Japan launches MMX probe to collect first samples from Mars moon Phobos

The Japan Aerospace Exploration Agency (JAXA) launched the Martian Moons eXploration (MMX) spacecraft at 4:41:03 a.m. Japan Standard Time on October 20, 2026, from the Tanegashima Space Center, according to JAXA's official mission site. In U.S. time, the liftoff occurred at 3:41 p.m. EDT on October 19, 2026, spacepolicyonline.com reported.

The probe rode into space aboard an H3 rocket, flight number 10, built by Mitsubishi Heavy Industries. JAXA describes MMX as "a world-first sample return mission to the Martian sphere," targeting Phobos, the larger and closer of Mars's two small moons.

What the mission will do

According to JAXA, MMX will spend roughly a year traveling to the Mars system, arriving around August 2027. It will then operate in the vicinity of Phobos and Deimos through 2030 before beginning a roughly one-year return trip, with the sample capsule planned to land in Australia in 2031, per spacepolicyonline.com.

The spacecraft is built from three modules — propulsion, exploration and return — and measures about 9.0 meters long, 4.5 meters wide and 5.3 meters high, JAXA states. Plans call for two soft-landing touchdowns on Phobos to collect a combined total of more than 10 grams of surface and subsurface material using thirteen scientific instruments.

International contributions

MMX carries hardware from several countries, which JAXA calls "the largest international collaborative mission in lunar and planetary exploration ever led by Japan." NASA contributed two instruments, according to spacepolicyonline.com: MEGANE, a gamma-ray and neutron spectrometer built by the Johns Hopkins University Applied Physics Laboratory to measure Phobos's elemental composition, and the P-Sampler, a pneumatic sample-collection device made by Honeybee Robotics, a Blue Origin subsidiary.

Germany's DLR and France's CNES space agencies jointly built Idefix, a 25-kilogram four-wheeled rover equipped with solar panels and a rechargeable battery. Idefix is designed to operate for up to 100 hours on Phobos, scouting terrain ahead of the lander's sampling attempts, spacepolicyonline.com reported.

Why scientists want Phobos samples

The central scientific question is how Phobos and Deimos formed. According to background on German Wikipedia's Phobos entry, one long-standing hypothesis holds that the irregular-shaped moons are asteroids captured by Mars's gravity from the outer asteroid belt; an alternative holds that Phobos and Deimos are remnants of an older Martian moon that broke apart, with orbital calculations suggesting the two moons' orbits would have coincided within roughly the last 2.7 billion years. JAXA states the mission aims to "uncover the origin of the Martian moons and investigate how the planetary formation process unfolded," including how water and organic materials may have reached rocky planets.

According to German Wikipedia's Phobos entry, the moon orbits only about 9,378 kilometers from the center of Mars, less than 6,000 kilometers above the Martian surface, completing a lap every 7 hours and 39 minutes — fast enough that, as seen from Mars, it rises in the west and sets in the east. Phobos measures roughly 27 by 22 by 18 kilometers and has a density of 1.887 g/cm3, figures cited in the debate over whether it is a solid captured asteroid or a loosely packed pile of impact debris.

What happens next

MMX is JAXA's third sample-return mission, following Hayabusa, which returned material from the asteroid Itokawa in 2010, and Hayabusa2, which returned material from the asteroid Ryugu in 2020, according to spacepolicyonline.com. The spacecraft's health and trajectory will be monitored over the coming months as it heads toward Mars, with arrival expected around August 2027 and a landing attempt on Phobos not expected before December 2028, spacepolicyonline.com reported.