Rover on the home stretch to the martian moon Phobos

"We are very excited to collaborate with CNES and DLR as part of the MMX mission, which endeavours to clarify the origin of the martian moons and the evolutionary process of the martian sphere by collecting samples from one of Mars' two moons – Phobos – for the first time in space history," said Hiroshi Yamakawa, President of JAXA. He added: "Japan shares a precious memory with France and Germany regarding the collaboration during the Hayabusa2 sample return mission, on which the joint CNES-DLR MASCOT lander flew. And we are looking forward to putting our efforts together once again for a successful MMX mission."

On the occasion of the signing, Anke Kaysser-Pyzalla, Chair of the DLR Executive Board, said: "Japan and France are important strategic partner countries for DLR in almost all of our research areas. In this context, our cooperation within the framework of the MMX mission is a specific example of the creative power of our multifaceted collaboration. When a rover travels over the surface of the martian moon Phobos for the first time, we will have jointly pushed technological boundaries to learn more about the origin of the Solar System and Mars with its moons."

Walther Pelzer, DLR Executive Board Member and Director General of the German Space Agency at DLR emphasised: "MMX is a true example of how to conduct challenging space missions with international cooperation – as a joint undertaking, together with likeminded nations, space agencies and partners. Each side brings fruitful and specific competences, sharing costs and risks and gaining exceptional technological expertise and scientific results."

"The signing of this new tripartite agreement between CNES, JAXA and DLR is another milestone in the fruitful cooperation between our three nations on the MMX mission. By studying the two martian moons, Phobos and Deimos, this mission will lead to major advances in the knowledge of the Solar System," says Philippe Baptiste, CNES' CEO.

The final work to complete the rover is currently under way at the CNES site in Toulouse. In the last few months, the final integration of all instruments and subsystems, including the solar arrays, power system, on-board computer and radio system for contact with the MMX spacecraft, has taken place there. Previously, DLR had already integrated the rover's carbon-reinforced composite chassis, including the locomotion system, at their Bremen site and delivered it to CNES in Toulouse in November 2022. The miniRAD radiometer and the RAX spectrometer from DLR's Berlin site were also shipped to Toulouse. In addition to the two DLR instruments for analysing the thermal properties and mineralogical composition of the surface, CNES has installed two cameras that monitor the wheels and the ground. CNES has also developed and integrated the two navigation cameras that will be used for the navigation.

The MMX spacecraft consists of three modules. The exploration module has landing legs, samplers and some instruments as well as the MMX rover on board. The exploration module is connected to the return module with the sample return capsule, which in turn is connected to a propulsion module housing propellant tanks and thrusters. The MMX spacecraft design has been completed, and the project team has started the final manufacture, testing and integration of the spacecraft including instruments provided by partner agencies toward the launch target in FY2024.

The mission timeline

The launch of the mission is scheduled for the mid-2020s. After a journey of approximately one year, MMX will reach Mars and enter orbit. Then, the eight scientific instruments on the exploration module will begin mapping and characterising the surfaces of Phobos and Deimos. During the course of the mission, the rover is scheduled to land on Phobos. This will involve setting the rover down from an altitude between 40 and 100 metres above the surface. After landing, the rover will autonomously upright itself and then become operational. The measurement phase will then begin; this will last about three months, during which the rover will approach various targets that are of interest for scientific analysis. Towards the end of the mission, ground samples will be collected by the mother spacecraft, taking into account the knowledge acquired using the rover. These will be delivered back to Earth in the return module for more detailed analyses.

The origin of fear and terror

In Greek mythology, Phobos and Deimos were the companions of Ares, the god of war, who in Roman antiquity had his counterpart in Mars, also a god of war. They were discovered in 1877 by the American astronomer Asaph Hall. Due to their small size (Phobos is 27 kilometres in its largest diameter and Deimos 15 kilometres), both moons are irregularly shaped and resemble asteroids. Thus, one theory is that Mars simply captured the two moons in the past, which possibly originated from the asteroid belt. However, both moons orbit Mars near the ecliptic plane on which all planets and most of their moons move around the Sun. In addition, both orbits are almost circular. Such a coincidence would be difficult to account for under the 'captured asteroids' theory. This could be explained if Phobos and Deimos were remnants of a huge asteroid impact on Mars.

• MMX – Martian Moons eXploration
• Cover story from DLRmagazine 172: The MMX rover will explore the mysterious martian moon Phobos - Head over heels into adventure

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