JAXA Phobos Sample Mission Set for October 20 Launch on H3 Rocket

The Martian Moons eXploration mission will lift off aboard an H3 rocket from the Tanegashima Space Center at 04:41 JST on October 20, 2026. MMX will be the first mission to collect a sample from Mars's moon Phobos and bring it back to Earth, a planetary-science first.

Mars has two moons, Phobos and Deimos, which remain poorly understood despite the many missions sent to the Red Planet. No spacecraft has dwelled near them for long, leaving open the question of their origin. They may be asteroids captured into Mars orbit, or the remnants of debris thrown up by a giant collision on the planet's surface. Collecting samples is intended to settle that question.

MMX is led by the Japan Aerospace Exploration Agency in collaboration with NASA, France's CNES, the German Aerospace Center DLR, and the European Space Agency. The mission will be the first spacecraft to orbit Phobos, the first to land on a moon other than Earth's own, and the first to collect samples from Phobos's surface. Special technology was developed to land, manoeuvre, and collect samples robotically in the extremely low gravity at Phobos. After completing those tasks, MMX will become the first mission to return to Earth after visiting the Mars system.

The mission carries 11 science instruments, seven on the main spacecraft and four on a rover named Idefix. The main spacecraft also carries a radiation monitor, two high-resolution cameras, and two sampling devices. The 25-kg Idefix rover will prepare for the main spacecraft's sample-collection landing and analyse the composition and texture of Phobos's surface. Gravity on Phobos is so low that Idefix will weigh the equivalent of 15 grams on its surface.

MMX will take about a year to reach Mars, entering orbit around the planet in August 2027 and orbiting Phobos from September 2027. After studying Phobos and Deimos from a distance, MMX will release Idefix in early 2029. In 2030, the main spacecraft will land on Phobos to collect samples and pack them into a return module. That module is set to arrive back at Earth in 2031 and deliver at least ten grams of Phobos material in a sample return capsule, which will land in Australia before being transferred to Japan for extraction, cataloguing, and sharing with mission partners.

"The data and samples returned by MMX are a window to study the evolution of Mars and the Solar System," says Elliot Sefton-Nash, ESA MMX Project Scientist. Conditions on Mars may once have been suitable for life, and the mission is expected to shed light on how Earth and the rest of the Solar System formed and evolved. "Bringing samples to our most sophisticated labs here on Earth is a multiplier for discoveries, because our most precise instruments are too large, complex or sensitive to send to space," Sefton-Nash adds. "Even after the mission has been completed, future generations of scientists will study the Phobos samples with even more advanced instruments."

ESA's Mars Express spacecraft, confirmed to operate at Mars until at least 2029, may support MMX's observations, while the upcoming ExoMars Rosalind Franklin rover will complement the mission by collecting and analysing samples from Mars's subsurface. Samples are planned to be made available to European scientists, with ESA working alongside CNES, DLR, and JAXA on announcements of opportunity. The launch will be streamed live in Japanese and English via JAXA's YouTube channel, with an ESA image release confirming a successful launch to follow on October 20.