Off to the Martian moons MMX Mission and Idefix® Rover Ready for Launch

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German Aerospace Center DLR

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Japan’s MMX mission is set to launch in October 2026, carrying the German-French Idefix® rover on a pioneering journey to Mars and its moons.

The MMX (Martian Moons eXploration) spacecraft will launch for Mars on October 19, 2026, at 9:41 p.m. CEST. The Japanese space agency Japanese Aerospace Exploration Agency (JAXA) recently announced the date. It is the largest Japanese mission to the solar system to date: for the first time ever, it will land on the Martian moon Phobos and, in 2031, bring the first-ever samples from Phobos and thus from the Martian system back to Earth. An important part of the mission is the German-French Idefix® rover, which will become the first lander ever to touch down on Phobos in 2029, in order to explore its surface at close range for 100 days.

In August, JAXA presented the completed spacecraft, including the mounted rover, to the public at the spaceport in Tanegashima in the presence of the German Aerospace Center (DLR). DLR and the French space agency CNES (Centre National d’Études Spatiales) jointly provided Idefix®. The final launch preparations are now under way, including mounting the spacecraft on JAXA’s new, powerful H3 rocket, which will carry MMX to the Martian system. The launch window to Mars extends until November 7, 2026.

“Our Idefix® rover and the MMX spacecraft of our Japanese partners will begin their journey to the Martian system as one unit. Only at Phobos will their paths diverge. There, Idefix® will make history—as the first rover ever to leave tracks on a Martian moon,” said DLR Project Manager Prof. Markus Grebenstein and CNES Project Manager Julien Baroukh.

Idefix®—a German-French rover for the Martian moon Phobos

DLR completed the partially assembled Idefix® rover and two instruments as early as 2022. It was subsequently fully assembled at the French space agency CNES in Toulouse (Germany) and supplemented with additional instruments and components. After completion in July 2023, Idefix® successfully underwent space qualification tests. The focus was on ensuring flawless operation and resistance to the vibrations experienced during rocket launch, as well as the extreme temperatures on Phobos, ranging from minus 170 to 70 degrees Celsius (approx. minus 274 to 158 degrees Fahrenheit). From 2024 onwards, the rover was integrated into the MMX mother spacecraft in Japan. 

In August 2026, JAXA presented the completed spacecraft to the public. The approximately beverage-crate-sized Idefix® was clearly visible in its cruise position between the spacecraft’s landing legs. What makes Idefix® particularly special is its extremely compact design. Idefix® essentially contains all the elements of a fully fledged scientific rover, yet thanks to its highly integrated design, it has a mass of only 25 kilograms (approx. 55 pounds). Due to its low weight and the low gravity, Idefix® will be able to land directly on Phobos without the assistance of a landing vehicle.

Around the turn of the year 2028/2029, the MMX mother spacecraft is expected to release the Idefix® rover from an altitude of approximately 40 meters (approx. 131 feet) above the surface, sending it into free fall towards Phobos. Once it has landed, it will right itself autonomously and will then be ready for the approximately three-month mission phase on the Martian moon. On the surface, Idefix® will specifically search for and analyse scientifically interesting areas of Phobos. In doing so, Idefix® will break new technological ground, as no wheeled exploration vehicle has ever driven on a celestial body with less than one-thousandth of Earth’s gravitational force. The rover’s preliminary exploration of the surface will also help prepare the mother spacecraft for a landing on Phobos at a suitable location for sample collection.

“More than a decade ago, we began the MMX journey. Despite countless challenges, the dedication and ingenuity of scientists and engineers throughout Japan and around the world have brought us to this moment. The launch of MMX will be an emotional milestone for all of us,” said Dr. Yasuhiro Kawakatsu, MMX Project Manager at JAXA.

MMX—a Japanese spacecraft for exploring the Martian moons

The launch of the MMX mission is scheduled for October 19, 2026, with the launch window to Mars lasting 19 days. After approximately one year of flight, the MMX spacecraft will reach Mars in the second half of 2027 and enter its orbit. The eight scientific instruments on the exploration module 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 spacecraft design, making MMX the heaviest Japanese interplanetary spacecraft to date: a powerful propulsion module will provide the transfer and braking manoeuvres at Mars, an exploration and landing module will carry the scientific instruments, including telescope cameras, spectrometers and the German-French Idefix® rover, while a return module will include the sample-return capsule with its thermal shields for the journey back to Earth.

Where did “fear” and “terror” come from?

Phobos and Deimos are, alongside Earth’s Moon, the only two moons in the inner solar system. They are much smaller than Earth’s Moon and are not spherical, but irregularly shaped. Phobos has a maximum diameter of just under 27 kilometres (approx. 17 miles), while Deimos measures only 15 kilometres (approx. 9 miles). The moons Phobos and Deimos received their names, meaning “fear” and “terror”, respectively, after their discovery in 1877 by American astronomer Asaph Hall. In Homer’s Iliad, they are two brothers accompanying the Greek god of war Ares (the Roman god of war Mars). Around 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 is intended to help answer this question and shed light on the history of Phobos and Deimos.

The formation of the Martian system is also a key to gaining a better understanding of the processes involved in planet formation throughout the solar system. In any case, traces of Martian rocks are likely to be found on the surface of Phobos, having landed there as ejecta from later asteroid impacts on Phobos. This means that the Phobos samples could also contain material from Mars, which could then be transported to Earth in the return capsule and made available for analysis in terrestrial laboratories.