Astronomers debunk the mystery of Earth’s “space cones”

Earth is filled with cones that come from space. Fortunately, astronomers have figured out that they aren’t as mysterious as people previously believed – as it turns out, they’re just meteorites that plunged into the Earth’s atmosphere.

Since the Earth began forming around 4.5 billion years ago, it has been peppered by asteroids and meteors alike. The Earth’s geological history has been shaped by impacts from space rocks. While these chunks of rock come in different shapes and sizes, a surprising number of them appear to be cone-shaped.

A vast majority of the meteorites that land on the Earth have irregular shapes. However, a large portion of these meteorites – about 25 percent, in fact – are cone-shaped. Scientists have spent years piecing meteorites back together and found that a lot of them are bullet-shaped. They have since taken to calling these cone-shaped space rocks “oriented meteorites.” (Related: Organic matter found in ancient meteorites may hold clues to understanding the birth of life on Earth.)

The cones are formed through extreme friction

In a study published in the journal Proceedings of the National Academy of Sciences, scientists, after conducting a series of experiments, were able to figure out the reason for the rocks’ peculiar shape: their form is a direct result of their travel through the Earth’s atmosphere.

“By showing how the shape of an object affects its ability to fly straight, our study sheds some light on this long-standing mystery about why so many meteorites that arrive on Earth are cone-shaped,” the researchers stated.

In their study, the researchers replicated the meteorites using clay objects which were attached to a rod. These were then held in water with a current. After a while, the current eventually molded the objects into cones that had the same angularity as the oriented meteorites.

However, the researchers understood that this experiment wasn’t enough, and so they conducted additional tests in which they examined how cones with different shapes fell through the water.

As detailed in their study, the researchers discovered that the shape of the oriented meteorites was just right because they were neither too narrow nor too broad. According to the researchers, the cones that were too narrow flipped over, while those that were too broad fluttered. However, the clay that had the shape of the oriented meteorites flew straight.

Together, these two experiments showed that when certain conditions are present, meteorites will form conical shapes due to the extreme friction that comes with atmospheric entry. A lot of the time, this conical shape will help the meteorites stabilize as they rapidly descend onto the Earth. This stability, in turn, helps to turn them into even more conical meteorites.

“These experiments tell an origin story for oriented meteorites,” said Leif Ristroph, lead of the study and mathematical physicist for New York University. “The very aerodynamic forces that melt and reshape meteoroids in flight also stabilize its posture so that a cone shape can be carved and ultimately arrive on Earth.”

“This is another interesting message we’re learning from meteorites, which are scientifically important as ‘alien visitors’ to Earth whose composition and structure tell us about the universe.”

Ristroph and his colleagues further conclude that, while the exact origin of oriented meteorites is still unknown, their study should, at the very least, widen people’s appreciation for how certain conditions need to be met for these perfectly-shaped space rocks to land on Earth.

Sources include:

LiveScience.com

UniverseToday.com

EurekAlert.org

PNAS.org