H3-24 | Martian Moon eXplorer (MMX)

Japan's H3-24 Rocket to Propel MMX Mission to Mars' Moon Phobos

On October 31, 2026, Japan's Aerospace Exploration Agency (JAXA) will launch the Martian Moon eXplorer (MMX) mission aboard the H3-24 rocket from the Tanegashima Space Center. This ambitious endeavor aims to unlock secrets of the Martian system by targeting Phobos, one of Mars' two enigmatic moons. Unlike previous Mars missions focused on the planet's surface, MMX represents a bold step in sample-return technology, promising to bring back physical evidence from a Martian satellite for the first time.

At the heart of MMX's objectives is the collection and return of at least 10 grams of regolith from Phobos' surface. The spacecraft, weighing approximately 4,000 kilograms at launch, will orbit Mars before descending to Phobos in 2029. Equipped with advanced instruments including infrared spectrometers, neutron and gamma-ray detectors, and high-resolution cameras, MMX will analyze the moon's composition, geology, and potential water ice deposits. A key payload is the compact rover developed jointly by France's CNES and Germany's DLR, measuring just 25 centimeters across and weighing 25 kilograms. This rover will traverse Phobos' low-gravity terrain, conducting in-situ experiments on surface materials and radiation levels. The mission's sample-return capability builds on JAXA's Hayabusa2 success with asteroid Ryugu, adapting those techniques for the harsher Martian environment. By returning samples to Earth by 2031, scientists hope to determine if Phobos originated as a captured asteroid or from debris ejected during a massive impact on Mars, shedding light on the solar system's early formation.

The H3-24 rocket, developed by JAXA and Mitsubishi Heavy Industries, is a next-generation launch vehicle designed for reliability and cost-efficiency. Standing 63 meters tall with a diameter of 5.2 meters, it features a two-stage configuration powered by liquid hydrogen and oxygen. The first stage employs two LE-9 engines, each delivering 1,471 kN of thrust, augmented by four SRB-3 solid rocket boosters for enhanced lift. This setup allows the H3-24 to place up to 6.5 metric tons into geostationary transfer orbit or heavier payloads into lower orbits, making it suitable for interplanetary missions like MMX. The upper stage uses a single LE-5B-3 engine for precise orbital insertions