Japan's space agency, JAXA, is preparing to launch its Martian Moons eXploration (MMX) probe on a mission to collect the first-ever samples from Phobos, one of Mars' two moons, and return them to Earth. The mission could help settle a long-standing debate about how Phobos and Deimos formed, either from debris after a massive collision with Mars or as captured asteroids from the outer solar system, by comparing the samples with material already gathered from the Martian surface itself.

The 4,480-kilogram spacecraft will take roughly a year to reach Mars, spend three years operating in the Martian system, and then take another year to return, with samples expected on Earth in 2031. Landing on the tiny, 11-kilometre-radius Phobos poses major challenges given its weak gravity, so the probe relies on high-precision autonomous navigation rather than remote control from Earth, where signal delays can reach 20 minutes. A French-German rover called IDEFIX will scout the surface ahead of landing, after which a robotic arm and a NASA-designed nitrogen-gas device will gather rock and dust samples, some of which scientists believe may include material blasted off Mars itself by past meteorite impacts.