European spacecraft captures rare images of Mars moon Deimos

Mars' moon Deimos silhouetted against the red planet, which appears blue from an infrared image, as captured by ESA’s Hera spacecraft. Photo / AFP

• A European spacecraft captured rare images of Mars moon Deimos during its journey to an asteroid.
• The Hera mission aims to assess the impact of Nasa’s 2022 asteroid collision test.
• Hera will reach the asteroid in 2026 to evaluate planetary defence techniques against potential threats.

On the way to investigate the scene of a historic asteroid collision, a European spacecraft swung by Mars and captured rare images of the red planet’s mysterious small moon, Deimos, the European Space Agency said on Thursday.

Europe’s Hera mission aims to find out how much of an impact a Nasa spacecraft made when it deliberately smashed into an asteroid in 2022, in the first test of our planetary defences.

But Hera will not reach the asteroid – which is 11 million kilometres from Earth in the asteroid belt between Mars and Jupiter – until late 2026.

On the long voyage there, the spacecraft slingshotted around Mars on Wednesday.

The spacecraft used the planet’s gravity to get a “kick” that also changed its direction and saved fuel, mission analyst Pablo Munoz said.

For an hour, Hera flew as close as 5600km from the Martian surface, at a speed of 33,480km/h.

It used the opportunity to test some of its scientific instruments, snapping about 600 pictures, including rare ones of Deimos.

The lumpy, 12.5km-wide moon is the smaller and less-well-known of the two moons of Mars.

Exactly how Deimos and the bigger Phobos were formed remains a matter of debate.

Some scientists believe they were once asteroids that were captured in the gravity of Mars, while others think they could have been shot from a massive impact on the surface.

The new images added “another piece of the puzzle” to efforts to determine their origin, Marcel Popescu, of the Astronomical Institute of the Romanian Academy, said.

It is hoped data from Hera’s HyperScout and thermal infrared imagers – which observe colours beyond the limits of the human eye – will shed light on this mystery by discovering more about the moon’s composition.

Those infrared imagers are why the red planet appears blue in some of the photos.

Bolstering planetary defence

Next, Hera will turn its focus back to the asteroid Dimorphos.

When Nasa’s Dart mission smashed into Dimorphos in 2022, it shortened the 160m-wide asteroid’s orbit around its big brother, Didymos, by 33 minutes.

Asteroid 2024 YR4 as observed by the Magdalena Ridge 2.4m telescope at the New Mexico Institute of Technology on January 27, 2025. Photo / AFP

Though Dimorphos itself posed no threat to Earth, Hera intends to discover whether this technique could be an effective way for Earth to defend itself against possibly existence-threatening asteroids in the future.

Space agencies have been working to ramp up Earth’s planetary defences, monitoring for potential threats so they can be dealt with as soon as possible.

This year, a newly discovered asteroid capable of destroying a city was briefly given a more-than-3% chance of hitting Earth in 2032.

However, further observations sent the chances of a direct hit down to nearly zero.

Richard Moissl, head of the European Space Agency’s (ESA) planetary defence office, said asteroid 2024 YR followed a pattern that would become more common.

As we get better at scanning the skies, “we will discover asteroids at a higher rate”, he said.

The ESA is developing a second planetary defence mission to observe the 350m-wide asteroid Apophis, which will fly just 32,000km from Earth on April 13, 2029.

If approved by the ESA’s ministerial council, the Ramses mission will launch in 2028, reaching the asteroid two months before it approaches Earth.

- Agence France-Presse