NASA probe could have been swallowed up by the surface of asteroid Bennu
When we think of asteroids, we often think of a large solid rock floating in space. But there are asteroids that are not as compact as rocks, but rather have a crumbling surface. This is the case of the asteroid Bennu which was visited in October 2020 by the space probe OSIRIS-REx. The latter’s mission was to take samples that will be analyzed on Earth.
According to new analyzes carried out by the team in charge of OSIRIS-REx, it has narrowly avoided being engulfed by the asteroid’s surface. Bennu’s surface would indeed look like a swimming pool filled with plastic balls. A person who set foot on it would sink directly.
This new perspective regarding the composition of Bennu’s surface comes from images captured during sample collection.
What the simulations showed
Images taken during the mission showed that the pebbles on the surface had been scattered all around and that one crater with a diameter of 8 m had been created. In April 2021, the space probe returned above the collection location to inspect this craterwhich allowed scientists to analyze images taken before and after the operation. The data corresponding to the acceleration recorded by the probe revealed a very small resistance at the level of the surface.
With the data obtained, the scientists carried out computer simulations to calculate the density and cohesion of materials on the surface of Bennu. The simulations were based on the images obtained by the probe and on the data concerning the acceleration. The team tested various properties until the simulation results agreed with the mission data.
The results revealed that the particles that make up the asteroid’s exterior were loosely piled up. Thus, if the probe had not ignited its thrusters at the right time, it would have sunk through the surface.
A different risk for the Earth
This is a very interesting finding on Bennu’s characteristics. Earlier mission data had indeed suggested that the asteroid was more rugged and eruptive than observations from Earth had shown.
This discovery also has implications for understanding other asteroids and the dangers they can pose.
According to Patrick Michel, one of the scientists in charge of the OSIRIS-REx mission, it is possible that asteroids like Bennu, which are barely held together by gravity and electrostatic forces, break up when they enter the earth’s atmosphere. This could create a different type of danger than that generated by solid asteroids.
For Michel, we are only at the beginning of the understanding of these space objects.