A tiny dot has just become two. Europe’s Hera spacecraft, which is on its way to examine the aftermath of NASA’s 2022 asteroid-deflection test, has for the first time imaged the asteroid Dimorphos as a separate object from its larger companion, Didymos. The European Space Agency (ESA) announced the milestone on October 27, and Space.com wrote up the images on November 3.
What the image shows
Hera captured the image on October 18 with its monochromatic Asteroid Framing Camera, from a distance of about 1,280 kilometers (795 miles). The pair of asteroids is currently about 197 million kilometers (122 million miles) from Earth.
“With this image the smaller Dimorphos asteroid becomes visible for the first time,” ESA project scientist Michael Kueppers said. “Before this acquisition the spacecraft was still resolving the Didymos system as a single dot.” He added that Dimorphos is made up of only around one pixel in the image, but is clearly separated from its parent body.
Why this asteroid matters
In September 2022, NASA’s DART spacecraft deliberately crashed into Dimorphos at a speed of 6.1 kilometers per second. ESA says the collision sent a plume of debris across 10,000 kilometers of space and shortened the asteroid’s orbit by around 33 minutes. Dimorphos became the first object in the solar system to have its orbit measurably shifted by human action.
That was a test of a planetary defense idea called kinetic impact: hitting a threatening asteroid hard enough to nudge it off course. The test worked, but ESA says key questions remain. Did the impact leave a crater, or reshape the asteroid entirely? What is Dimorphos made of? And which properties explain a deflection that was much greater than impact simulations predicted?
How big are these rocks?
ESA offers some helpful comparisons. Dimorphos is 151 meters across, about the size of the Great Pyramid of Giza. Didymos is 780 meters across, a little smaller than the Burj Khalifa in Dubai, the tallest building in the world. The two orbit an average of 1.15 kilometers apart, and Dimorphos circles its parent at about 18 centimeters per second.
How Hera got here
The image followed two thruster firings, a week apart earlier in October, that slowed Hera to just 20 meters per second relative to the asteroids. That slow speed lets the spacecraft approach gradually. Space.com notes that Hera launched on a SpaceX Falcon 9 in October 2024 and carries 12 payloads, plus a pair of small CubeSats for a closer look.
What happens next
Hera is not just a camera in the sky. ESA says it will perform a close-up “crash site investigation” over the coming months, using multiple instruments and deploying two shoebox-sized CubeSats for an even closer survey, eventually progressing to landing.
The most exciting date is close. ESA mission manager Ian Carnelli said: “We will unveil the first detailed images of Dimorphos … on 25 November.”
Quick facts
- Mission: Hera, ESA’s first planetary defense mission.
- Targets: the binary asteroid system Didymos and Dimorphos.
- Image date: October 18, 2026, from 1,280 km away.
- Next milestone: first detailed images of Dimorphos on November 25.
Why it matters for the rest of us
A mission to a distant asteroid might sound remote, but the goal is practical. If an asteroid is ever found on a path toward Earth, scientists want to know exactly how well a spacecraft impact can push it aside. Hera’s survey will help turn a one-time experiment into a technique that engineers can reliably plan around, by measuring the asteroid’s mass, structure and the shape of the impact site.
The bottom line
For now, Dimorphos is just one pixel. In three weeks, ESA says, it will become a place with a shape, a surface and a scar from a human-made impact. That is a good reason to mark November 25 on your calendar.
*Sources: ESA and Space.com, as linked above. Distances and dates are as reported by ESA.*
Image: Double asteroid didymos system by NASA/Johns Hopkins APL via Wikimedia Commons, Public Domain Mark 1.0
