A physical model explaining the origin of the diamond shape of the Bennu and Ryugu asteroids

Cairo – Samia Sayed – A team of scientists used simple concepts from granular physics to explain the bizarre diamond shapes of two near-Earth asteroids, Bennu and Ryugu. early days of the solar system and the formation of the planets.

According to RT, most asteroids are trapped in the Asteroid Belt, a region between Jupiter and Mars. This distance from Earth makes it difficult to study, but sometimes an asteroid escapes and approaches Earth, allowing it to be photographed up close using an unmanned spacecraft.

This is what happened to the two “diamond” asteroids, Bennu and Ryugu, which are classified as rubble heap asteroids, meaning they are made up of many small pieces of rock material that are loosely linked. by gravity. And basically, it’s just grains that interact with each other, like the sand on our beaches.

Dr Taban Sabwala, lead author of the Granular Matter article and researcher at the Fluid Mechanics Unit at the Okinawa Institute of Graduate University of Science and Technology (OIST), explained, “Previous models attributed these diamond shapes to forces generated by rotation. , which drove the material from the poles to the equator, but when asteroids were simulated using these models, the shape was flattened or asymmetrical instead of diamond.

Until now, its distinctive diamond shape, with the highest poles and an equator, has been the subject of debate among astronomers. According to a simple granular physics model, the scientists observed that the two celestial bodies consist of a mass of debris bound together by a weak gravitational force and that they rotate at high speed on their axis.

Granular physicists can predict the shape of the aggregate based on the different forces affecting the particles, and Dr Sabwala, along with Prof. Benaki Chakraborty and Prof. Troy Scheinbrot of Rutgers University, modeled the evolutionary process of Benno and Ryugu. , using analytical expressions and debris. cumulation simulation.

In this way, they noticed that the centrifugal forces coming from the rotation of the celestial bodies are weaker in the regions near the poles, which leads to the rise of the matter which accumulates there.

Moreover, their calculations indicate that Beno and Ryugu acquired this shape early in their development, unlike previous assumptions which gave them the initial spherical shape which would later deform.

They concluded that the models used so far lacked irregular particles, which are a key component in forming the shape of the asteroid.