If successful, the Mars Moons Exploration (MMX) mission will achieve the first-ever return of samples from Mars or either of its moons. Scientists hope the findings will help explain how the moons formed and provide new insights into the Red Planet’s history.
Led by the Japan Aerospace Exploration Agency (JAXA), the spacecraft is expected to reach Phobos in August 2027. It will first study Mars’ other moon, Deimos, before focusing on Phobos.
Prof Sara Russell of the Natural History Museum, who is deputy for sample analysis on the mission, described it as an ambitious project, noting that no previous mission had successfully collected material from Phobos and returned it to Earth.
Exploring Mars’ mysterious moons
Mars has two small, irregularly shaped moons, Phobos and Deimos. Phobos measures about 20 kilometres across, while Deimos is approximately 10 kilometres wide.
The MMX spacecraft plans to deploy a small rover to explore Phobos and identify a suitable landing site. The task is expected to be challenging because the moon has very weak gravity and is close to Mars, whose much stronger gravitational pull complicates landing operations.
After the rover surveys the terrain, the spacecraft will attempt to land on Phobos and use a robotic arm and two sampling devices to collect dust from its surface.
The collected material will be sealed in a capsule and returned to Earth in 2031. The capsule is scheduled to land in South Australia’s Woomera region.
Scientists expect the mission to bring back around 10 grams of material.
Dr Chrysa Avdellidou of the University of Leicester, who is working with the Japanese mission, said even such a small quantity could support several scientific studies.
Researchers can examine individual grains to investigate their chemical composition and mineral structure, meaning large quantities of material are not necessary to produce valuable scientific findings.
How did Mars’ moons form?
Scientists have two leading theories about the origins of Phobos and Deimos.
One suggests that a large space rock struck Mars early in the planet’s history, scattering debris that eventually formed the two moons.
The other proposes that the moons are asteroids originating elsewhere in the Solar System that were captured by Mars’ gravitational pull.
Russell said laboratory analysis of the returned samples should help distinguish between the two explanations by revealing the material’s chemistry and mineral composition.
The samples could also provide an unexpected discovery. Because Phobos orbits close to Mars, impacts on the planet may have blasted fragments of Martian material onto the moon’s surface.
If those fragments are present in the collected dust, scientists could gain direct evidence about Mars’ composition and geological history.
Race to bring Mars samples to Earth
Scientists have long sought to bring samples directly from Mars to Earth, where laboratories can conduct detailed analyses that are difficult to perform using robotic instruments on the planet.
NASA’s Perseverance rover, which has been exploring Mars since 2021, has collected and stored samples in sealed containers. However, the planned NASA-European Space Agency Mars Sample Return programme, which was intended to retrieve those containers, was effectively cancelled after its funding was halted by the US Congress.
China is also planning a Mars sample-return mission, with a launch scheduled for 2028 and the return of material targeted for 2031.
Fragments of Mars have already reached Earth naturally as meteorites. These rocks were blasted off the planet by asteroid impacts before travelling through space and eventually landing on Earth.
However, Martian meteorites are rare and can become contaminated by Earth’s atmosphere, soil, water and dust after arrival.
Scientists hope the MMX mission will provide a carefully collected sample that offers a more direct opportunity to study the composition and origins of Mars’ moons.
