Asteroid Dimorphos’ Form Was Also Altered By NASA Missions

NASA successfully demonstrated that, if necessary, it would be feasible to adjust the course of a celestial object headed towards Earth and potentially escape a catastrophic catastrophe when it launched its “DART” spacecraft to collide into an asteroid in 2022.

Scientists revealed on Tuesday that the deliberate impact not only altered the Dimorphos asteroid’s trajectory but also altered its shape.

Dimorphos was characterized by NASA as a “roughly symmetrical oblate spheroid” prior to the collision. Alternatively put, “like a squashed ball that is wider than it is tall.”

After the collision, it was now described as more akin to a “triaxial ellipsoid” or a “oblong watermelon.”

How May the Form of An Asteroid Change?

How may the form of an asteroid change?

Steve Chesley, a co-author of the study published in The Planetary Science Journal and senior research scientist at NASA’s Jet Propulsion Laboratory (JPL) in California, believes that the composition of the asteroid is the explanation behind this.

“The prevailing understanding is that Dimorphos is a loosely packed agglomeration of debris ranging from dust to gravel to boulders,” he said. “Thus, its global strength is quite low, allowing deformation much more easily than for a solid monolithic body.”

About 11 million kilometers (6.8 million miles) from Earth, Dimorphos is actually a moonlet in orbit around Didymos, a “near Earth asteroid”.

Prior to September 26, 2022, at 22,530 kilometers per hour, Dimorphos would collide with the DART (Double Asteroid Redirection Test) probe.

Dimorphos would take 11 hours and 55 minutes to make one orbit around Didymos before crashing into the DART (Double Asteroid Redirection Test) spacecraft on September 26, 2022, at a speed of 22,530 kilometers per hour. That’s now down to thirty-three minutes and fifteen seconds.

Lead author Shantanu Naidu of JPL, a navigation engineer, said, “By measuring the pre- and post-impact orbit of Dimorphos, we were able to deduce the change in the shape,” He added, “The shape change was so dramatic because of its rubble-pile composition.”

How Were The Changes Measured by NASA?

In order to infer what had happened to the asteroid after impact, the researchers said they used three data sources in their computer models: images taken by DART itself as it approached Dimorphos, data from radio waves bouncing off the asteroids, and measurements from ground-based telescopes measuring how sunlight reflected off the surfaces of the two asteroids changed over time.

Chesley said, “We never expected to get this kind of accuracy.”

The Hera mission, scheduled for flight in October by the European Space Agency (ESA), is expected to arrive at the two asteroids in late 2026 and provide an update on the condition. It is not meant to collide with either object.

“We are anxiously awaiting the arrival of ESA’s Hera spacecraft, when we will be able to compare our modeled shape with that obtained from Hera imagery. We will also learn how much the orbit has changed since we last observed it in 2023,”  stated Chesley.

In reality, neither Didymos nor Dimorphos—whether shaped like an egg or a watermelon—were a threat to Earth.

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