NASA successfully demonstrated that it would be feasible, if required, to alter the course of a celestial object traveling towards Earth and maybe prevent a catastrophic impact when it sent its “DART” spacecraft to collide with an asteroid in 2022.

But as it turns out, the deliberate collision also altered the Dimorphos asteroid’s shape, according to scientists’ findings on Tuesday.

Dimorphos was a “roughly symmetrical oblate spheroid,” according to NASA, prior to the impact. Stated otherwise, “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?

Steve Chesley, a senior research scientist at NASA’s Jet Propulsion Laboratory (JPL) in California and author of the published study, believes that the asteroid’s makeup is to blame for 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”.

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.

“By measuring the pre- and post-impact orbit of Dimorphos, we were able to deduce the change in the shape,” explained JPL navigation engineer and study lead author Shantanu Naidu, adding: “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,” Chesley said.

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