Off to the moons of Mars – MMX mission and Idefix® rover ready for launch

"Our rover Idefix® and the MMX spacecraft of our Japanese collaborators are beginning their journey into the Mars system as a single unit. Only at Phobos will their paths separate. There, Idefix® will make history – as the first rover ever to leave tracks on a moon of Mars," says DLR project leader Markus Grebenstein and CNES project leader Julien Baroukh.

Idefix® – German-French rover for the Martian moon Phobos

As early as 2022, DLR completed the partially assembled Idefix® rover and two instruments. It was then fully assembled at the French space agency CNES in Toulouse, and further instruments and components were added. After completion in July 2023, Idefix® successfully underwent space qualification testing. The focus was on its flawless functioning, as well as its resistance to the vibrations of a rocket launch and to the extreme temperatures on Phobos, ranging from minus 170 degrees Celsius to 70 degrees Celsius. From 2024, the rover began to be integrated into the MMX mothership in Japan. In August 2026, JAXA presented the completed space probe to the public. Idefix®, roughly the size of a crate of drinks, could clearly be seen in its travel position between the probe's landing legs. What makes the Idefix® rover special is its extremely compact design. Idefix® essentially has all the elements of a fully fledged science rover, but thanks to its highly integrated construction, it has a mass of just 25 kilograms. Owing to its low weight and Phobos' low gravity, Idefix® will be able to land directly on the surface without the help of a landing vehicle.

Around the turn of 2028/2029, the MMX mothership is expected to release the Idefix® rover into free fall towards Phobos from a height of approximately 40 metres above the surface. Once it has landed, it will right itself autonomously and will then be ready for the roughly three-month mission phase on the Martian moon. On the surface, Idefix® will specifically search out and analyse scientifically interesting areas of Phobos. In doing so, Idefix® is breaking new technical ground, as no wheeled exploration vehicle has ever driven on a celestial body with gravity of less than a thousandth that of Earth. The rover's preliminary survey of the surface will also later help ensure that the mothership is as well prepared as possible to land on Phobos to collect samples.

The launch of the MMX mission is scheduled for 19 October 2026, with a 19-day launch window to Mars. After a flight of approximately one year, the MMX probe will reach Mars in the second half of 2027 and enter orbit around the planet. The exploration module's eight scientific instruments will then begin mapping and characterising the surfaces of Phobos and Deimos. To meet the mission's extensive requirements, the Japanese space agency JAXA has opted for a three-module design for the probe – the most massive Japanese interplanetary space probe to date: a powerful propulsion module handles the transfer to Mars and braking manoeuvres there; an exploration and landing module carries the scientific instruments, including telescope cameras, spectrometers and the German-French rover Idefix®; and a return module, including the re-entry capsule with its thermal protection shields, brings the probe back to Earth.

Where did 'fear' and 'terror' come from?

Besides our Moon, Phobos and Deimos are the only other two moons in the inner Solar System. They are much smaller than the Moon and not spherical, but irregularly shaped. Phobos has a maximum diameter of just under 27 kilometres, while Deimos measures just 15 kilometres. Both moons of our neighbouring planet were named Phobos and Deimos after their discovery in 1877 by the American Asaph Hall. In Homer's 'Iliad', they are two brothers who accompany Ares, the Greek god of war (the equivalent of Mars, the Roman god of war). Approximately 150 years after their discovery, the origin of the Martian moons remains an open question: are they captured asteroids, or did they form after a massive meteorite impact on Mars? MMX aims to help answer this question and uncover the history of Phobos and Deimos.

The formation of the Martian system is also key to better understanding the processes of planet formation in the Solar System as a whole. In any case, traces of Martian rock are likely to be found on the surface of Phobos, having landed there as ejected material from later asteroid impacts on Phobos. This means that, together with the samples from Phobos, material from Mars could also make its way to Earth in the return capsule – and from there into terrestrial laboratories.

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