The Hera asteroid probe has observed an enigmatic moon of Mars while conducting a flyby.

The Hera probe has swung around Mars, using the planet’s gravitational pull to fling itself toward its asteroid target. During its brief rendezvous with the Red Planet, Hera caught a glimpse of the less-seen side of Mars’ smaller, tidally-locked moon as it orbited its home planet.

The European Space Agency (ESA) launched its Hera mission on October 7, 2024, to inspect the damage caused by NASA’s DART mission (Double Asteroid Redirection Test) when it smashed into an asteroid to redirect its orbit. Hera is set to reach its asteroid target in 2026, but the space probe got to dust off its science tools for the first time during its Mars flyby on Wednesday.

The spacecraft came as close as 3,106 miles (5,000 kilometers) to Mars, allowing the planet’s gravity to shift Hera’s trajectory toward its target as it cruised through deep space. During its flyby, Hera activated a trio of instruments to image the surface of the Red Planet, as well as its moon Deimos.

“These instruments have been tried out before, during Hera’s departure from Earth, but this is the first time that we have employed them on a small distant moon for which we still lack knowledge – demonstrating their excellent performance in the process!” ESA’s Hera mission scientist Michael Kueppers said in a statement.

Mars has two moons, Phobos and Deimos. Deimos is a tiny little guy, measuring a mere 7.7 miles (12.4 km) across. It may have broken off from Mars in the aftermath of a giant impact, or it’s a small asteroid captured by the planet’s gravity. It completes one orbit around Mars every 30 hours.

Aside from capturing images of the slightly misshapen moon, Hera also performed some joint observations of Deimos with ESA’s Mars Express, which has been in orbit around Mars for more than two decades.

Hera’s target binary asteroid system is much smaller than Deimos. Dimorphos is a 558-foot-wide (170-meter) space rock that orbits its larger 2,625-foot-wide (800-meter) companion, Didymos.

In September 2022, NASA’s 1,340-pound spacecraft smashed into Dimorphos to slightly nudge it as a test of planetary defense. The mission was a success, proving that kinetic impactors can be used to redirect dangerous asteroids should one be headed towards Earth. Datasets gathered by ground-based optical and radio telescopes show that, following the collision, Dimorphos’ orbital period around Didymos shortened from 11 hours and 55 minutes to 11 hours and 23 minutes.

Ground-based observations alone are not enough. That’s where Hera comes in, performing a detailed, post-impact survey from space. The spacecraft is scheduled for a follow-up maneuver in February 2026, followed by a series of thruster firings starting in October 2026 to fine-tune its trajectory to reach the Didymos system in December 2026.

“This has been the Hera team’s first exciting experience of exploration, but not our last,” ESA Hera mission manager Ian Carnelli said in a statement. “In 21 months the spacecraft will reach our target asteroids, and start our crash site investigation of the only object in our Solar System to have had its orbit measurably altered by human action.”