In September 2022, NASA’s Double Asteroid Redirection Test (DART) mission jogged the scientific community. The mission’s success wasn’t just about proving humanity’s ability to nudge a celestial object – it turns out the collision with the DART spacecraft also dramatically reshaped the target asteroid, Dimorphos.
Before the impact, Dimorphos resembled a “squashed ball,” as scientists described it – an oblate spheroid, wider at the equator than at the poles. But new observations paint a different picture. The impact from the DART spacecraft, meticulously documented by a companion observation satellite, DRACO, has transformed Dimorphos into a more oblong shape, likened to a “watermelon” by Shantanu Naidu, a navigation engineer at NASA’s Jet Propulsion Laboratory leading the study. Technically, this new form is called a “triaxial ellipsoid.”
This shape change isn’t purely aesthetic. It provides valuable clues about the composition of Dimorphos. The fact that the impact caused such a significant deformation suggests a loose, rubble-pile structure for the asteroid. This reinforces the effectiveness of the kinetic impact technique employed by DART, where a high-speed collision transfers momentum to the asteroid, altering its trajectory.
The DART mission aimed to demonstrate the feasibility of deflecting a potentially hazardous asteroid on a collision course with Earth. Dimorphos’s successful 33-minute orbital nudge—exceeding initial expectations—validated this approach. However, the unexpected shape change adds another layer to the mission’s success.
“When DART made an impact, things got very interesting,” said Naidu. “Not only did the impact alter Dimorphos’ orbit, but how it deformed tells us much about its internal structure. This information will be crucial for future missions aimed at deflecting asteroids.”
Understanding the composition of near-Earth objects (NEOs) is vital for planning future deflection missions. A solid, monolithic asteroid might require a different strategy than a loose rubble pile like Dimorphos. The DART data will lead to more targeted techniques in future planetary defense endeavors.
The DART mission and its impact on Dimorphos have opened a new chapter in our understanding of asteroids and planetary defense. The mission’s success signifies a technological leap and highlights the importance of international collaboration in safeguarding our planet from potential cosmic threats. The reshaped Dimorphos serves as a testament to humanity’s growing capability to influence the fate of celestial objects, and the knowledge gained from this mission will be a stepping stone for future endeavors to ensure a safe future in our cosmic neighborhood.