The Japan Aerospace Exploration Agency (JAXA) launched the Martian Moons eXploration (MMX) mission on 20 October 2026 aboard H3 Launch Vehicle Flight No.10 from the Yoshinobu Launch Complex at the Tanegashima Space Center. The uncrewed spacecraft separated successfully about 71 minutes after liftoff and is now on a five year journey to Mars and back. If all goes to plan, MMX will collect at least 10 grams of material from the Mars moon Phobos and deliver it to Earth in 2031, the first sample return from the Martian system in history.
What Is the MMX Mission?
The Martian Moons eXploration (MMX) is Japan’s flagship sample return mission to the Mars system. The MMX spacecraft will survey both Mars moons, land on Phobos to collect surface material, and carry that sample back to Earth for laboratory study.
JAXA leads the MMX mission. It is Japan’s follow up to the celebrated Hayabusa and Hayabusa2 asteroid sample return missions, which brought material from asteroids Itokawa and Ryugu to Earth in 2010 and 2020. While those missions targeted small asteroids near Earth, MMX is far more ambitious. It must travel to Mars, operate for three years around Phobos in very weak gravity, and then fly back to Earth. No space agency has ever returned from the Martian system before.
The MMX spacecraft has three parts. The propulsion module provides thrust for the long cruise to Mars and back. The exploration module carries cameras and science instruments and landing legs for touching down on Phobos. The return module includes the Sample Return Capsule (SRC) that will separate near Earth and parachute down with the Phobos soil. Together they weigh about 4,000 kilograms at launch and carry 13 science instruments plus two different sampling devices.
What Is Phobos?
Phobos is the larger of the two moons of Mars. It is a dark, lumpy rock about 27 kilometres wide that orbits only 6,000 kilometres above Mars, circling the planet three times a day. Scientists believe it may be a captured asteroid or debris from an ancient impact on Mars.
The name Phobos comes from Greek mythology. Phobos means fear. Deimos means dread or panic. The American astronomer Asaph Hall discovered both moons in August 1877 from the US Naval Observatory in Washington. He named them after the two sons of Ares, the Greek god of war who is called Mars in Roman mythology. Hall found Deimos on 12 August and Phobos on 17 August 1877.
Phobos is tiny and misshapen. It measures about 27 by 22 by 18 kilometres and its gravity is so weak that a person weighing 60 kilograms on Earth would weigh only a few dozen grams there. Its surface is dark like coal and covered with dust, craters and long grooves. The largest scar is the Stickney crater, about 10 kilometres wide, almost half the width of the moon itself. Phobos is slowly spiralling toward Mars at about 1.8 metres every 100 years. Scientists expect it to crash into Mars or break apart into a ring in about 40 to 50 million years, which is why it is often called the doomed moon.
Mars Moons Phobos and Deimos at a Glance
| Feature | Phobos | Deimos |
|---|---|---|
| Meaning of name | Fear | Dread |
| Discovered | 17 August 1877 by Asaph Hall | 12 August 1877 by Asaph Hall |
| Size | About 27 by 22 by 18 km | About 15 by 12 by 11 km |
| Distance from Mars | About 6,000 km above surface | About 20,000 km above surface |
| Time for one orbit | 7 hours 39 minutes | 30 hours 18 minutes |
| Appearance | Heavily grooved, Stickney crater | Smoother, thick dust cover |
Mars has only two moons. Earth has one. Jupiter has more than 90 moons (as of October 2026). Both Martian moons are thought to be made of carbon rich rock similar to primitive asteroids. Their exact origin is still debated. One idea says they are asteroids captured by Mars gravity. Another idea says they formed from debris thrown into orbit after a giant impact on Mars. The Phobos sample will help settle this question.
How Will MMX Travel to Mars and Return to Earth?
The MMX spacecraft follows a five year flight plan that links launch, Mars arrival, long observation, sampling and return into one continuous journey.
| Phase | Period | What Happens |
|---|---|---|
| Launch | 20 October 2026 | H3 rocket lifts off from Tanegashima, spacecraft separates after 71 minutes |
| Cruise to Mars | October 2026 to August 2027 | About 10 month journey to the Martian system |
| Arrival at Mars | August 2027 | MMX enters orbit around Mars |
| Orbit around Phobos | From September 2027 | MMX enters a quasi satellite orbit that flies alongside Phobos for mapping |
| Detailed survey and landing preparation | 2027 to 2028 | Cameras, laser and spectrometers map the surface and select landing sites |
| Rover deployment and sampling | 2028 to 2030 | Idefix rover lands on Phobos, main spacecraft makes two soft landings to collect at least 10 grams |
| Deimos flybys | 2030 | MMX observes the smaller moon Deimos during flybys and studies Mars environment |
| Departure for Earth | Late 2030 | Spacecraft leaves Mars orbit for year long return cruise |
| Earth return | 2031 | Sample Return Capsule separates and lands in the Woomera Prohibited Area in Australia |
The sampling plan uses two complementary tools. The C-SMP corer will drill about 2 centimetres into the surface to collect an undisturbed core. The P-SMP pneumatic sampler will puff nitrogen gas to lift surface dust into a collection chamber. Using two methods guards against the unknown texture of Phobos soil.
For mapping, the MMX exploration module carries the TENGOO narrow angle camera, the OROCHI wide angle camera, the LIDAR laser altimeter for measuring height, and the MIRS infrared spectrometer built with French help. The MEGANE gamma ray and neutron spectrometer, built with the United States, will scan tens of centimetres below the surface to read the chemical makeup of Phobos from orbit. The Circum Martian Dust Monitor (CMDM) will study dust around Mars, and the Mass Spectrum Analyser (MSA) will study ions near the moons.
H3 Rocket and Tanegashima Space Center
The MMX spacecraft rode into space on H3 Launch Vehicle Flight No.10. H3 is Japan’s new flagship liquid fuel rocket. It replaces the older H-IIA and H-IIB rockets. It is built by Mitsubishi Heavy Industries for JAXA and is designed to be cheaper, more flexible and more reliable for satellites and deep space probes.
H3 had a difficult start. Its first test flight in March 2023 failed when the second stage engine did not ignite. After corrections, H3 returned to flight and has since carried Earth observation satellites and other payloads. The MMX launch is its first deep space mission, a strong test of its power and precision. The rocket flew exactly as planned on 20 October 2026.
The launch site was the Yoshinobu Launch Complex at the Tanegashima Space Center in Kagoshima prefecture in southern Japan. Tanegashima is Japan’s main spaceport for large rockets. It sits on a southern island facing the Pacific Ocean, which allows rockets to fly east over open water. Pad 2 at Yoshinobu is built specifically for H3. The center is operated by JAXA, which was formed in 2003 through the merger of three older space bodies and is headquartered in Chofu, Tokyo.
JAXA and International Partners Powering the Mission
JAXA leads the MMX mission and built the main spacecraft. Four other space agencies provide key hardware and expertise.
The National Aeronautics and Space Administration (NASA) of the United States provided the MEGANE instrument and the pneumatic sampling system. NASA built MEGANE through the Johns Hopkins Applied Physics Laboratory. The sampler mechanism was developed by Honeybee Robotics. NASA will also support navigation through its Deep Space Network. In return, NASA will receive about 15 percent of the returned Phobos sample for study at the Johnson Space Center in Houston.
The European Space Agency (ESA), headquartered in Paris, supplied deep space communication equipment including a transponder that helps track the spacecraft across millions of kilometres. ESA scientists will also analyse orbital data and the returned sample.
The National Centre for Space Studies (CNES) of France and the German Aerospace Center (DLR), headquartered in Cologne, jointly built the Idefix rover. CNES also helps plan the complex flight around Phobos and contributed the infrared spectrometer. DLR provided test facilities and rover technology. The partnership builds on an earlier success, when CNES and DLR supplied the small MASCOT lander that rode on Japan’s Hayabusa2 mission to asteroid Ryugu.
What Will the Idefix Rover Do on Phobos?
The Idefix rover is a small Franco German scout that will land on Phobos before the main spacecraft touches down. The rover weighs about 25 kilograms on Earth but would weigh only about 15 grams under the extremely weak gravity of Phobos.
Idefix is named after the small dog in the French Asterix comics, a fitting name for a tiny companion to a giant mission. It moves on wheels rather than hopping, which would make it the first wheeled vehicle to roll on such a low gravity body. It carries stereo navigation cameras, wheel cameras for close views, a RAX Raman spectrometer to identify minerals, and a miniRAD radiometer to measure surface temperature.
The rover has two jobs. First, it will photograph the surface up close and measure soil strength and temperature. This information will help JAXA choose a safe landing site for the main spacecraft. Second, it will conduct its own science for about 100 days, testing how minerals and heat behave on Phobos. Since Phobos gravity cannot hold a lander down firmly, Idefix must work quickly before it loses contact or drifts.
Why the Phobos Sample Return Matters for Planetary Science
A sample return mission brings soil back to Earth for study in laboratories. This allows far more precise tests than instruments on a spacecraft can perform. Scientists can date the grains, read their isotopes and look for organic molecules that hint at the early solar system.
Phobos sits at a crossroads. Its orbit is close to Mars, but its dark surface looks like primitive asteroids from the outer asteroid belt. If Phobos is a captured asteroid, its sample will preserve material from the birth of the planets 4.6 billion years ago. If Phobos is debris from Mars itself, its sample will reveal the history of Mars crust and the giant impact that may have created it. Either answer will clarify how Mars and its surroundings evolved.
The mission also solves practical problems for future human travel. Understanding Phobos dust, radiation levels and gravity will help planners judge whether astronauts can one day stop at Phobos before landing on Mars. The technology for a round trip to the Martian system, including autonomous landing on a tiny body and high speed re entry at Earth, has never been tested. MMX will prove it works. The capsule recovery in Australia will follow the same model JAXA used for Hayabusa2, with quick transfer of the sealed container to Japan for opening in clean laboratory conditions.
Key Takeaways
- The MMX mission was launched by JAXA on 20 October 2026 aboard H3 Flight No.10 from Tanegashima Space Center.
- MMX aims to bring at least 10 grams of soil from Phobos back to Earth in 2031, the first Martian system sample return.
- Phobos is the larger Mars moon, about 27 km wide, discovered by Asaph Hall in 1877 and named after the Greek god of fear.
- The 25 kg Idefix rover, built jointly by France’s CNES and Germany’s DLR, will scout the Phobos surface before sampling.
- NASA’s MEGANE spectrometer and ESA’s deep space communication support are key international contributions to MMX alongside CNES and DLR.
