We knew that the DART mission changed the trajectory of Dimorphos. What we didn’t know is that it also changed its shape.

In late September 2022, the DART mission (Double Asteroid Redirection Test) made history, curiously, by crashing into an asteroid. The milestone was not the impact itself but its ability to slightly deflect the trajectory of an asteroid, Dimorphos.

The expected and the unexpected. A new study on the effects of the DART impact on the asteroid Dimorphos They have revealed new details As expected and as the first analyses had revealed, DART managed to deflect the orbital trajectory of the space rock. However, its impact also caused it to become noticeably deformed.

The asteroid, the team explains, initially had an oblate shape, that is, flattened at the poles, like the Earth, “the shape of a hamburger,” they say. After the impact, the asteroid became more prolate, elongated at the poles, like a rugby ball.

“For the most part, our pre-impact predictions about how DART would change the way Didymos and its moon [Dimorphos] move in space were correct,” explained in a press release Derek Richardson, who leads the analysis of the probe’s effects. “But there are some unexpected discoveries that help provide a better picture of how asteroids and other small bodies form and evolve over time.”

Stumbling around. According to the new study, the impact would have caused Dimorfos to move from a state of equilibrium with its parent asteroid Didymos similar to that between our Moon and Earth. In other words, Dimorfos always had the same face towards Didymos, at least until DART arrived.

The system is now out of alignment, Richardson says. This means it can wobble, changing orientation, or even end up “tumbling,” rotating in chaotic and unpredictable ways.

Asteroid formation. The new study may also provide clues about asteroid formation. The impact released small rocks into the orbit of the asteroid system, the team explains. These contributed to altering the orbital motion in the system, but these changes in the gravitational balance do not seem to have altered the shape of Didymos.

This implies, the team adds, that the system’s parent asteroid was rigid and firm enough to maintain its shape after the formation of its moon Dimorfos. Details of the work were published in an article in the magazine Planetary Science Journal.

Hera’s turn. The scientific community is waiting The arrival of Herathe European Space Agency (ESA) mission to monitor the system and collect new data in situIf all goes according to plan, Hera will begin a journey in October that will take it to reach the double asteroid towards the end of 2026.

The data collected by Hera will allow for an even more thorough analysis of the impact of the DART mission. This in turn will provide us with key clues that will allow us to plan missions to protect our planet from asteroid impacts.

Hera may also tell us when this system will return to the equilibrium from which the DART mission brought it. The team is even speculating about the possibility of a mission to reach the surface of the asteroid. It will take a long time before planning such a mission can even begin.

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Image | NASA/Johns Hopkins APL/Steve Gribben