Japan’s Ambitious Return to Mars Exploration
The Japanese space agency, JAXA, has confirmed the launch of its Mars mission, marking the country’s first foray into Martian exploration in 28 years. Scheduled for October 20, 2026, the Martian Moons eXploration (MMX) mission aims to land on Phobos, one of Mars’ two moons, with the ambitious goal of collecting over 10 grams of samples to return to Earth.
The journey to Mars is expected to take approximately one year, followed by around three years conducting operations in Martian orbit. The return trip to Earth will add another year to the timeline. If successful, this mission will represent a historic achievement as the first in the world to bring back samples from a Martian moon.
Scientific Goals of the MMX Mission
JAXA’s mission outlines a primary objective of investigating the origins of environments conducive to life on Earth-like planets. Additionally, the mission aims to develop technology for round-trip journeys to Mars, advanced surface sampling techniques, and enhanced communication technologies through new ground stations.
Two prevailing hypotheses exist regarding the origins of Phobos and Deimos. The “giant impact theory” suggests that they formed from debris ejected by a collision between a celestial body and Mars. In contrast, the “capture theory” posits that these moons are captured asteroids from the outer solar system. Both theories present compelling arguments, although there is currently no definitive evidence favouring one over the other.
Phobos and Deimos are dark in colour and exhibit light reflection properties akin to asteroids, which are believed to be rich in water and organic material. Their nearly circular orbits, aligned with Mars’ rotation, lend credibility to the giant impact theory. However, JAXA notes that neither theory has yet proven to be superior.
The Design and Functionality of the MMX Probe
The MMX probe is set to be launched from the Tanegashima Space Centre aboard an H3 rocket at 04:41 on October 20, 2026. With a launch mass of 4,480 kg, it comprises three modules: one for the outbound journey, another for exploration, and a third for the return trip.
Notably, more than half of the spacecraft’s mass is dedicated to the propellant required for its engines. Upon approaching Mars, the MMX will separate the propulsion module, which will be depleted, before deploying the exploration module following a flyby of Deimos. This design allows for a return to Earth using only the return module, optimising the use of propellant.
Mitsubishi Electric is responsible for designing and manufacturing the probe’s systems, while IHI Aerospace is tasked with the propulsion system. Myojo Electric, also part of the IHI Group, will manage the observational equipment, including a telephoto camera. Kawasaki Heavy Industries is leading the development of the robotic arm and the sample return capsule, whereas the Chiba Institute of Technology’s Planetary Exploration Research Centre will oversee the laser altimeter and dust monitor. NHK has collaborated with JAXA to develop an ultra-high-definition camera, with the total development cost exceeding $345 million.
Overcoming Communication and Gravitational Challenges
The mission faces a significant challenge in the form of a radio signal delay of between 4 to 20 minutes between Earth and the MMX. Consequently, the spacecraft must autonomously decide and execute all operational sequences, including descent, landing, and take-off, using its navigation and control capabilities.
While Phobos has only one-third of the Moon’s gravity, it is still approximately 50 times that of the asteroid Ryugu, which presents unique challenges for landing. The intermediate gravity complicates the use of a hovering descent method due to propellant requirements, increasing the difficulty of landing.
To address this, the probe is equipped with a high-precision autonomous navigation system. The landing process employs a two-stage system: initially comparing the crater’s topography at altitudes between 2 km and 300 m, and then again between 300 m and 10 m. The system analyses surface texture data to ensure a precise landing.
Furthermore, at altitudes of 300 m and 100 m, the system identifies elevation differences of 30 cm or more as hazardous zones, allowing for landing site adjustments or aborting the landing if necessary.
Innovative Sample Collection Techniques
For sample collection, the MMX employs a sophisticated system that combines a five-axis robotic arm with a drilling mechanism to insert a cylindrical device for gathering samples. This drill features a double-walled structure that leaves the outer cylinder embedded in the soil while extracting the inner cylinder, which then seals the sample within.
This methodology diverges from Hayabusa’s approach, which involved firing a projectile at the asteroid’s surface to capture resultant particles. Instead, MMX’s system directly contacts the surface to collect material from a depth of 2 cm or more, incorporating NASA’s pneumatic method that utilises nitrogen to gather finer particles from the outermost layer.
Extensive measures have been implemented to prevent sample contamination. The equipment used for sample collection undergoes rigorous cleaning with organic solvents and ultrapure water, and the probe is managed in a high-security clean room. Additionally, to avoid soil contamination during landing, the propulsion system is deactivated at about 10 meters altitude, allowing the probe to land in free fall.
Charting New Frontiers in Mars Exploration
In the realm of sample return missions from Mars, China is also advancing its “Tianwen-3” programme, anticipated for launch around 2028, with plans for a return to Earth by 2031. However, unlike MMX, which focuses on Phobos, Tianwen-3 aims to target Mars itself.
Currently, there are no plans in Europe or the United States to implement missions aimed at returning samples from Mars’ moons. The MMX mission stands as Japan’s first probe launch to Mars in nearly three decades, following the Nozomi mission in 1998. Through this international collaboration with NASA, the French National Centre for Space Studies (CNES), the German Aerospace Centre (DLR), and the European Space Agency (ESA), which provide instruments and operational support, Japan aspires to achieve the first successful insertion into Martian orbit.