Japan launches MMX spacecraft to retrieve soil from Mars moon Phobos

International collaboration for the $578 million MMX project

Five of the world’s space agencies have teamed up for the five-year MMX mission. This $578 million project features a 5-ton spacecraft that is a collaboration between JAXA, United States and European space agencies, and various universities and tech companies. NASA provided instruments and technologies to assist the mission.

The spacecraft is expected to reach Mars by late next summer. It will arrive near the planet around August next year, where it will orbit Phobos for three years to collect at least 10g (0.35 ounces) of material from the surface. The mission aims to be the first round trip to the Martian region.

Scientific goals to determine moon formation

Phobos is a lumpy, potato-shaped rock measuring approximately 14 miles (F8) or 22 kilometers (F18) across. Scientists do not know exactly how the moon formed, with theories suggesting it could be an asteroid or debris left over from the formation of the solar system about 4.5 billion years ago.

The Japan Aerospace Exploration Agency intends to use the mission to determine if the Martian moons formed via a giant impact, where a body collided with Mars, or the capture hypothesis, where the moons were pulled in by gravity. Examining pieces of the moon can explain how Mars’ moons and possibly moons elsewhere came to be.

French astrophysicist Patrick Michel said the mission will shed light on transport mechanisms that delivered water, volatiles, and organic compounds from the outer solar system to the inner rocky planet region. Michel said these processes may have played a key role in making these worlds habitable.

Michel noted that if Phobos and Deimos are remnants of these early delivery systems, they may hold clues to the origins of life or the transport of materials key to the emergence of life on rocky planets.

Idefix rover to scout the surface of Phobos

A French-German rover named Idefix will scout the surface of Phobos. Named after the dog from the Asterix comics, the rover is no larger than a microwave oven and will be the first vehicle to travel across the moon.

Idefix will move at a speed of 1 millimeter per second while conducting surface observations for 100 days to ensure a safe landing. The rover is designed to right itself if it lands upside down, according to Julien Baroukh of the French Space Agency.

Baroukh said the rover will lose this self-righting capability once its solar panels are deployed.

Historical context of Martian exploration

NASA has landed nine spacecraft on Mars over the past 50 years, and China achieved a touchdown in 2021. Despite these efforts, no mission has ever reached Mars's moons, Phobos or Deimos. No spacecraft has successfully returned samples from Mars or its moons.

Japan has two asteroid sample returns already under its cosmic belt. US astronomer Asaph Hall discovered Phobos and its smaller sibling, Deimos, in 1877. The name Phobos originates from the ancient Greek word for fear, and Deimos originates from the ancient Greek word for dread.

Timeline for sample collection and return

The mission is scheduled to reach Phobos in August 2027 and will spend at least 16 months surveying the surface. The spacecraft will observe Deimos during the mission, though it will not land on the moon.

A stationary lander will collect at least 10 grams of material from Phobos in late 2028 or 2029. The collected samples are expected to return to Earth in 2031, landing in the Australian desert.

Reactions from mission leadership and scientists

JAXA project manager Yasuhiro Kawakatsu said the sampling of Phobos is the world's first, marking the first round trip to the Martian system. Makoto Arita, project manager of the JAXA H3 rocket team, said, "Being able to be involved in such a grand mission is incredibly exciting".

JAXA scientist Mari Aida said, "I'd dreamt of this day, so I'm incredibly happy," and "Right now I feel really relieved". NASA astrophysicist Tom Statler said, "There’s a lot of adrenaline and a lot of excitement and a lot of wow".

Nicky Fox, associate administrator and Science Mission Directorate at NASA, said, "The samples from MMX will bring forth paradigm-shifting science on the Mars system for generations to come, especially as NASA prepares to send the first humans to Mars".

Spacecraft unveiled at Tanegashima

The Japan Aerospace Exploration Agency unveiled the spacecraft for the Martian Moons eXploration mission at the Tanegashima Space Center in Minamitane, southwestern Japan, on Aug. 13, 2026.