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Japan is preparing to launch a mission to Mars's moons to bring back samples from the Martian system for the first time, according to the Japan Aerospace Exploration Agency (JAXA).
The unmanned Martian Moons eXploration (MMX) probe is scheduled to lift off from the Tanegashima Space Center aboard the flagship H3 rocket on Tuesday, Oct. 20, at 4:41 am local time (1941 GMT on Monday), JAXA said.
The spacecraft will arrive near Mars about a year later and orbit the moon Phobos for up to three years before landing to collect at least 10 grams (0.35 ounces) of surface material.
A rover named IDEFIX, the French name of the dog of comic hero Asterix, will first conduct surface observations to help ensure a safe landing. The probe will also observe the other Martian moon, Deimos, without landing, before returning to Earth.
MMX is a collaboration involving France’s National Center for Space Studies (CNES), the German Aerospace Center (DLR), NASA, the European Space Agency (ESA) and about 20 universities and technology companies.
Project manager Yasuhiro Kawakatsu told AFP that the Phobos sample is a world first and marks the first round trip to the Martian system.
JAXA said the mission will also examine whether Phobos can serve as a “natural space station” by establishing the requirements for a round trip to Mars, which the agency described as essential for crewed Mars exploration.
JAXA aims to learn how Mars and its two moons formed, a key piece of knowledge for understanding how the Solar System formed.
One theory, known as the giant impact hypothesis, holds that the moons formed after a celestial body collided with Mars. The capture hypothesis proposes that Mars's gravity captured the moons from asteroids.
JAXA said determining which theory is correct will help reveal “how a habitable environment for life might have arisen on the terrestrial planets," referring to the four rocky worlds closest to the Sun: Mercury, Venus, Earth and Mars.
Patrick Michel, a French astrophysicist working on IDEFIX, said MMX will shed light on the transport mechanisms that delivered water, volatiles and organic compounds from the outer Solar System to the inner rocky planets, processes that may have helped make those worlds habitable.
He told AFP that if Phobos and Deimos are remnants of these early delivery systems, they may hold clues to the transport of materials key to the emergence of life on rocky planets.
JAXA scientists say sand and rocks from Phobos may offer a wider variety of samples than those on the planet itself, especially if the moon formed through a collision between a celestial body and Mars.
JAXA scientists say developing the spacecraft’s landing legs was particularly difficult because Phobos's gravity is extremely weak. Phobos orbits about 6,000 kilometers above the Martian surface.
Kawakatsu told reporters that, unlike in JAXA’s past asteroid missions, “we have to travel very close to Mars and return," which means escaping the planet’s heavy gravity. “Going deep into what we call the ‘gravity well’ is difficult,” he said.
Japan has experience in returning samples from space. In 2020, the unmanned Hayabusa-2 probe brought back 5.4 grams of rock and dust from an asteroid several hundred million kilometers from Earth.
In 2024, Japan’s unmanned Smart Lander for Investigating Moon (SLIM), nicknamed the “Moon Sniper," tipped over after landing on Earth’s Moon but still transmitted data and survived several two-week lunar nights.
US and Chinese space agencies have raced to be the first to return rock samples from Mars's surface to Earth. NASA’s Perseverance rover, which has been roaming the Red Planet since 2021, has already collected samples.
However, the Trump administration effectively canceled the mission after a vote by the U.S. Congress in January.
China has announced that its Tianwen-3 spacecraft is scheduled to launch around 2028 and aims to return Mars samples to Earth as early as 2031, potentially before MMX returns.
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