Japan to Launch MMX Spacecraft to Bring Back the First Samples From Mars’s Moon Phobos

Illustrative image.

Last updated: October 18, 2026. The launch has not happened yet, and this article will be updated after liftoff.

TOKYO — Japan is preparing to launch a spacecraft toward Phobos, one of the two small moons of Mars, on a mission that aims to bring back the first samples ever collected from a moon other than Earth’s. The Japan Aerospace Exploration Agency (JAXA) plans to lift off its Martian Moons eXploration mission, known as MMX, on an H3 rocket from the Tanegashima Space Center at 04:41 Japan time on October 20, 2026, which is 19:41 UTC on October 19, and the spacecraft is expected to return its samples to Earth in 2031.

Key Takeaways

• MMX is set to launch on an H3 rocket at 04:41 JST on Oct. 20, 2026, with a launch window that runs through November.
• It would be the first mission to land on Phobos and bring back at least 10 grams of material from the Mars system.
• A French-German rover named Idefix will scout the surface before the main spacecraft lands.
• The sample capsule is planned to land in Australia in 2031.

What Is the MMX Mission?

MMX is a sample return mission led by JAXA, with NASA, the French space agency CNES, the German Aerospace Center (DLR) and the European Space Agency contributing. The spacecraft will study both of Mars’s moons, Phobos and Deimos, but its main goal is to land on Phobos, the larger and closer of the two, collect soil, and carry it home. According to ESA, it will be the first mission to land on Phobos and the first to return a sample from the Mars system to Earth, and NASA is contributing an instrument called MEGANE that will take a chemical inventory of Phobos from orbit.

The Journey to Phobos and Back

After launch, MMX should arrive at Mars in August 2027, about a year later, and a month after that it will slip into what is called a quasi-satellite orbit. From there the spacecraft will appear to circle Phobos, although it is actually orbiting Mars and tracking along with the motion of the moon. It will spend about three years studying Phobos from a distance before descending to collect material, and Phobos has so little gravity that the 25-kilogram Idefix rover will weigh only about as much as 15 grams would on Earth. After collecting its samples, the spacecraft will lift off, pass Deimos several times while leaving Mars in 2030, and send its return capsule to Earth in 2031.

How MMX Will Collect Its Samples

The spacecraft is made up of three modules: a propulsion module that carries it to Mars, an exploration module that lands on Phobos and collects the samples, and a return module that brings them back to Earth. The exploration module has four landing legs and two different sampling systems. One is a corer that collects material from about two centimeters below the surface, and the other is a pneumatic sampler that uses pressurized gas to lift loose material from the surface into a sample container. Together they are designed to gather at least 10 grams of Phobos material, about 0.35 ounces, which will be sealed in the return capsule for the trip home.

Meet Idefix, the Rover Heading to Phobos

Before the main spacecraft lands, MMX will release a small rover named Idefix, built jointly by CNES, DLR and JAXA and named after the dog in the French comic series Asterix. The rover weighs about 25 kilograms on Earth, and it is expected to be the first rover to attempt wheeled travel on a low-gravity surface. It is planned to be dropped from an altitude of about 40 to 100 meters in early 2029 and to operate for roughly 100 days, studying the soil and helping the team decide where the main spacecraft should touch down. Its measurements are also meant to reduce the risks of the sampling attempt, which is expected to take place in the spring or summer of 2029.

Why Phobos, and What Scientists Hope to Learn

Scientists chose Phobos mainly because it sits closer to Mars than Deimos and may therefore hold more information about the planet, and JAXA officials say material from Mars itself is expected to make up about 0.1% of what is collected from the surface. The deeper question is where the two moons came from. One idea is that they formed from debris thrown into orbit by a giant impact on Mars, and another is that they are asteroids that Mars captured billions of years ago. MMX carries around a dozen instruments to help answer this, including an infrared spectrometer called MIRS to study the moon’s minerals and NASA’s MEGANE instrument, which uses gamma rays and neutrons to measure its chemical makeup. Project manager Yasuhiro Kawakatsu has also said the samples could help scientists judge whether a Martian moon might one day serve as a base for human missions to the planet.

A Mission With a Long Road to Launch

JAXA originally planned to launch MMX in 2024 but stood down because of problems with the H3 rocket, and because Mars and Earth line up properly for interplanetary launches only about once every 26 months, the delay was significant. The stakes are high, since Russia attempted a Phobos sample return with its Fobos-Grunt mission in 2011, but that spacecraft never left Earth orbit. If MMX succeeds, Japan would become the first country to return material from the Mars system, building on its earlier asteroid sample missions. Because the launch window runs through November, the date could still change if weather or technical issues cause a delay.

How to Watch the Launch

ESA says the launch will be streamed live in Japanese and English on JAXA’s YouTube channel, and it plans to issue an image release confirming a successful launch on October 20. We will update this article once the rocket has lifted off and the spacecraft’s status is confirmed.

Sources: ESA (launch announcement), ESA (MMX factsheet), Astronomy, The Planetary Society, The Conversation, Space.com and The Associated Press, as of October 18, 2026.