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Japan set to launch world-first mission to collect samples from Martian moon Phobos

The MMX spacecraft will take five years to return samples that could explain the origins of Mars's moons and aid future crewed exploration.

NewsJaws DeskEditorial desk

Published 18 Oct 2026, 09:34 BST3 min read

A potato-shaped, cratered grey-brown moon against black space, with long parallel grooves across its surface and shadowed craters on its upper left edge. — File photo: Phobos, the larger of Mars's two moons, imaged in colour by the HiRISE camera on NASA's Mars Reconnaissance Orbiter on 23 March 2008. Phobos colour 2008 — NASA / JPL-Caltech / University of Arizona (resized and converted to WebP). Public domain.Image source Image licence: Public domain

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Japan is preparing to launch a spacecraft on the world’s first mission to return samples from Phobos, one of Mars’s two small, potato-shaped moons. The Japan Aerospace Exploration Agency (JAXA) aims to launch the Martian Moons eXploration (MMX) spacecraft on Tuesday at 4:41 am from the Tanegashima Space Centre aboard a new H3 rocket.

Scientists hope the five-year mission will reveal how Phobos and its smaller sibling Deimos formed, and possibly shed light on the origins of life in the solar system. The launch comes as the US, China and others consider sending astronauts to Mars.

The spacecraft will arrive near Mars one year after launch, orbit Phobos for up to three years, then land and collect at least 10 grams of material from the surface. A rover named IDEFIX will first conduct surface observations to ensure a safe landing. JAXA says the mission will also explore using Phobos as a “natural space station” by establishing requirements for a round trip to Mars, which it calls essential for crewed Mars exploration. The spacecraft will observe Deimos, but not land on it, before returning to Earth.

MMX project manager Yasuhiro Kawakatsu said the sampling from Phobos would be the world’s first and would make this the first round trip to the Martian system. He added that despite their potential importance, Martian moons have never been fully investigated, describing them as “the most important unclimbed mountains in the solar system.”

Two competing theories explain the moons’ origins: the “giant impact” hypothesis suggests they formed after a celestial body collided with Mars, while the “capture” hypothesis postulates they are asteroids captured by Mars’s gravity. Scientists chose Phobos because it is closer to Mars than Deimos and may hold more information about the planet. Material from Mars is expected to make up about 0.1% of the material collected from Phobos, according to JAXA officials.

Landing on Phobos presents unique challenges due to its low gravity. To minimise bouncing at touchdown, the MMX exploration module is equipped with four-legged landing gear with shock absorption. The rover’s wheels are designed to get traction in low gravity, right themselves if the rover tips over, and move “at a snail’s pace”, according to JAXA. Multiple Russian attempts to land on Phobos, including one in 2011, have failed.

The samples will be stored in a heat-protected capsule designed to survive reentry into Earth’s atmosphere. The module is expected to land in Australia before being sent back to Japan. Kawakatsu said samples from Phobos would give scientists useful data for considering a Martian moon as a base for a future manned mission to Mars.

International competition

Japan leads the international mission, which includes equipment and communications support from NASA and other national space agencies. China, meanwhile, has announced its Tianwen-3 spacecraft is scheduled for launch around 2028 and hopes to return Mars samples to Earth as early as 2031 — potentially before the MMX’s return. Phobos is about 27km across at its widest point and orbits Mars at a distance of about 6,000km three times a day.