Japan's MMX is on its way to Phobos after a clean H3 launch

Japan's mission to bring home a piece of a Martian moon is off to a clean start. The Martian Moons eXploration (MMX) spacecraft lifted off on H3 flight No. 10 from the Tanegashima Space Center at 04:41:03 JST on 20 October 2026, which was 22:41 on 19 October in Kyiv. In its launch result statement, JAXA says the rocket "flew as planned", released MMX about 71 minutes and 13 seconds after liftoff and put it on its predetermined trajectory.

We previewed the mission in our MMX explainer last week. Here is what happened and what comes next.

How the launch went

According to Space.com, the H3 dropped its four solid boosters in pairs just before the two-minute mark and shed its payload fairing about a minute and a half later. The upper stage then made two burns. The second one, roughly an hour into the flight, sent MMX out of Earth orbit towards Mars. A launch like this is the riskiest few minutes of the whole mission, so a clean separation is a big relief for JAXA and its partners.

Who is on board

MMX is led by JAXA, with contributions from NASA, ESA, France's CNES and Germany's DLR. CNES and DLR jointly built Idefix, a 25 kg rover. DLR says MMX is the largest Solar System mission JAXA has ever undertaken.

"As I watched the rocket H3 F10 soar into the sky, my thoughts went back to the very beginning of this project more than a decade ago," said Yasuhiro Kawakatsu, JAXA's MMX project manager.

A rover that lands by bouncing

Idefix faces some of the strangest conditions a robot has seen. Gravity on Phobos is less than a thousandth of Earth's, and temperatures swing by more than 200 °C over a day-night cycle that lasts about seven hours. MMX will release the rover from 40–100 metres up. After an unbraked impact and a few bounces, Idefix has to turn itself upright, unfold its solar panels and start a planned 100 days of work, according to DLR.

Why it matters

Scientists still argue over whether Phobos and Deimos are captured asteroids or debris from a giant impact on Mars. Grains of real Phobos soil in a lab should settle that far better than flybys can. If MMX succeeds, it will be the first mission to return material from the Mars system. If you want to look at Mars yourself, a modest scope from our beginner telescope guide will show its disc, though not its tiny moons. For another long-haul cruise in progress, see how ESA's Juice probe used Earth to slingshot towards Jupiter.