Japan’s MMX Readies to Launch Toward Phobos With U.S. Instruments Onboard

The mission will collect and return material that scientists will use to test whether Mars’s moons formed from a giant impact or are captured asteroids.

Overview

JAXA is targeting liftoff from Tanegashima on Monday, Oct. 19 EDT (Oct. 20 JST) as final prelaunch checks finish and the spacecraft prepares for its interplanetary cruise.
NASA confirmed it is contributing the MEGANE gamma‑ray and neutron spectrometer, the P‑Sampler pneumatic collection system, and Deep Space Network support, and will curate about 15% of returned material at Johnson Space Center.
The MMX spacecraft has three modules, carries 11 science instruments, will deploy a 25 kg rover named Idefix, and uses two complementary samplers — JAXA’s coring C‑Sampler and NASA’s surface P‑Sampler — to collect surface and near‑surface material.
After launch the craft will arrive at Mars in August 2027 to survey Phobos, attempt sample collection no earlier than December 2028, and return the sealed sample container to Earth in 2031.
Returned material should let researchers test competing origin ideas — a giant impact versus capture of primitive asteroids — and the international curation plan and long‑term sample access will shape decades of follow‑up studies.