Earth is littered with cones from space, and it’s our planet’s own fault.
Most meteorites found on Earth are just randomly shaped blobs. But a surprisingly high number of them, about 25%, are cone-shaped when you fit all their pieces back together. Scientists call these conical space-stones “oriented meteorites.” And now, thanks to a pair of experiments published online today (July 22) in the journal Proceedings of the National Academy of Sciences (PNAS), we know why: The atmosphere is carving the rocks into more aerodynamic shapes as they fall to Earth.
“These experiments tell an origin story for oriented meteorites,” Leif Ristroph, a New York University (NYU) mathematical physicist who led the study, said in a statement. “The very aerodynamic forces that melt and reshape meteoroids in flight also stabilize [them] so that a cone shape can be carved and ultimately arrive on Earth.” [The 10 Biggest Impact Craters on Earth]
It’s difficult to precisely replicate the environment meteoroids encounter on their way to our planet’s surface. The space rocks slam into the atmosphere at high speeds, generating intense, sudden friction that heats, melts and deforms the objects as they freely tumble. Those conditions didn’t exist in the NYU lab where the study occurred, but the researchers approximated those factors by using softer materials and water, and by breaking the experiment up into parts.