NASA’s Asteroid Experiment Changed Space Science Forever

NASA’s DART spacecraft, which had been tracking an asteroid for months, was racing toward it in the last seconds of its mission, returning one picture every second. The final photos showed an egg-shaped group of rocks, followed by a field of boulders, gravel, and dust, and finally nothing. On impact, the camera cut out. One observer described the sound made by scientists watching the feed back on Earth as a mixture of relief and disbelief.

The pictures had already led DART program scientist Tom Statler to his own conclusion. “When I saw Dimorphos come into view and when I saw there was not a single crater on it and there were a lot of what appeared to be loose rocks,” he continued, “I looked at it and I said, ‘This is not going to be 73 seconds.'”

It wasn’t. Dimorphos’s orbit around its larger companion asteroid, Didymos, was to be shortened by at least 73 seconds, according to the mission’s stated objective. A few weeks later, the real outcome was revealed to be 32 minutes.

On September 26, 2022, the 800-pound spacecraft, which was about the size of a vending machine, collided with Dimorphos at a speed of almost 15,000 miles per hour. The collision proved to be far more successful than anyone had publicly predicted. “Let’s all just kind of take a moment to soak this in,” stated Lori Glaze, the head of NASA’s planetary science division, during the subsequent press conference. “Humanity has altered a planetary body’s orbit for the first time ever. For the first time ever.

The majority of people heard that version of the story. The original finding appears to be an understatement in a new study that was published in Science Advances in March 2026. Researchers discovered that the DART impact affected not only Dimorphos’s orbit around Didymos but also the binary system’s overall trajectory around the Sun, affecting both asteroids collectively.

The Didymos-Dimorphos system’s 770-day solar orbital period changed by about 0.15 seconds, and the binary’s speed around the Sun changed by about 11.7 microns per second, or roughly 1.7 inches per hour. The change is negligible in absolute terms. However, the discovery represents the first instance in which a man-made object has significantly changed a celestial body’s orbit around the Sun. Changing the local orbit of a single small asteroid is a different kind of achievement.

The debris was the mechanism that increased DART’s impact beyond what the spacecraft could have generated on its own. Hubble took pictures of a dust tail that stretched 6,000 miles into space after the spacecraft struck, and the debris carried its own momentum away from Dimorphos in the same direction as the impact. This resulted in an enormous plume of rocky material being blasted outward. This is known to scientists as the momentum enhancement factor.

That factor was about two for DART, which means that the impact’s effective push was nearly doubled by the debris ejection. More specifically, the loosely bound rubble-pile structure of Dimorphos allowed massive amounts of material to be expelled in a coherent direction, acting somewhat like exhaust from a thruster, as confirmed by DART’s final images when no craters were visible on its surface.

Years of meticulous observation and the unpaid work of volunteer astronomers across several continents were necessary for the measurement that verified the shift in the solar orbit. Between October 2022 and March 2025, the researchers monitored 22 stellar occultations, which are instances in which the Didymos-Dimorphos system passed exactly in front of a background star, resulting in a brief dimming that could be seen from Earth. Because the asteroid’s shadow track across Earth was brief and narrow, each successful measurement required the coordination of several observation stations, frequently in remote locations, timed precisely. The weather canceled a lot of scheduled observations.

“This work is highly weather dependent and often requires travel to remote regions with no guarantee of success,” stated JPL senior research scientist Steve Chesley, who co-led the new study. All of that work paid off when Didymos’s position and velocity were measured precisely enough to identify a change in solar orbital speed of less than 12 millionths of a meter per second.

Beyond its beauty as a physics demonstration, the result is significant because of its practical implications. Changing an asteroid’s trajectory with respect to Earth is more important for planetary defense than altering its position in relation to other asteroids.

The new study directly demonstrates that a kinetic impactor can change the solar orbit of a binary asteroid system, which is the real factor that determines whether a potentially dangerous object will ever approach Earth. “Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet,” stated Rahil Makadia, the study’s principal investigator from the University of Illinois Urbana-Champaign.

Launched on a SpaceX Falcon 9, the $314 million DART mission concluded with a camera cutout. Launched in 2024, the European Space Agency’s Hera spacecraft is currently on its way to measure Dimorphos’ mass and conduct a thorough survey, completing the remaining data gaps.

NASA is constructing the NEO Surveyor on Earth, a specialized space telescope intended to locate dark asteroids and comets that reflect insufficient light to be readily detected. The link between the impact experiment and the working planetary defense system is longer than it might seem from the outside. However, DART demonstrated the validity of physics. That’s what was actually in doubt, and it’s no longer.