Japan is about to try something no space agency has done: land on Mars's moon Phobos, scoop up a sample, and bring it home. The Martian Moons eXploration mission, MMX, is scheduled to lift off on an H3 rocket from Tanegashima at 04:41 JST on 20 October 2026 (19:41 UTC on 19 October).
Status as of October 15, 2026: MMX has not launched yet. Launch dates can slip with weather or technical checks, so confirm the time on JAXA's live stream before you stay up for it. We will update this post once the spacecraft is on its way.
The short version
- What: a JAXA-led mission to Mars's two moons, Phobos and Deimos, with the first sample return from Phobos.
- Launch: H3 rocket from Tanegashima Space Center, 04:41 JST on 20 October 2026.
- Arrival: Mars orbit about a year later (August 2027), then into orbit around Phobos from September 2027.
- Landing and sampling: 2030, at least 10 grams of material.
- Home: a sample return capsule lands in Australia in 2031 and is taken to JAXA in Japan.
- Partners: NASA, CNES (France), DLR (Germany), and ESA.
Why Phobos?
Phobos and Deimos are small, dark, oddly shaped moons, and nobody knows where they came from. Two ideas compete:
- Captured asteroids. If so, the moons should hold a lot of water and organic material, preserved from the early Solar System.
- Debris from a giant impact on Mars. If so, the heat of that event would have driven off most water, and the moons would be a record of Mars's own violent youth.
A sample from the surface can tell the two stories apart. Phobos's surface is also likely mixed with material thrown off Mars over billions of years, so MMX may bring back a little of Mars itself, without ever landing on the planet. The answers feed into a bigger question: how rocky planets, including ones around other stars, form and evolve, and what conditions on Mars may once have suited life.
How the spacecraft is built
MMX weighs about 4,200 kg including fuel and is made of three modules stacked together:
- Propulsion module: chemical propulsion for the trip to Mars, braking into orbit, and guidance and control. It is dropped once its job is done.
- Exploration module: the lander. Four legs, two sampling systems, and the science instruments, plus the Idefix rover that it deploys before landing.
- Return module: the part that comes home. It has the high-gain antenna, two solar wings, the main engine for leaving Mars, and the roughly 60 cm sample return capsule with its heat shield.
Two ways to grab a sample
Phobos's gravity is tiny, so landing and digging are nothing like Apollo or Hayabusa2. MMX carries two samplers as a hedge:
- C-SMP (corer): a robotic-arm corer that drills a small core out of the surface.
- P-SMP (pneumatic): a puff of pressurized gas kicks surface grains up a tube into a collection container. It descends from the PlanetVac technology developed by Honeybee Robotics with support from The Planetary Society.
The target is at least 10 grams, enough for a long list of labs to study for decades.
Idefix: a 25 kg rover that weighs 15 grams
Idefix is a small rover built jointly by Germany's DLR and France's CNES, derived from the MASCOT lander that rode on Hayabusa2. On Earth it has a mass of 25 kg. On Phobos, with almost no gravity, it would weigh about as much as 15 grams does here.
It is released in early 2029, ahead of the main landing. It scouts the surface, helps the team choose a safe landing spot, and measures the composition and texture of the ground with its radiometer, Raman spectrometer, and cameras.
A quasi-satellite orbit
MMX will be the first spacecraft to fly a quasi-satellite orbit around Phobos. Phobos is so small that a normal orbit around it would be unstable under Mars's much stronger pull. Instead, MMX stays in orbit around Mars, tuned so that from Phobos's point of view it appears to loop around the moon. It is a cheap, stable way to hover close to a tiny world.
What it carries
The mission has 11 science instruments, seven on the main spacecraft and four on the rover. Highlights:
- MEGANE: gamma-ray and neutron spectrometer for the chemical makeup of the surface (NASA).
- MIRS: near-infrared spectrometer (CNES and French labs).
- OROCHI, TENGOO, and a LIDAR: cameras and laser ranging for 3D maps of both moons.
- IREM, MSA, and CMDM: radiation, ion, and dust monitors.
- Two Super Hi-Vision cameras (4K and 8K): from NHK, so the public can see Phobos in high resolution.
On the way back, MMX will also make several close passes of Deimos, mapping the second moon before it leaves the Martian system. ESA's Mars Express is expected to remain operating and may support observations, and ESA provides deep-space communications equipment and tracking through its ground stations.
The timeline
| 20 Oct 2026 | Launch on H3 from Tanegashima |
| Aug 2027 | Enters Mars orbit |
| Sep 2027 | Begins orbiting Phobos (quasi-satellite orbit) |
| Early 2029 | Idefix rover released |
| 2030 | Landing on Phobos and sample collection; departs Mars |
| 2031 | Sample capsule lands in Australia; samples go to Japan |
From Hayabusa to MMX
MMX continues a line that Spaceship Adventures keeps coming back to. The original Hayabusa returned the first samples from an asteroid in 2010 after a seven-year ordeal. Hayabusa2 brought back material from Ryugu in 2020. MMX takes the same craft of low-gravity touchdown and sample return to a moon of another planet, with Idefix inheriting its design from MASCOT.
That heritage is the whole idea behind the Yamabiko, the JAXA Heritage Ship in Hoshi no Isan, where each compartment honors a real mission. You can meet the missions already aboard on the JAXA missions page. MMX is the kind of mission we would want a place for when it lands its sample.
Want to learn more?
Our free Space Studies course covers the background: launch vehicles and spacecraft, non-U.S. space programs, and planetary protection, which matters for any sample-return mission.
How to watch
JAXA will stream the launch live on YouTube in Japanese and English, and ESA will publish an image release confirming liftoff on 20 October.
Sources
- ESA: Mars moon lander set to launch on 19 October
- ESA: MMX factsheet
- The Planetary Society: MMX, Japan's Martian Moons eXploration mission
- Wikipedia: Martian Moons eXploration