1709005166 Dimorphos a real pile of rubble

Dimorphos, a real pile of rubble

The asteroid Dimorphos, the subject of a new experiment to divert its trajectory, has everything from a pile of debris from the larger asteroid Didymos around which it orbits, shows a study published in the journal Nature Astronomy (New Window).

Dimorphos was hit by NASA's DART spacecraft in September 2022 to test the ability to divert an asteroid that could hit Earth from its trajectory.

Two light spots, one small and one large, on a dark background.

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The asteroid Didymos (top left) and its satellite Dimorphos, about 2.5 minutes before DART impacted the latter. The image was taken by the DRACO imager at a distance of 920 kilometers.

Photo: NASA/Johns Hopkins

The success of the mission, which took place around 11 million kilometers from Earth, could only be measured by the impact of the impact on Dimorphos' orbit around Didymos.

In this strange pair, the first star, with a diameter of about 160 meters, initially orbited the second, with a diameter of 800 meters, in almost 12 hours. A time after impact reduced by more than half an hour. The detail was captured in images by an Italian microsatellite accompanying the DART mission and tracked from Earth using telescopes.

According to the international team led by Sabina Raducan, a specialist in small celestial bodies at the University of Bern, these data indicate that Dimorphos is a pile of rubble, their study summarizes.

According to the simulations, the only solutions we find assume that Dimorphos was originally a very fragile star that offered very little resistance to the impact of DART and its 610 kg weight, explains study co-author Patrick Michel, astrophysicist on the Côte d'Azur. Azure Observatory.

Such fragility that the impact would not only have created a crater about ten meters in diameter, but would actually have led to a complete deformation of the star's body, adds this co-leader of the DART team.

Pebble field

Use of the condition is essential while waiting for the European Space Agency's (ESA) HERA probe, scheduled to reach Dimorphos in 2026, to study the asteroid with much larger resources.

Dimorphos would consist of a heterogeneous silica-based collection, but not the kind of sand field like in Saint-Tropez, but a pebble field like on the Promenade des Anglais in Nice, with stones everywhere, smiles Patrick Michel. Rather small rocks, as less than 40% are more than 2.5 meters long, according to the simulations supported by the last images taken by DART before the ship crashed.

And above all, the structure of the star, which we can study with a low-frequency radar from HERA, would be characterized by great porosity, which explains its fragility.

Which speaks of a birth and growth based on debris ejected by his big brother Didymos, who spins like a top, of which he is a little in shape elsewhere. With sufficient speed to eject some of its material through centrifugal action, which agglomerates into dimorphos.

This in itself would be good news for Patrick Michel, who confirms that a silicate asteroid like Dimorphos exhibits roughly the same behavior as the more common carbonaceous asteroids like Bennu or Ryugu, that is, very little drag.

So we would already know who we are dealing with if, in the distant future, it were necessary to distract someone in order to save the Earth. A great advance, because these objects exhibit behavior that contradicts our intuition since they are in a completely different environment than on Earth, emphasizes the expert.

In 2029, the asteroid Apophis will pass close to Earth at a distance of about 32,000 kilometers, providing a natural laboratory for studying these stars, he expects.

A mission is being prepared to study the behavior of Apophis during its passage without having to touch it since it will be visible from the ground.