Japanese scientists are preparing a mission to Mars's moons to retrieve samples that could help unlock the origins of the Solar System and life on Earth. The mission aims to achieve the first round trip to the Martian system.

The unmanned Martian Moons eXploration (MMX) probe, developed in collaboration with US and European space agencies, universities and technology companies, could also help lay the groundwork for eventual human exploration.

The flagship H3 rocket carrying the MMX is set to launch from the Tanegashima Space Center at 4:41 a.m. Tuesday (1941 GMT Monday), according to the Japan Aerospace Exploration Agency (JAXA).

The spacecraft is expected to reach the vicinity of Mars a year later, where it will orbit the Martian moon Phobos for up to three years before landing and collecting at least 10 grams (0.35 ounces) of material from its surface.

A rover named IDEFIX, after the French name of Asterix's dog in the comic series, will first conduct surface observations to help ensure a safe landing.

"The sampling (from) Phobos is of course the world's first, but it means... this is the first round trip to the Martian system," MMX project manager Yasuhiro Kawakatsu told AFP.

JAXA said the mission will also investigate the possibility of using Phobos as a "natural space station" by establishing the requirements for a round trip to Mars, something "essential for crewed Mars exploration."

The spacecraft will also observe Mars's other moon, Deimos, although it will not land there, before returning to Earth.

Impact or capture

JAXA hopes the mission will reveal how Mars and its two moons formed, providing important clues to the origins of the Solar System.

One theory, known as the "giant impact" hypothesis, suggests that the Martian moons formed after a celestial body collided with Mars.

The alternative "capture" hypothesis proposes that the moons are asteroids captured by Mars's gravity.

Determining which theory is correct could help scientists understand "how a habitable environment for life might have arisen on the terrestrial planets," JAXA said, referring to Mercury, Venus, Earth and Mars, the four rocky planets closest to the Sun.

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

"If Phobos and Deimos are indeed remnants of these early delivery systems, they may hold clues to the origins of life itself, or, to be more correct, to the transport of the materials that were key to the emergence of life on rocky planets," he told AFP.

Deep in the 'gravity well'

MMX is a collaborative mission involving France's National Centre for Space Studies (CNES), the German Aerospace Center (DLR), NASA, the European Space Agency (ESA), and around 20 universities and technology companies.

Developing the spacecraft's landing legs has been particularly challenging because gravity on Phobos is extremely weak, according to JAXA scientists.

Japan's unmanned Smart Lander for Investigating Moon (SLIM), nicknamed the "Moon Sniper," tipped over after touching down on Earth's moon in 2024. However, it continued transmitting data and survived several two-week lunar nights.

Japan also has experience in retrieving samples from space. In 2020, JAXA's unmanned Hayabusa-2 mission returned 5.4 grams of rock and dust collected from an asteroid hundreds of millions of kilometers from Earth.

One key difference between JAXA's previous asteroid missions and MMX is that the new mission must travel close to Mars and then return to Earth, requiring the spacecraft to escape the planet's strong gravitational pull, Kawakatsu told reporters.

Phobos orbits approximately 6,000 kilometers above the Martian surface.

"Going deep into what we call the 'gravity well' is difficult," Kawakatsu said.

China's mission

US and Chinese space agencies have been competing to become the first to return samples collected from the surface of Mars to Earth.

NASA's Perseverance rover, which has been exploring the Red Planet since 2021, has already collected samples.

However, the US sample-return mission was effectively cancelled by the administration of President Donald Trump following a vote by the US Congress in January.

China, meanwhile, has announced plans to launch its Tianwen-3 spacecraft around 2028, with the aim of returning Martian samples to Earth as early as 2031, potentially before MMX returns.

JAXA scientists say samples from Phobos could offer a wider variety of material than those collected directly from Mars, particularly if the moon formed following a collision between a celestial body and the planet.