Japan launches MMX probe to Mars moon Phobos, aiming to return samples in 2031

Launch from Tanegashima

The H3 rocket, in its most powerful version with two main engines and four boosters, lifted off at 4:41 a.m. Japan time on Tuesday, 20 October, from the Tanegashima Space Center in southwestern Japan. About an hour later the Japan Aerospace Exploration Agency (JAXA) confirmed that the probe had separated from the rocket and entered its planned orbit, and the first signals showed normal operation. Jiji Press reported that the placement in orbit came about 1 hour and 11 minutes after liftoff. The spacecraft weighs 4,480 kilograms and stands about 5.3 meters tall. The launch was originally planned for 2024 but was postponed after the failed first flight of the H3 rocket. The launch window reportedly runs until 7 November, according to the German Aerospace Center (DLR).

Reactions and political backing

H3 project manager Makoto Arita said the launch had been carried out with exceptional precision. Prime Minister Sanae Takaichi congratulated the team on X and expressed hope that the mission would succeed. JAXA president Hiroshi Yamakawa told a press conference that the probe had taken the first step toward an exploration mission in the Martian sphere and pledged to do everything possible to keep it working. Takaichi also said her administration has designated the space sector a strategic field of the economy, and promised to expand launch frequency and overall reliability.

Goals and partners

JAXA leads the mission in cooperation with NASA, France's CNES, Germany's DLR and the European Space Agency (ESA). The probe is meant to settle how Mars's two moons formed, with researchers weighing two explanations: a giant impact or the capture of asteroids. Sources also say the mission should yield insights into the origins of Mars and its moons, as well as the origin of life on Earth. The probe will additionally study whether Phobos could serve as a natural space station for trips between Earth and Mars. The mission would be the first to return samples from a Martian moon and the first round-trip voyage to the Martian system.

Cruise, landing and sampling

After about a year in transit, the probe is due to reach Mars in August 2027, first entering orbit around the planet before closing in on Phobos. Once there, it will map the moon's surface to identify two candidate landing sites. Before sampling, the IDEFIX rover, a 25-kilogram vehicle developed by France and Germany, is to be released from about 40 meters above the surface and will become the first vehicle to drive on Phobos. The main probe is then to land twice and collect at least 10 grams of material, and it will also observe Deimos. Reports differ on timing: Jiji Press says both landings are planned for 2029, while a schedule attributed to ESA in Berliner Zeitung puts the rover release in early 2029 and the sampling in 2030.

Return to Earth

The probe is due to leave the Martian system in November 2030 and release a capsule carrying the samples. That capsule is expected to reach Earth in July 2031 and land in a desert region of Australia, after which Berliner Zeitung reports it would be taken to Japan. ESA says part of the material would be made available to European scientists.

JAXA is applying planetary protection principles, and the MMX and its assembly site have undergone microbial surveys, with a microbial testing facility set up at Tanegashima. Concerns exist that returned samples could carry microbes from Mars, because meteorite impacts may have sent sand from the Martian surface to Phobos. The mission lifetime is described as five years in total, according to LaSexta.