Japan’s MMX probe will sample a Martian moon
JAXA launched its Martian Moons Exploration spacecraft on October 19 to investigate Phobos and Deimos. The mission will orbit Mars, map Phobos, deploy a small rover, land to collect about 10 grams of surface material, and return the sample to Earth in 2031. Its main goal is to determine how the two Martian moons formed.
MMX will spend about a year reaching Mars, then orbit near Phobos to map its shape, seek landing sites, and occasionally view Deimos from afar. Phobos is roughly 26 kilometers long and Deimos about 16; both were discovered in 1877, yet their origin remains unknown.
The French-German Idefix rover, roughly 24 kilograms and shoebox-sized, will be released 40 to 100 meters above Phobos. In the moon’s weak gravity—about one-thousandth of Earth’s—it may drift down for several minutes, land gently, and right itself. It is designed to measure surface temperature and minerals and photograph its wheel tracks.
MMX’s sample return could give planetary scientists a direct way to test competing ideas about the moons’ origins, shaping future Mars-system research. The mission may also strengthen Japan’s role in robotic exploration and give European partners experience with a small rover. Public interest in sample-return missions could grow, while the results may inform how agencies plan ambitious, multi-step missions.