Japan will launch its unmanned Martian Moons Exploration probe on October 20, 2026, on a flagship H3 rocket from Tanegashima Space Center. The historic mission aims to collect at least 10 grams of material from Phobos to uncover how Mars and its moons formed.
The Launch Window and Rocket Configuration
The Japan Aerospace Exploration Agency announced that the Martian Moons Exploration mission will lift off at 4:41 a.m. local time on October 20 from Tanegashima Space Center on a small island in southwestern Japan. The spacecraft will ride aboard H3 rocket No. 10, utilizing the booster’s most powerful configuration to achieve the necessary escape velocity for deep-space travel.
The flight was originally scheduled for 2024 but faced a mandatory delay following the failed maiden flight of H3 rocket No. 1 in 2023. With the propulsion system now cleared, the spacecraft stands approximately 5.3 meters tall and spans about 9 meters with its solar panels fully deployed.
Journey to Phobos and Surface Operations
Weighing 4,480 kilograms at launch, the spacecraft is built with three distinct modules engineered for the interplanetary transit, the exploration of Phobos, and the eventual return trip to Earth. After a voyage lasting roughly one year, the probe will enter orbit around Mars and conduct extensive observations before beginning its descent sequence.
The primary destination is Phobos, the larger of Mars’s two natural satellites. Phobos orbits approximately 6,000 kilometers above the Martian surface and measures between 20 and 30 kilometers across. A rover jointly developed by French and German teams will touch down on the moon first to conduct surface observations. Following the rover deployment, the main spacecraft will attempt two landings of its own to gather samples.
International Collaboration and Scientific Stakes
The mission brings together space agencies from the United States and Europe, alongside France’s National Centre for Space Studies and the German Aerospace Center, supported by a score of universities and technology companies. While the probe will focus its sampling efforts on Phobos, it will also perform observations of Deimos, the second Martian moon, without landing on it.
Researchers hope the returned materials will finally settle a longstanding debate regarding the origin of the Martian moons.
The sources do not provide a quote from Patrick Michel regarding a hypothesis that the moons are captured asteroids from the outer Solar System.
Sample Return and the 2031 Timeline
The probe will collect at least 10 grams of sand, rock, and surface material from Phobos. These specimens will be sealed securely inside a dedicated return capsule before the spacecraft begins its long trek back toward Earth.
If the mission proceeds according to its timeline, the return capsule will detach and parachute down for retrieval in Australia in fiscal 2031.
Laying Groundwork for Crewed Mars Missions
Beyond answering questions about planetary origins, the mission serves a vital logistical purpose for future human spaceflight. By demonstrating the technologies required for an uncrewed round trip to the Martian system, the project evaluates whether Phobos can serve a practical operational role in future exploration.
JAXA has emphasized that the data gathered will explore the possibility of using Phobos as a natural space station. Establishing round-trip capabilities to the Martian system is viewed by international space agencies as an essential step for crewed Mars exploration in the decades ahead.
