On October 20, 2026, at 4:41 a.m. local time, the Japan Aerospace Exploration Agency successfully launched its flagship H3 rocket carrying the unmanned Martian Moons eXploration probe from the Tanegashima Space Center, beginning a journey to retrieve physical samples from Mars’s inner moon, Phobos, and return them to Earth.
Resolving the Origin of the Martian Moons
Despite decades of telescopic observation and orbital reconnaissance, Mars’s inner moon Phobos remains one of the least understood bodies in the inner Solar System. The formation of Phobos remains a subject of active scientific debate. Should Phobos turn out to be a captured asteroid, scientists would anticipate discovering minerals analogous to those found in carbonaceous chondrites, which are abundant in carbon alongside water-bearing or water-altered minerals.
Direct analysis of physical samples returned to Earth will help researchers understand exactly what the moon is made of in a way that remote sensing alone cannot achieve. If Phobos is a captured asteroid, scientists expect to find minerals like those present in carbonaceous chondrites, which are rich in carbon and minerals modified by water.
Phobos as a Composite Archive of Martian History
Phobos maintains an exceptionally low orbital altitude of approximately 6,000 kilometers above Mars’s surface. This close proximity means surface material blasted into space by asteroid impacts can reach Phobos, incorporating into the loose dust and fragments covering the moon’s surface. As a result, the specimens gathered from Phobos could hold a combined archive detailing the progression of the Martian crust and its prehistoric weather patterns.
Given that ancient Mars featured warmer and wetter conditions, any past Martian life could have had its remnants or metabolic derivatives blasted into the cosmos by collisions, with a portion of that debris potentially settling on Phobos. Kiyoshi Kuramoto, a planetary scientist at Hokkaido University in Japan and a member of the mission team, told Science that there is a possibility that chemical traces of biological activity might be contained within that sand sample.
Engineering the Low-Gravity Sample Return
Phobos has a diameter of 14 miles, creating an object with a very small gravitational pull and a low escape velocity. Executing a sample-return operation from such a low-gravity body presents considerable engineering complexity.
The spacecraft is scheduled to arrive in the Martian system in August 2027. Upon arrival, high-resolution imaging will provide surface characterisation of Phobos. The payload features spectrometers for orbital mineral mapping alongside a roving vehicle to evaluate landing spots, backed by collaborative efforts from NASA, the European Space Agency, Germany, France, and Australia.
French-German Rover Will Scout Phobos for Safe Landing
Named IDEFIX, this Franco-German robotic explorer will pioneer surface navigation on Phobos, gathering environmental data to guarantee a secure touchdown. Once the probe arrives at the moon, it will land twice in separate locations to collect samples. One device will collect ground surface samples by acting like a vacuum cleaner, while another will drill into the surface.
The Japanese space agency pointed out that the project will also investigate Phobos’s potential to serve as an interim orbital outpost by outlining the logistical parameters for a round-trip journey, a vital prerequisite for crewed expeditions to Mars. Nicky Fox, associate administrator of NASA’s Science Mission Directorate, stated in a message of encouragement broadcast on the JAXA live stream that the samples from the expedition will bring forth paradigm-shifting science on the Mars system for generations to come, especially as NASA prepares to send the first humans to Mars.
Physical samples are predicted to arrive back on Earth approximately five years from the mission launch, around 2031. These materials will undergo laboratory analysis using contemporary geochemical and isotopic techniques, with results expected to inform planetary science, astrobiology, and Solar System formation research.
