Did you know? Mars has 2 moons, and Japan wants to bring a piece of one back

Earth has one moon. Mars has two: Phobos and Deimos. And on 20 October 2026, Japan launched a spacecraft to scoop up some of Phobos and fly it back to Earth.

The mission is called MMX (Martian Moons eXploration). If it works, it will be the world's first mission to return samples from a moon of Mars.

A launch while Malaysia slept

The H3 rocket (flight No. 10) lifted off from the Tanegashima Space Center in southern Japan at 4:41am Japan time. In Malaysia, that was 3:41am, when most of us were fast asleep.

About 1 hour and 11 minutes after liftoff, MMX separated from the rocket and entered its planned orbit. Project leader Yasuhiro Kawakatsu said the spacecraft was in a stable condition.

The mission was originally meant to fly in 2024, but it was pushed back after the H3 rocket's maiden flight failed.

So what exactly is Phobos?

Phobos is the bigger of Mars's two moons, though "bigger" is doing a lot of work here. It's only about 22 km wide, not even round enough to look like a typical moon. Deimos is smaller still, at around 13 km.

Scientists are still arguing over where Phobos came from:

• Theory 1: it's an asteroid that got "captured" by Mars's gravity.
• Theory 2: it's debris flung into orbit after a giant impact on the Martian surface.

Samples from MMX should help settle the debate.

A five-year trip for 10 grams of dirt

This is a long mission. Here's the schedule:

The goal is at least 10 grams of Phobos material. That sounds tiny, but for a science lab it's priceless. The spacecraft itself weighs 4,480 kg, and it will also study Deimos from a distance.

A rover as light as a feather

MMX is an international effort. JAXA leads, with partners NASA, ESA (the European Space Agency), CNES (France) and DLR (Germany). NASA contributed two instruments, including a sampling tool.

France and Germany built a small rover called Idefix, which weighs 25 kg. Its job is to scout the surface of Phobos and help prepare for the main spacecraft's landing.

Did you know? Gravity on Phobos is so weak that Idefix, which weighs 25 kg on Earth, will "weigh" only about 15 grams there. That's lighter than your phone.

Japan has done this before

This isn't Japan's first sample-return rodeo. The Hayabusa mission brought back pieces of the asteroid Itokawa in 2010. About a decade later, Hayabusa2 returned material from the asteroid Ryugu.

If MMX succeeds, Japan will be the first to bring back samples from a moon of another planet, and it will also be the first round trip to the Martian system.

We'll find out in 2031. By then, we may finally know whether Phobos is a lost asteroid or a chunk of Mars itself.