Japan launches mission to make first return trip to Mars

Japan’s MMX mission is designed to make the first round trip to the Martian system and bring samples of Phobos, one of Mars’ two small moons, back to Earth. An H3 rocket is scheduled to launch the 4,480-kilogram spacecraft from Tanegashima; the journey will take about a year each way, with three years spent collecting data. The probe will also deploy Idefix, a small rover to explore Phobos. The mission has gained importance as NASA’s separate Mars sample-return programme was cancelled over costs and budget cuts. Japan has experience retrieving asteroid samples through its Hayabusa missions and is deliberately pursuing a capability the US has not yet achieved.

The samples could help resolve whether Phobos and Deimos are captured asteroids or debris from a major impact on Mars. If they formed in a collision, Phobos may contain ancient Martian material; if it is an asteroid, it could preserve evidence about water- and life-supporting ingredients delivered to the inner solar system. Either way, researchers see the material as a record of early planetary conditions, though it cannot replace samples collected by NASA’s Perseverance rover. The mission also offers a test of travel to and from Mars’ orbit, relevant to future crewed expeditions. Its prospects depend on demanding engineering: the launch window comes only every 26 months, the H3 rocket has failed twice in nine attempts, and Phobos’ weak gravity and uncertain surface make landing difficult.