Japanese scientists are preparing to launch a major mission to Mars’ moons that could provide important clues about the origins of the Solar System and the materials that may have contributed to life on Earth. However, China’s planned Mars sample-return mission could potentially complete the journey first.
The Martian Moons eXploration (MMX) mission, led by the Japan Aerospace Exploration Agency (JAXA), is expected to launch from the Tanegashima Space Centre in the coming months. The unmanned spacecraft will spend about three years around Mars and attempt to land on Phobos, one of the planet’s two moons.
MMX will collect at least 10 grams of material from Phobos, while the French-built Idefix rover will examine the moon’s surface. The spacecraft will also study Mars’ other moon, Deimos, without landing on it. A return capsule is expected to bring the collected samples back to Earth, landing in Australia around 2031.
Searching for the Moons’ Origins
Scientists hope the mission will help determine how Mars and its moons formed, which could also shed light on the early history of the Solar System.
One possibility, known as the “giant impact” theory, suggests that Phobos and Deimos were created from material ejected when another celestial body collided with Mars. Another theory proposes that the moons are asteroids originating farther out in the Solar System that were later captured by Mars’ gravity.
Understanding their origins could help scientists determine how water, organic compounds and other materials were transported toward the inner planets, potentially contributing to the development of habitable environments.
French astrophysicist Patrick Michel, who is involved with the Idefix rover, 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 planet region — processes that may have played a key role in making these worlds habitable.”
He added, “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.”
JAXA also hopes the mission will help establish whether Phobos could eventually serve as a “natural space station” for future Mars exploration. The technology developed through MMX could support round trips between Earth and Mars as space agencies work toward crewed missions.
Challenging Landing
MMX is being developed through cooperation between Japan, France, Germany, Nasa, the European Space Agency and various universities and technology companies.
Landing on Phobos presents major engineering challenges because its gravity is extremely weak. Engineers must design landing legs capable of absorbing the impact while preventing the spacecraft from bouncing or falling over.
Japan has already gained experience with difficult landings through its Smart Lander for Investigating Moon (SLIM), known as the “Moon Sniper”. Although the spacecraft tipped over after landing on the Moon in 2024, it continued transmitting scientific data and survived several lunar nights.
Japan also has extensive experience in returning extraterrestrial samples. Its Hayabusa-2 spacecraft successfully brought 5.4 grams of rock and dust from an asteroid back to Earth in 2020.
Race to Return Mars Samples
Japan is not alone in pursuing Mars sample-return technology. Nasa’s Perseverance rover has been collecting samples on Mars since 2021, but plans to return them to Earth have faced major setbacks and effectively been cancelled following decisions by the Trump administration and Congress.
China is also preparing its Tianwen-3 mission, which is currently planned for launch around 2028. Beijing aims to return samples from Mars to Earth around 2031, potentially beating Japan’s MMX mission in bringing Martian-system material back to Earth.
China previously demonstrated its growing Mars capabilities when the Tianwen-1 mission successfully delivered the Zhurong rover to the Martian surface in 2021.
