Earth, these tiny particles coat the planet’s surface in a thin layer known as a spherule bed. Billions of years later, researchers can examine these layers and estimate when a particular spherule bed formed. The layer of spherules found in the rock sample featured here, for example, dates to about 2.63 billion years ago.
