NASA is contributing to Japan’s Martian Moons eXploration (MMX) mission, an ambitious planetary science project designed to investigate Phobos and Deimos, the two small moons orbiting Mars.

The mission, led by the Japan Aerospace Exploration Agency (JAXA), aims to improve scientific understanding of how these moons formed and how their history is connected to the evolution of Mars and the early Solar System.

By combining spacecraft observations with plans to collect and return a sample from Phobos, MMX could provide scientists with valuable evidence about the origins of these unusual celestial bodies.

Why Mars’ Moons Interest Scientists

Phobos and Deimos are much smaller than Earth’s Moon and have irregular shapes that resemble asteroids more than large planetary satellites.

Their origins remain uncertain. One possibility is that they are captured asteroids that were drawn into orbit around Mars. Another explanation suggests that they formed from material ejected during a major impact on the planet.

Distinguishing between these possibilities requires detailed information about the moons’ composition, internal structure and geological history.

MMX is designed to collect observations that could help researchers determine which explanation is more consistent with the available evidence.

Japan Leads an International Exploration Effort

JAXA is responsible for the overall mission, while international partners contribute scientific instruments, technical expertise and other forms of support.

NASA’s participation reflects the importance of cooperation in complex planetary exploration projects. Missions to distant worlds require advanced spacecraft engineering, precise navigation and specialised scientific equipment.

Collaboration also allows researchers to combine different instruments and expertise, increasing the scientific value of the observations collected.

International partnerships can help expand the range of investigations possible within the constraints of a single spacecraft mission.

A Sample From Phobos Could Reveal Its History

One of MMX’s principal objectives is to collect material from Phobos and return it to Earth for detailed laboratory analysis.

Laboratories on Earth can conduct measurements that may be difficult or impossible to perform fully with instruments carried aboard a spacecraft.

Researchers could examine the sample’s chemical composition, mineral structure and other properties to investigate how the moon formed.

If the material contains clues about ancient impacts or the early Solar System, it could also contribute to a broader understanding of planetary formation.

Sample-return missions are technically challenging because they require spacecraft to reach a target, collect material, preserve it and transport it safely back to Earth.

Exploring Deimos and the Martian Environment

Although Phobos is the main target for sample collection, the mission also plans to study Deimos and the broader environment around Mars.

Observations of both moons could help scientists compare their surfaces and determine whether their properties support a common origin.

Understanding the moons may also provide insight into Mars itself, including the history of impacts and the processes that shaped the planet’s surroundings.

The mission’s findings could complement data collected by Mars orbiters, landers and rovers operating as part of other exploration programmes.

Challenges of Operating Near Small Moons

Phobos and Deimos have extremely weak gravitational fields compared with Earth. Their irregular shapes and limited gravity make close-range navigation and landing operations technically demanding.

A spacecraft must carefully manage its position and movement to approach the surface and carry out sampling activities.

Engineers also need to protect the spacecraft’s scientific instruments and ensure that collected material can be stored securely for the return journey.

These challenges make MMX an important test of technologies that could support future missions to small planetary bodies.

Why the Mission Matters for Planetary Science

Studying Mars’ moons could help researchers understand how planetary systems evolve and how small bodies move and change over billions of years.

The results may also improve scientific knowledge of asteroids, impact processes and the distribution of material throughout the Solar System.

By returning samples to Earth, MMX could allow scientists to investigate questions that remote observations alone cannot conclusively answer.

The Road Ahead

The MMX mission represents a major international effort to investigate two of the Solar System’s least-understood planetary moons.

Its combination of remote observations, close-range exploration and sample-return objectives could provide new evidence about the formation of Phobos and Deimos.

As Japan and its international partners advance the mission, researchers will be looking for discoveries that deepen our understanding of Mars and the early history of the Solar System.