Hubble image of asteroid Dimorphos. Credit: NASA, ESA, David Jewitt (UCLA), Image Processing: Alyssa Pagan (STScI).

Check out what Hubble saw as it spied on asteroid Dimorphos

Astronomers have been closely monitoring the aftermath of this cosmic encounter with the aid of the Hubble Space Telescope.


Remember the asteroid NASA smashed a spacecraft into? Well, it turns out it is giving us a lot of information about how these objects behave. Hubble is helping us better understand the impact, and speaking of Hubble, check out what the space telescope saw as it spied on Dimorphos post-collision.

The potential threat that stray asteroids pose to our planet is no novelty. Recalling the extinction of dinosaurs, the result of a massive asteroid impact some 65 million years ago, scientists today aim to veer humanity away from a similar disaster by exploring techniques to redirect any approaching Earth-bound asteroids.

However, the process isn’t as easy as depicted in sci-fi films like Deep Impact. First off, scientists need to understand the composition of these celestial bodies: are they merely an amalgamation of loosely bound rocks, or do they present a more solid form? These are key details that will influence our strategies for asteroid deflection.

What Hubble Saw as it Spied on Asteroid Dimorphos

As an initial measure, NASA launched an experiment to probe an asteroid’s reaction to a collision. On September 26, 2022, the DART (Double Asteroid Redirection Test) spacecraft made an impactful rendezvous with asteroid Dimorphos. Astronomers have been closely monitoring the aftermath of this cosmic encounter with the aid of the Hubble Space Telescope.

An unexpected observation followed this space experiment: several dozen boulders were dislodged from the asteroid following the collision. In Hubble’s images, these fragments resemble a slow-moving swarm of bees drifting away from Dimorphos. This indicates that redirecting an asteroid could potentially lead to a barrage of smaller, yet still threatening, boulders spiraling towards Earth.


Asteroid Debris: The Unexpected Aftermath of Collision

The DART spacecraft’s deliberate collision caused Dimorphos to deviate slightly in its orbit around the larger asteroid, Didymos. Hubble’s remarkable detection capabilities have revealed a cluster of boulders, presumably dislodged from Dimorphos due to the forceful impact of the half-ton DART spacecraft. These ejected boulders, ranging from three to 22 feet in diameter, are drifting away from Dimorphos at a pace marginally faster than a giant tortoise’s walk.

“These are much more impressive findings than anticipated,” commented David Jewitt, a planetary scientist from the University of California at Los Angeles, “The number, sizes, and shapes of these boulders are in line with what we expected from the impact on Dimorphos.”

A New Chapter in Asteroid Study

Jewitt further explains that this provides new insights into what occurs when an asteroid is hit, including the ejection of material up to the largest sizes. This sets the stage for studying the DART experiment’s aftermath using the European Space Agency’s forthcoming Hera spacecraft, due to arrive at the binary asteroid in late 2026.

“The boulder cloud will still be expanding by the time Hera arrives,” Jewitt said. The boulders appear to be pre-existing debris on Dimorphos’s surface, rather than fragments resulting from the impact. Jewitt estimates that two percent of the asteroid’s surface boulders were dislodged due to the impact.

Post-Impact Speculations and Future Observations

The ejected boulders also provide clues about the impact crater’s size, believed to be around 160 feet in diameter. The final determination will be made once Hera arrives at the scene. It is speculated that Dimorphos was formed from material ejected by Didymos, making it a “flying rubble pile” loosely bound by gravity.


How the boulders were lifted off the asteroid’s surface is still unclear. They could be part of an ejecta plume or a result of a seismic wave from the impact that shook loose the surface rubble. “By continuing to observe these boulders with Hubble, we might be able to determine their precise trajectories and discern the directions from which they were ejected,” Jewitt added.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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