The asteroid Demorphos, which is undergoing a unique experiment to divert its path, looks like a pile of debris coming from Didymos, a larger asteroid orbiting it, according to a study whose results were published on Monday.
A collision with the asteroid Demorphos was conducted in September 2022 by NASA’s DART spacecraft, to test the ability to deflect an asteroid that might strike Earth off course.
The success of the mission, which took place about 11 million kilometers from Earth, can only be measured by the impact result on the Demorphos orbit around Didymos.
In this strange duo, the first star, approximately 160 meters in diameter, orbited around the second star, 800 meters in diameter, in approximately 12 hours. The time was shortened by more than half an hour after the collision.
The details were captured in images by a small Italian satellite that was accompanying the DART mission, and were also followed from Earth with telescopes.
According to the international team led by Sabina Raducan, a specialist in small celestial objects at the University of Bern, these data “suggest that Dimorphos is a pile of debris,” according to the results of their study published in the journal “Nature Astronomy.”
Patrick Michel, an astrophysicist at the French Observatory of the Côte d’Azur, co-author of the study, explained to Agence France-Presse that “according to the simulations, the only solutions we found assume that in the beginning, Dimorphos was an extremely fragile ‘object’ and showed little resistance” to the vehicle’s collision. “Dart” weighs 610 kilograms.
The co-responsible of the “DART” team added that this fragility was so great that “the impact, instead of creating a crater with a diameter of only about ten meters, may actually lead to complete deformation of the body” of the asteroid.
Gravel field
These conclusions remain incomplete pending the European Space Agency’s HERA probe, which is scheduled to arrive at Dimorphos in 2026, to examine the asteroid with more precise means.
It is believed that Dimorphos may consist of a heterogeneous aggregate based on silica (silicon dioxide), but not from a “sand field” as in Saint-Tropez, but rather more like a gravel field as in the Promenade des Anglais in Nice (south of France). With rocks everywhere,” said Patrick Michel. These rocks are rather small, as less than 40% of them are more than 2.5 metres, according to simulations supported by the latest images taken by the DART spacecraft before it crashed.
Above all, the structure of the asteroid, which the Hera probe’s low-frequency radar will be able to examine, is probably very porous, which explains its fragility.
This supports the hypothesis of the birth and growth of the space body, based on the debris thrown out by the “big brother” Didymus, which rotates on itself like the toy bulbul (a spinning top), which it somewhat resembles. This happens quickly enough to expel a portion of its material through the centrifugal effect, which agglomerates to form dimorphose.
This in itself constitutes “good news” for Patrick Michel, as he confirms that an asteroid full of silica like Dimorphos has almost the same behavior as the more common carbon asteroids, such as Bennu or Ryugu, “that is, very little resistance.”
Therefore, we already know what to expect, and if in the distant future it will be necessary to divert an asteroid to save Earth from the risk of colliding with it. The expert confirms that this is a major achievement because these objects “have behavior that challenges our intuition, because their environment is completely different from the Earth’s environment.”
In 2029, the asteroid Apophis will pass near Earth, about 32,000 kilometers away, providing a “natural laboratory” for studying these stars, according to Michel.
A mission is currently being prepared to study the behavior of Apophis during its passage without the need to touch it because it will be visible from Earth.
