A piece of clay attached to a wand deforms in the rushing water as part of an experiment.
Credit: NYU's Applied Mathematics Laboratory [1
Most meteorites on Earth are just randomly shaped blobs. But a surprising number of them, about 25%, are cone-shaped when you put all the pieces together again. Scientists call these conical space stones "oriented meteorites". And now, thanks to two experiments published online today (July 22) in the Journal Proceedings of the National Academy of Sciences (PNAS), why: The atmosphere cuts the rocks into more aerodynamic shapes as they fall to earth.
"These experiments tell an origin story for oriented meteorites," said Leif Ristroph, a mathematical physicist at the New York University (NYU) who led the study, in a statement. "The very aerodynamic forces that melt and transform 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 is difficult to replicate meteoroids precisely on their way to the surface of our planet. The space rocks enter the atmosphere at a high velocity and produce violent, sudden friction that heats, melts and deforms the objects as they tumble free. These conditions did not exist in the NYU lab where the study was conducted, but the researchers approached these factors by using softer materials and water and breaking the experiment into parts.
First, the researchers put balls of soft clay into the center of water streams, a rough approach to a heavy rock that hits an atmosphere. The sound, the scientists found, tended to deform and erode.
But this experiment alone would not explain much. The soft sound was not allowed to move in the water – a very different situation than a stone that stumbles freely through the upper atmosphere and somehow oriented.
For the second step, researchers threw different types of cones into the water to see how they fell. It turns out that cones that are too narrow or too fat tend to fall, as would stones with another shape. But there were "Goldilocks" cones between these two extremes that moved until their points were directed like an arrow in their direction of travel, and then slid smoothly through the water.
These two experiments seem to show this together when When certain conditions are met, space rocks under the extreme friction of an atmospheric inlet develop conical shapes. And sometimes these conical parts help to stabilize these tumbling stones and show a steady direction when falling. This stability, in turn, will always make it more conical. When these rocks hit the ground, meteorite hunters encounter the remnants of "oriented" conical space rock.
Originally published on Live Science .