MMX Phobos probe: 10 grams of moon dirt, a 2031 return, $578M

The MMX Phobos mission lifted off at 3:41pm EDT on Monday, which was 4:41am on Tuesday, October 20, in Japan. It rode a 207-foot H3 rocket, Japan’s main launch vehicle, flying in a new heavy-lift setup with four solid rocket boosters to carry the country’s heaviest interplanetary probe so far.

About 71 minutes after liftoff, the spacecraft separated from the rocket, contacted mission control and opened its solar panels. JAXA president Hiroshi Yamakawa declared the launch a success, saying a five-year journey had just begun. Project manager Yasuhiro Kawakatsu reported the probe was in a very stable condition.

It was also a confidence boost for the H3. The rocket failed on its first flight in March 2023 and again on flight No. 8 in December 2025, when a second-stage engine shut down early. MMX marked its third success in a row, and the first time an H3 has sent anything beyond Earth orbit.

MMX stands for Martian Moons eXploration, and the trip is long. Here’s the schedule JAXA and its partners have laid out:

• August 2027: MMX enters orbit around Mars after a cruise of roughly 10 months.
• September 2027: It starts circling alongside Phobos, the larger of Mars’ two moons, and studies both Phobos and the smaller moon, Deimos, from a distance.
• Early 2029: It drops Idefix, a 55-pound rover built by France’s CNES and Germany’s DLR space agencies, to scout landing spots.
• 2030: The main spacecraft lands on Phobos twice to collect at least 10 grams of material.
• 2031: A capsule lands in the Australian outback, where scientists will recover it.

Ten grams is about the weight of four US pennies. That sounds tiny, but one NASA scientist called a few grams a real bonanza for researchers. MMX will gather it two ways: one tool drills about two centimeters into the surface, while another blasts pressurized gas at the ground to catch loose grains.

Phobos and Deimos are odd. They are small, very dark and shaped like potatoes, which makes them look like asteroids that drifted too close to Mars and got caught. But their neat, circular orbits suggest something else: that they formed from debris blasted off Mars by a giant impact.

Photos and remote measurements haven’t settled the question, so scientists want the real thing in their labs, where they can use equipment far too big or delicate to send into space. The answer would also help scientists date collisions around Mars, which they currently estimate using a timeline borrowed from our own Moon.

There’s a bonus. Space rocks regularly smash into Mars and spray debris outward, so the Phobos surface may hold stray grains of Mars itself. Spotting them won’t be easy, since they would be microscopic and battered by radiation, but they could come from deeper in the Martian crust than any meteorite found on Earth.

The mission also carries hardware from its partners. Europe supplied the probe’s deep-space radio equipment, and the spacecraft is built in three parts: a propulsion module to reach Mars, an exploration module for the work at Phobos and a return module that will carry the capsule home.

This is a Japanese-led mission, but it has a strong American connection. NASA is a partner alongside France’s CNES, Germany’s DLR and the European Space Agency, which supplied deep-space radio gear and its ground station network. After JAXA catalogs the samples, it will share portions, and 15 percent will end up at NASA’s Johnson Space Center in Houston.

That matters because NASA’s Mars Sample Return plan, meant to fly home the rock cores collected by the Perseverance rover, is in limbo after Congress cut funding for the follow-up mission over rising costs and doubts about launching a rocket off Mars. For now, MMX is the most realistic route for scientists to study material linked to Mars in Earth labs.

Japan has done this before. Its Hayabusa and Hayabusa2 probes were the first two missions to return pristine samples from asteroids, and Hayabusa2’s dust from the asteroid Ryugu turned out to contain building blocks of life. If MMX succeeds, it will also be the first spacecraft to reach Phobos at all. Three earlier Russian attempts failed.