Japan's MMX heads for Phobos to bring a sample home

Update (20 October 2026): MMX launched successfully at 04:41 JST on 20 October and separated on its planned trajectory. Read our launch report.

Japan is about to try something no space agency has done: fly to Mars, land on one of its moons, and come home with a sample. JAXA's Martian Moons eXploration (MMX) mission is scheduled to launch on an H3 rocket from the Yoshinobu Launch Complex at the Tanegashima Space Center at 04:41 JST on 20 October 2026, according to JAXA and the European Space Agency. In Europe that is still the evening of 19 October: 21:41 in Paris and 22:41 in Kyiv. Japan's public broadcaster NHK confirmed on 16 October that the launch was still on for the morning of the 20th.

JAXA has reserved a backup window from 21 October to 7 November in case the date slips. You can watch live, in Japanese and English, on JAXA's YouTube channel.

Why Phobos?

Mars has two small moons, Phobos and Deimos, and scientists still don't know where they came from. One idea is that they are captured asteroids. Another is that they formed from debris thrown into orbit when something huge hit Mars. Flybys have only given brief glimpses, and ESA says the best way to settle the question is to bring material back to labs on Earth.

"The data and samples returned by MMX are a window to study the evolution of Mars and the Solar System," says Elliot Sefton-Nash, ESA's MMX project scientist.

Several firsts at once

• First spacecraft to orbit Phobos, using what ESA calls a "quasi-satellite orbit".
• First samples from a moon other than ours. The spacecraft has special equipment to land and collect material in Phobos's extremely weak gravity.
• First round trip to the Mars system. ESA notes that this kind of return flight matters for future missions that hope to bring back samples from Mars itself.

What's on board

MMX carries 11 science instruments: seven on the main spacecraft and four on a small rover called Idefix. The spacecraft also carries a radiation monitor, two high-resolution cameras and two different sampling devices. Idefix has a mass of 25 kg, but on Phobos it will weigh about as much as 15 grams would on Earth. Its jobs are to scout the surface ahead of the main landing and to study what the ground is made of.

The mission is led by JAXA with NASA, the French space agency CNES, Germany's DLR and ESA.

What happens to the samples

The capsule will come down in Australia and then go to Japan, where the sample will be extracted, catalogued and shared with partner agencies, including scientists in Europe. On the way home, MMX will also fly past Deimos and study Mars itself. ESA's long-serving Mars Express orbiter, cleared to operate until at least 2029, may support the observations, and the planned ExoMars Rosalind Franklin rover should complement MMX by digging into the Martian subsurface.

It's a busy season for robotic explorers: ESA's Juice probe just swung past Earth on its way to Jupiter, and NASA's Perseverance rover keeps setting distance records on Mars.