Impact craters are found on almost all rocky bodies in the solar system, from Earth to the icy moons of gas giants. It is characterized by an amazing diversity of shapes and is the result of the collision of comets, asteroids and meteorites with the surface of these celestial bodies. Now, in a new study, a group of researchers has analyzed how some characteristics of these events affect the shape of these holes.
The research was published in the journal Physical review e They investigated how the rotation of granular asteroids, or piles of rubble, affects the shape of impact craters. Contrary to what was thought, it was discovered that as the rotation speed increased during the impact, the crater became wider and deeper, like a bowl.
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Geologists have already noted some of the factors responsible for the different shapes of craters, such as the speed and angle of impact and the size of the object. However, during the new research, scientists focused on verifying parameters that are usually investigated: the speed of rotation during the collision and the gravitational force that binds asteroids to piles of rubble.
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Asteroid's rotation speed
Rotating objects generally carry more energy than non-rotating ones, which can make it appear as if they will create a huge crater when they enter the atmosphere and collide with the Earth's surface. However, when we are talking about objects that are not a monolith, but rather a collection of small rocks held together by gravity, about 70 to 80% of asteroids are, things can be different.
To analyze these factors, the researchers ran simulations, creating digital versions of tangerine-sized asteroids made up of thousands of weevil-sized balls. They were fired onto a granular layer similar to the planet's surface, at different rotational speeds.
The investigation revealed that rapidly rotating granular asteroids can open narrow, deep grooves if they collide with Earth, but only if the gravitational force holding the rocks together is very strong, otherwise they form wide, shallow craters.
This happens because part of the energy carried by the asteroid as it rotates is used to break the bonds holding the rocks together. This leaves these tiny space rocks without enough energy to form deep holes. Some of the craters likely formed in this way are Barringer Crater in Arizona and Flynn Creek Crater in Tennessee, both in the United States.
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