Japan has launched a spacecraft on an ambitious mission to collect dust from Phobos, one of Mars’ two moons, and return it to Earth for scientific analysis.
If successful, the mission would mark the first time scientists have brought back samples from Mars or either of its moons for study in laboratories on Earth.
The Mars Moons Exploration (MMX) mission, led by the Japan Aerospace Exploration Agency (JAXA), is scheduled to reach Phobos in August 2027. The spacecraft is expected to return its samples to Earth in 2031.
Scientists hope the mission will finally solve the long-standing mystery of how Mars’ moons formed.
“There hasn’t yet been a successful mission to go to Phobos and bring a bit back to Earth,” said Professor Sara Russell from the Natural History Museum in London, who serves as the mission’s deputy for sample analysis.
“I think this is an incredibly ambitious and fun mission,” she added.
There are only three moons in the inner Solar System: Earth’s Moon and Mars’ two moons, Phobos and Deimos. Both Martian moons are small and irregularly shaped, resembling space rocks or potatoes.
Phobos measures about 20km across, while Deimos is approximately 10km wide.
As the spacecraft approaches Mars, it will study Deimos before focusing on Phobos. The mission also plans to deploy a small rover to explore the moon’s surface and identify a suitable landing site for the main spacecraft.
Landing on Phobos presents a significant challenge because the moon has very weak gravity, while Mars’ much stronger gravitational pull complicates the process.
Professor Russell said no rover had ever landed on a moon as small as Phobos.
Once the landing site has been selected, the spacecraft will touch down and use a robotic arm and two sampling devices to collect dust and other surface material.
The samples will be sealed inside a capsule and returned to Earth, with the spacecraft expected to deliver them to the Woomera desert in South Australia in 2031.
Only about 10g of material is expected to be collected, but scientists believe that will be enough for extensive research.
Dr Chrysa Avdellidou from the University of Leicester, who is working with the Japanese mission, said even individual grains could provide valuable scientific information.
“You don’t need to have kilos back from a surface in order to do science. So it’s worth every gram,” she said.
One of the mission’s main objectives is to determine how Phobos and Deimos formed around 4.5 billion years ago.
Scientists are currently considering two leading theories. The first suggests that a large space rock struck Mars early in its history, scattering debris that eventually formed the two moons.
The second proposes that Phobos and Deimos were asteroids from the outer Solar System that were captured by Mars’ gravitational pull.
Professor Russell said analysing the samples’ chemical and mineral compositions should help scientists distinguish between the two possibilities.
The team also hopes the samples could contain tiny fragments of Mars itself.
Because Phobos orbits relatively close to the planet, material blasted off Mars during asteroid impacts may have travelled into space and become embedded in the moon’s surface.
“If the sample we get back contains grains of Mars as well, it can give us really direct information about the composition and history of Mars,” Russell said.
The mission comes as scientists continue to pursue the long-standing goal of bringing pristine Martian material back to Earth.
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 mission, which was intended to retrieve those samples, has effectively been cancelled after funding was halted by the US Congress.
China is also planning a Mars sampling mission, scheduled for launch in 2028, with the aim of returning material to Earth in 2031.
Fragments of Mars have already reached Earth naturally in the form of meteorites blasted off the planet’s surface by asteroid impacts. However, these rocks can become contaminated by Earth’s atmosphere, dust, soil and water after landing.
Scientists therefore hope that samples collected directly from Mars or its moons will provide a much cleaner record of the Solar System’s history.
By analysing material from Phobos, researchers could gain crucial insights into the origins of Mars’ moons and potentially uncover new evidence about the Red Planet itself.
