Martian Moons eXploration (MMX)

At a glance

Key points

• Launch scheduled 19 Oct 2026
• Phobos sample due on Earth in 2031
• Will survey both Martian moons

Captured asteroid or impact debris?

Phobos and Deimos are dark like primitive asteroids, but their circular, equatorial orbits look like the debris of a giant impact on Mars. A sample settles it: impact material would carry Martian chemistry.

The mission plan

After roughly a year in transit, MMX is due to reach Mars in 2027 and spend about three years in the moons' neighbourhood. It will map Phobos in detail, observe Deimos, release a small rover and then touch down itself to collect material. The return module leaves Mars in 2030, and a capsule carrying the sample is planned to land in Australia in 2031, where JAXA also recovered the Hayabusa2 capsule from asteroid Ryugu.

A rover for a moon with almost no gravity

Idefix, about the size of a crate of drinks, is planned to drop in free fall from roughly 40 m above Phobos, then right itself on its own. Surface gravity there is less than a thousandth of Earth's, so even driving is tricky. Over about 100 days its Raman spectrometer, radiometer and cameras will study the surface, and the way its wheels sink in will tell JAXA how the regolith behaves before the main spacecraft lands.

Launch window

Mars and Earth line up for an efficient transfer only about every 26 months. MMX's slot opens with a planned launch at 19:41 UTC on 19 October 2026 (04:41 JST on the 20th) from Tanegashima, on H3 Flight 10, and the window runs to 7 November. Missing it entirely would mean waiting for the next alignment.

What we still don't know

Phobos's interior structure, and how much of its regolith is Martian material blasted off the planet over billions of years.

Missions

1. Launch 19 Oct 2026

   Martian Moons eXploration (MMX)

   JAXAPlanned

   H3 F10 from Tanegashima at 19:41 UTC (window to 7 Nov). Phobos operations 2027–2030, sample return 2031.

   Mission page (opens in a new tab)

Related entries

• PhobosMars's doomed inner moon
• DeimosMars's small, smooth outer moon
• MarsCold desert with an ancient wet past

Sources

1. JAXA press release, Aug 2026 (opens in a new tab)
2. JAXA MMX mission site (opens in a new tab)
3. DLR: MMX and the Idefix rover ready for launch (opens in a new tab)

Last reviewed 10 Oct 2026 against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.