Japan Launches Five-Year Mission to Return First Martian-System Samples

Japan has launched the first mission designed to bring physical material from Mars or either of its moons back to Earth. The Martian Moons Exploration spacecraft lifted off before dawn on Oct. 20 local time from Tanegashima Island, and officials declared the launch successful about an hour later when the probe separated from its rocket’s upper stage as planned.

That separation starts a five-year campaign whose most difficult operations remain ahead. The Japan Aerospace Exploration Agency-led mission must reach Mars, map the small moon Phobos, deploy a low-gravity rover, choose safe landing terrain, collect at least 10 grams of material during a brief surface stay and send a return capsule to Australia in 2031.

Known as MMX, the $578 million mission combines a 5-ton spacecraft with contributions from five space agencies. Its first interplanetary leg is expected to end in late summer 2027, when the spacecraft reaches Mars and synchronizes its motion with Phobos, the larger and closer of the planet’s two moons.

A rover will scout before the spacecraft lands

Phobos is only about 14 miles, or 22 kilometers, across, and its weak gravity makes surface operations fundamentally different from driving on Mars. MMX will release Idefix, a French-German rover no larger than a microwave oven, above the moon. The 25-kilogram machine is designed to survive the descent, bounce and right itself if it initially comes to rest upside down.

That recovery capability has a firm operating boundary: Idefix cannot right itself after its solar panels deploy. Its landing sequence must therefore establish a usable orientation before the rover transitions into normal surface operations.

Once mobile, Idefix is designed to move at 1 millimeter per second and work for roughly 100 days. Speed is not the objective. The rover’s job is to inspect surface texture and composition while identifying powdery soil and rough terrain that could complicate the main spacecraft’s descent. The German Aerospace Center describes the rover’s design, testing and role in the mission on its official MMX project page.

This reconnaissance is a direct input to landing-site selection. Phobos may look solid from orbit, but the mechanical properties of its surface are not established well enough to treat touchdown as routine. A site that is scientifically attractive still has to provide terrain compatible with landing, sampling and departure.

Two hours to secure the sample

The main Phobos landing is planned for late 2028 or 2029. Once down, the spacecraft is expected to remain on the surface for about two hours while drilling and vacuuming dust, soil and rock into its return system. The mission requirement is at least 10 grams, roughly one-third of an ounce.

The short stay limits prolonged exposure to an uncertain surface while still allowing the collection hardware to work. MMX is designed around both a coring mechanism and a pneumatic sampler, giving the mission more than one way to acquire material. The spacecraft must then leave Phobos and reestablish controlled flight around Mars with the sample secured.

Orbital measurements will provide context that a small container of soil cannot supply by itself. Instruments will map Phobos and measure its elemental composition, helping researchers determine whether material collected from one location represents the wider moon. Those observations can also distinguish terrain differences that may influence where the sampling attempt is made.

Phobos may preserve two planetary histories

The returned material is intended to address a basic unresolved question: Did Phobos and Deimos form from debris thrown into orbit by an ancient collision with Mars, or are they asteroids captured by Martian gravity? Their asteroid-like appearance supports one explanation, while their nearly circular, equatorial orbits are easier to reconcile with formation near Mars.

Scientists also expect Phobos to hold small traces of Mars, deposited after impacts ejected material from the planet. Laboratory analysis on Earth could examine the samples with greater precision than spacecraft instruments can provide, potentially separating native Phobos material from Martian debris and identifying chemical signatures tied to the moon’s origin.

After its Phobos work, MMX is scheduled to conduct flybys of Deimos and depart the Martian region in 2030. The return module would then make the journey to Earth and release its sample capsule for landing in the Australian desert in 2031.

Japan enters this sequence with two successful asteroid sample-return missions behind it, but Mars has been less forgiving: the country’s previous Mars mission failed to enter orbit, while three earlier Russian attempts to explore Phobos also failed. MMX has cleared the launch pad. Its historic result now depends on a chain of low-gravity operations culminating in two hours on Phobos and a capsule landing five years from now.

By David Whitaker — Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.