Mission to travel to
Mars and survey the red planet’s two moons; Phobos and Deimos.
The spacecraft will explore both moons and collect a sample
from Phobos to bring back to Earth.

What’s MMX?

The Martian Moons eXploration (MMX) mission is a project to explore the two moons of Mars, with a planned launch in the mid-2020s. Approximately one year after leaving Earth, the spacecraft will arrive in Martian space and enter into an orbit around Mars. It will then move into a Quasi Satellite Orbit (QSO) around the Martian moon, Phobos, to collect scientific data and gather a sample from the moon’s surface. After observation and sample collection, the spacecraft will return to Earth carrying the material gathered from Phobos. The current schedule has a launch date in JFY 2026, followed by Martian orbit insertion in JFY 2027 and the spacecraft will return to Earth in JFY 2031.

Exploration of the Martian moons will help improve technology for future planet and satellite exploration. For example, advancement in the technology required to make round-trips between the Earth and Mars, the advanced sampling techniques that will be employed on the Martian moon surface and in the optimal communication technology using the Deep Space Network ground stations.

A major scientific goal for the mission is clarifying the origin of the two Martian moons and the evolution process of the Martian Sphere (Mars, Phobos and Deimos). The creation of this system is one of the keys to solving the mysteries of planetary formation in the Solar System.


Objectives of the MMX mission:

  • To investigate whether the Martian moons are captured asteroids or fragments that coalesced after a giant impact with Mars, and to acquire new knowledge on the formation process of Mars and the terrestrial planets.
  • To clarify the mechanisms controlling the surface evolution of the Martian moons and Mars, and to gain new insights into the history of the Mars Sphere, including that of the Martian moons.

"Understanding the origin and evolution of the planets that leads to the start of life” is one of today’s key scientific goals. As Mars is thought to have once had a surface environment similar to the Earth with the potential for life, the planet is one of the most important exploration targets.

The Martian moons are expected to have accumulated sediment that was been ejected from Mars over billions of years. Observing the moons will therefore provide information on the evolution of the Martian surface. Moreover, if the moons were formed during a collision between Mars and gigantic asteroids, the moon material will reveal the original conditions on Mars during this early time, offering insights into the planet’s formation and its young environment. Alternatively, if the moons are captured asteroids, their composition will help clarify the transport process of volatile components (such as water) needed for habitability.

In other words, exploring the Martian moons is important for not only understanding the moons themselves, but also for future planetary science.


To achieve the purpose of the MMX mission, the spacecraft needs to achieve various requirements. After separating from the launch rocket, the spacecraft must satisfy:

  • Important requirements to maintain the spacecraft funcationality, such as electric power, heat, and communication with the Earth.
  • Requirements from the science instruments, such as altitude and timing of scientific observations.

In-depth studies are being conducted to design a spacecraft that meets these requirements.


In addition to collecting samples, MMX will also perform remote sensing of Mars and its moons using a suite of observational instruments. It is still not clear how the two small Martian moons were formed and what processes they have undergone. The surface of Phobos seen in visible and near infrared light is not uniform, suggesting the possibility of different constituent materials. Discussions are being held with both Japanese and international scientists to determine where samples should be collected. Observational data obtained by the remote sensing instruments onboard MMX will be used to determine the sampling locations.


In the MMX project, the spacecraft system and science teams collaborate in working groups aimed at solving numerous difficult and challenging tasks.

Landing Operation Working Team

LOWT is a team consisting of system and science experts who conduct research studies related to the Martian moons landing operation.

Mission Operation Working Team

MOWT and the Mission Operation Preparation Working Team (MOPWT) study science measurement operation planning and feasibility.

Data Processing Working Team

DPWT studies issues relating to the ground data processing of mission data sent from the spacecraft.

Rover Operation Working Team

ROWT conducts studies related to the operation of the on-board MMX rover that will explore Phobos.

Landing Site SelectionWorking Team

LSSWT discusses considerations related to the selection of landing sites on Phobos.

Sample Analysis Working Team

SAWT members research topics related to the analysis of the sample MMX will return from Phobos.