DART Mission Didn’t Just ‘Redirect’ an Asteroid, But Also Reshaped It

Schematic of the DART mission shows the impact on the moonlet of asteroid (65803) Didymos. Post-impact observations from Earth-based optical telescopes and planetary radar would, in turn, measure the change in the moonlet’s orbit about the parent body.

Representational image


Deflecting an asteroid by knocking off course with a rocket might sound like something out of a grade schooler’s creative writing homework, but NASA really did that. NASA’s DART mission, short for Double Asteroid Redirection Test, was a historic experiment launched in September 2022. It successfully slammed a spacecraft into a small asteroid named Dimorphos, not to destroy it, but to nudge it slightly — demonstrating our ability to deflect potentially dangerous asteroids in the future.

Now, new research suggests the DART mission may have significantly changed the shape of the tiny asteroid Dimorphos, rather than just nudging it off course. This not only offers clues about Dimorphos’ formation, but also means the upcoming mission to study it won’t find an impact crater, but a potentially “reformed” asteroid.

As humanity’s first attempt at such a feat, DART left scientists unsure about long-term effects and what it might reveal about the asteroid itself. Enter planetary scientist Sabina Raducan and her team who, instead of observing Dimorphos directly, ran simulations. They virtually recreated Dimorphos, the DART impact, and analyzed the observed effects, like momentum transfer, ejected material (ejecta cone), and the unknown: Dimorphos’ composition and density.

Asteroids come in different “builds.” Some are dense, like leftover planetary chunks. Others are “rubble piles,” loosely bound collections of dust and rock. Both Didymos and Dimorphos belong to the latter category.

Interestingly, the simulations suggest DART didn’t leave a crater. Instead, the impact caused a “global resurfacing” of the asteroid, hinting at an extremely weak, “rubble pile-ier” Dimorphos than previously thought. Its strength is estimated to be less than a few pascals, comparable to asteroids Ryugu and Bennu, previously explored by spacecraft.


The simulations also suggest Dimorphos is quite low-density, around 2.4 grams per cubic centimeter – denser than Ryugu and Bennu, but still much less than Earth. This, combined with the ejected boulder density, further supports the “rubble pile baby” theory. The model proposes Dimorphos formed from debris shed by Didymos due to its spin. Over time, this debris clumped together into the loose, reshaped asteroid we “smacked” with DART.

The European Space Agency’s upcoming Hera mission will be crucial in verifying these findings. If Hera’s observations align with the simulations, we’ll gain valuable insights into not only Dimorphos’ evolution but also asteroid formation, binary systems, and future deflection strategies.

This research doesn’t just tell us about Dimorphos; it highlights the potential for similar asteroids to be easily reshaped. Overall, it provides valuable knowledge for future asteroid exploration and deflection efforts, reminding us that space exploration is full of unexpected discoveries, even from a well-planned “cosmic nudge.”


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