Japan's MMX Mission Targets Mars's Moon — A High-Stakes 2029 Landing

Japan's space agency, JAXA, is preparing to launch its Martian Moons eXploration (MMX) mission, an ambitious attempt to land on Mars's moon Phobos and return a sample to Earth. According to Ars Technica, the mission's climax will occur in 2029, when the spacecraft will attempt one or two separate landings to collect at least 10 grams of regolith. This is not just another rock-collection trip; it's a high-risk engineering challenge aimed at resolving a long-standing debate about the formation of the inner solar system.

An Audacious Timeline

The MMX mission plan is a multi-year exercise in precision. After a planned launch in 2026, the spacecraft will spend about a year traveling to the Martian system. Once in orbit around Mars, it will conduct extensive reconnaissance of both Phobos and the smaller moon, Deimos, before zeroing in on its primary target. The most critical phase begins in 2029 with the landing attempts on Phobos. Ars Technica reports the plan includes provisions for up to two attempts, an implicit acknowledgment of the difficulty and high probability of failure.

Landing on Phobos presents unique challenges compared to missions to asteroids or larger planetary bodies. Its weak and uneven gravity makes a traditional landing impossible. The MMX spacecraft will have to perform a slow, controlled descent and essentially dock with the surface for a few hours to collect its sample before ascending. After securing the sample, the craft will depart the Martian system for its return journey, with the sample capsule scheduled to arrive back on Earth in 2031.

Solving a Planetary Mystery

The scientific payoff for this complex operation could be immense. As detailed by Wired, the central goal is to determine the origin of Phobos. Two competing theories exist: either Phobos is a captured asteroid, drawn into Mars's orbit from the asteroid belt, or it is a remnant of a catastrophic impact on Mars itself, blasted into orbit billions of years ago. The composition of the returned soil sample should provide a definitive answer.

If Phobos is a captured asteroid, its material would offer a pristine look at the building blocks of the early solar system from a region different than other sampled asteroids. If it's a piece of Mars, the sample would give scientists access to ancient Martian surface material without the cost and complexity of a full Mars surface sample-return mission. Both sources agree that either outcome would provide invaluable data for planetary scientists. This mission follows JAXA's previous successes with the Hayabusa and Hayabusa2 missions, which returned samples from near-Earth asteroids, but MMX elevates the difficulty by operating in the deep gravity well of Mars, nearly 1,000 times farther from Earth than the Moon.