The Japan Aerospace Exploration Agency is scheduled to launch a spacecraft on Monday to collect and return samples from Phobos, one of the moons of Mars. The Mars Moons Exploration (MMX) mission aims to retrieve approximately 10 grams of moon dust for laboratory analysis on Earth. If successful, the mission will mark the first time material has been returned from the Martian system.
The mission addresses a scientific debate regarding the origin of Phobos and Deimos, the two moons in the inner Solar System that orbit Mars. Researchers currently hold two primary hypotheses: that the moons formed from debris created when a space rock struck Mars early in its history, or that they are asteroids from the outer Solar System captured by Mars's gravity. Prof. Sara Russell of the Natural History Museum stated that chemical and mineral analysis of the returned samples should clarify which hypothesis is correct.
The MMX spacecraft is scheduled to depart from the Tanegashima Space Center and is expected to arrive at Phobos in August 2027. Upon arrival, the craft will study the smaller moon, Deimos, before focusing on Phobos, which measures approximately 20 kilometers across. The mission includes the deployment of a small rover to scout the terrain, followed by the spacecraft landing to collect material using a robotic arm and two samplers. The collected dust will be placed in a capsule for a scheduled return to Earth in 2031, landing in the Woomera desert of South Australia.
The mission also serves as a primary alternative for obtaining Martian material following changes to other international programs. While NASA’s Perseverance rover has been collecting samples on Mars since 2021, the subsequent Mars Sample Return mission intended to retrieve them was effectively cancelled after the U.S. Congress halted its funding. Consequently, the MMX mission and a planned 2028 Chinese sampling mission represent the current active efforts to return material from the Mars vicinity by 2031. Researchers also hope the Phobos samples may contain "bonus" grains of Mars itself, ejected from the planet's surface by past asteroid impacts and landed on the moon.
The launch is set for 04:41 local time on 20 October at the Tanegashima Space Center. Following the 2027 arrival at Phobos and the subsequent surface operations, the return capsule is expected to reach Earth four years later. The mission’s success depends on navigating the complex gravitational environment created by the proximity of the small moon to the much larger mass of Mars, which Prof. Russell described as a significant challenge for landing the rover and spacecraft.