The planetary defense hera surveys Mars and captures images of Deimos, its most enigmatic moon

The Mission of Planetary Defense Hera of the European Space Agency (ESA) exceeded the Mars system, a maneuver to shoot the ship to the deep space in the direction of Asteroid Dimorphos, 11 million km from the earth. During his approach, Hera was able to capture “splendid images” in high resolution of the surface of the red planet and the hidden face of Deimos, the smallest and mysterious of his two moons.

Throwed on October 7, 2024, Hera, the size of a car, will study in detail Dimorphos, the first asteroid whose orbit has been altered by human action. In 2022 a NASA probe called Dart hit the space rock, just 160 meters in diameter, to know if this kinetic technique is useful in case some dangerous asteroid threatens the earth in the future. The probe will scrutinize how the impact and its consequences occurred. According to ESA, their data will contribute to “converting asteroid deviation into a well -known and potentially repeatable technique.”

Hera’s overflight on Mars was an integral part of her cruise phase for deep space, designed by the ESA flight dynamic team. As he approached only 5,000 km from the planet, his gravity diverted the trajectory of the probe to his final destination, the Didymos binary asteroid, composed of the rock of the same name, 780 meters long, and his moon Dimorphos. This maneuver shortened its travel time in several months and saved a substantial amount of fuel.

Moving 9 km/s with respect to Mars, Hera obtained images of Deimos, from just 1,000 km away, observing the opposite face of the moon. From 12.4 km in diameter, we orbit from approximately 23,500 km from the surface of Mars and is in synchrony with the tides, so this face of the moon is rarely seen. Dust cover, this Martian moon has an uncertain origin. “The images will help us to know if it is the remnant of a giant impact on Mars or a captured asteroid,” says Caglayan Guerbuez, Mission Operations Manager.

“Our Mission and Flight Dynamics Analysis team in Esoc (Germany) did an excellent job by planning gravitational assistance,” says Guerbuez. “Especially because they were asked to refine the maneuver to take Hera near Deimos, which generated enough extra work!”

During the overfruit, Hera used her 1020×1020 asteroid framing camera in black and white, which acquires images in visible light; The hyperspectral image generator Hyperscout H, which observes in a range of colors beyond the limits of the human eye, in 25 visible spectral bands and nearby infrared, to characterize the mineral composition; and the infrared thermographic chamber, supplied by the Japanese Aerospace Exploration (Jaxa), which captures images in average infrared wavelengths to graph the surface temperature graphically, revealing physical properties such as roughness, the distribution of the size of the particles and the porosity.

“These instruments have been tested before, during the earth’s departure, but this is the first time we use them on a small and distant moon from which we still lack knowledge, with possibly interesting results,” says Michael Kueppers, a scientist of the mission.

As explained by the main researcher of Hera, Patrick Michel, director of Research at the CNRS/Observatory of the Costa Azul, “other hera instruments that we will use once we reach the asteroids Deimos and Dimorphos were not activated because they are not usable at such a long distance and such fast speed from an objective (such as our Palt laser altimeter, with a maximum range of 20 km) or because they are on board the pair of cubes Hera, (two small satellites) that will only be displayed in the asteroids ».

Hera also made some joint observations of Deimos with the Mars Express probe of ESA, which has been in orbit around the red planet for more than two decades.

The results of the close meeting with Deimos should help guide the operational planning of the Mission of Exploration of the Marcian moons next year, MMX, directed by the Japanese Aerospace Exploration Agency (Jaxa) in collaboration with NASA, the French Space Agency CNES, the German Aerospace Center (DLR) and ESA. MMX will not only collect detailed measurements of both Martian moons, but also land in phobos to collect a sample and return it to the earth for analysis.

Hera’s twin destinations are much smaller than the moon deimos, the size of a city, but Hera goes towards them. A series of lit of “impulsive encounter” from October 2026 will refine their course to reach the Didymos system in December.

«This has been the first and exciting exploration experience of the Hera team, but not the last. In 21 months, the probe will reach the objective asteroids and the investigation of the place of the impact of the sole object of our solar system whose orbit has been appreciably altered by human action, ”says Ian Carnelli, director of the Hera Mission.