TANEGASHIMA SPACE CENTER, Japan (AFP) — Japanese scientists are readying a mission to Mars' moons to retrieve samples that may unlock the origins of the Solar System and life on Earth, although a rival Chinese mission aims to make it back first.

The unmanned Martian Moons eXploration (MMX), set to blast off from Tanegashima Space Center in the coming months, could also lay the groundwork for humans visiting the red planet.

The spacecraft, revealed to media last Thursday, will stay in Mars' orbit for around three years and will attempt to land on Phobos.

It will collect at least 10 grams of material from the surface of Phobos, while the IDEFIX rover — the French name for comic hero Asterix's dog — will conduct surface observations.

The spacecraft will also observe Demios, the other of Mars' moons — but without landing — before a return capsule heads back to Earth to land in Australia in around 2031.

The Japan Aerospace Exploration Agency (JAXA) hopes that the mission will reveal how Mars and its moons formed, a key piece of knowledge in working out how the Solar System was born.

One theory for the origin of the Martian moons — the "giant impact" hypothesis — is that they formed after a celestial body collided with Mars.

The "capture" hypothesis meanwhile postulates that the moons are asteroids from the outer Solar System that were captured by Mars' gravity.

Determining which is right will help reveal "how a habitable environment for life might have arisen on the terrestrial planets," JAXA said, referring to the four rocky worlds closest to the Sun — Mercury, Venus, Earth and Mars.

"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.