DART spacecraft’s asteroid impact informs new planetary defense strategy

When engineers at a control center in Turin, Italy, sent a faint radio signal into space, they set off a world-first experiment. The message reached NASA’s Double Asteroid Redirection Test spacecraft, better known as DART, more than 5 million miles away. In response, the spacecraft released its traveling partner, a shoebox-sized satellite named LICIACube.

Fifteen days later, DART deliberately collided head-on with Dimorphos, a small moon orbiting a larger asteroid called Didymos. While the spacecraft was destroyed, LICIACube flew past at high speed, capturing the only close-up images of the historic impact. The photos gave scientists the data they needed to calculate how much material was blasted away from the asteroid and how the collision changed its motion.

When DART struck, the tiny spacecraft transferred its energy into Dimorphos. But the real surprise came from what happened next. Scientists analyzing LICIACube’s images reported in The Planetary Science Journal that 35.3 million pounds of rock and dust were ejected. That’s the weight of about 100 fully loaded jumbo jets, hurled into space in seconds.

Though this debris made up less than half a percent of Dimorphos’ total mass, it was still 30,000 times greater than the spacecraft’s weight. The flying rubble acted like a booster rocket, giving Dimorphos an extra push that far exceeded the direct effect of the crash.

“The plume of material released from the asteroid was like a short burst from a rocket engine,” explained Ramin Lolachi of NASA’s Goddard Space Flight Center. The resulting momentum shifted Dimorphos’ orbit around Didymos by 33 minutes, a change that was easily measured from telescopes on Earth.

LICIACube had just one minute to complete its vital task. As it sped by at 15,000 miles per hour, it snapped photos once every three seconds. The closest image was taken from only 53 miles above Dimorphos. The spacecraft’s camera, called LUKE, recorded the event in multiple colors of light. Scientists studied 18 images taken from different angles, watching the debris plume evolve. Early shots showed the cloud shining brightly under direct sunlight. Later images revealed a dimmer glow as sunlight scattered through the dust.

This fading light told researchers that the cloud contained mostly larger particles — many about a millimeter across. Because the innermost region was so thick that no light could pass through, the team relied on models to estimate the unseen mass. Timothy Stubbs, a planetary scientist at NASA Goddard, explained, “We estimated that this hidden material accounted for almost 45% of the plume’s total mass.”

To make sense of the images, researchers compared them with laboratory scattering experiments and computer models. The goal was to understand how particles of different sizes reflect light. By integrating plume brightness across the camera’s field of view, they calculated the amount of material ejected.

Initial estimates suggested at least 19 million pounds were blasted away. But when scientists accounted for the hidden inner plume, the total rose by 77%. The final calculation of 35.3 million pounds is now considered the most accurate measurement. The particle size distribution followed a simple mathematical pattern, known as a power law, where smaller particles are much more common than larger ones. This type of distribution is typical of debris clouds from violent impacts.

The experiment also shed light on Dimorphos itself. The asteroid is what scientists call a “rubble pile” — a loose clump of boulders and dust bound together weakly by gravity. Calculations suggest its strength is less than 50 pascals, softer than compacted snow. That explains why such a small spacecraft could release so much material.

Dave Glenar of the University of Maryland, Baltimore County, noted, “We expect that a lot of near-Earth asteroids have a similar structure to Dimorphos. So, this extra push from the debris plume is critical to consider when building future spacecraft to deflect asteroids from Earth.”

Asteroids pass near Earth all the time, and while most pose no danger, even a small one could cause regional devastation if it hit. The DART mission proved that hitting an asteroid with a spacecraft can shift its orbit. More importantly, the study showed that ejecta — the debris blasted away — can provide a bonus effect, multiplying the deflection.

Future missions will need to consider asteroid type. A rubble pile like Dimorphos reacts differently than a dense, solid rock. Some may eject huge plumes, while others could absorb the impact with less effect. “Every time we interact with an asteroid, we find something that surprises us, so there’s a lot more work to do,” said Stubbs. “But DART is a big step forward for planetary defense.”

The DART experiment did not just change the orbit of a harmless asteroid. It marked the beginning of a practical strategy to protect Earth. LICIACube’s images gave the world its first close-up view of what planetary defense looks like in action: a spacecraft’s sacrifice, a burst of flying rock, and a measurable change in an asteroid’s path.

It is a reminder that even the smallest human technology can influence objects millions of miles away — and perhaps one day, save lives on Earth.

Note: The article above provided above by The Brighter Side of News.

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