1. What is MMX? Japan's Flagship Planetary Exploration Mission

This morning (October 20, 2026, at 04:41:03 JST), the Japan Aerospace Exploration Agency (JAXA) and launch provider Mitsubishi Heavy Industries (MHI) will embark on one of the most audacious deep-space missions of the decade: the launch of **MMX (Martian Moons eXploration)** from the Tanegashima Space Center.

MMX will rendezvous with Mars' two natural satellites, **Phobos** and **Deimos**, touch down on the surface of Phobos to collect pristine regolith, and return those samples safely to Earth. Harnessing the world-renowned sample-return legacy established by Hayabusa and Hayabusa2, MMX aims to accomplish the **first-ever sample return from the Martian system**.

2. Why Explore the Moons? Solving Satellite Origins & Sampling Ancient Mars

Why target small planetary moons rather than descending onto Mars itself? Planetary scientists point to two monumental scientific mysteries waiting to be solved:

① Settling the Debate: Captured Asteroids or Giant Impact?

How Phobos and Deimos formed remains an intense, century-old debate:

• Captured Asteroid Hypothesis: Small bodies originating from the asteroid belt were captured by Mars’ gravitational field.
• Giant Impact Hypothesis: A massive protoplanet struck Mars, and the resulting debris disk accreted into the moons.

By measuring the isotopic and elemental composition of returned regolith in terrestrial clean rooms, scientists will definitively determine the origin of the moons, shedding light on the early volatile delivery and collision dynamics of the inner solar system.

② Phobos as a Natural "Time Capsule" for Ancient Mars

Phobos orbits exceptionally close to Mars—roughly 6,000 km above its surface. Throughout cosmic history, countless asteroid impacts on Mars ejected crustal material, ancient atmospheric gases, and primordial water into space, a portion of which rained down onto Phobos over billions of years.

Consequently, collecting regolith from Phobos allows scientists to **indirectly sample ancient Martian surface and atmospheric material**, offering profound insights into the evolution of Martian habitability without the extreme fuel penalties of landing on and lifting off from Mars' deep gravity well.

3. Modular 4-Ton Architecture & Redundant Dual Sampling Systems

With a launch mass of approximately 4 tons, MMX is the largest and heaviest deep-space probe Japan has ever constructed. It employs a three-module architecture designed to shed mass as each phase completes:

• Propulsion Module (PM): Delivers the high-delta-V burns required for trans-Mars injection, cruise, and Mars orbit insertion.
• Exploration Module (EM): The scientific nervous system housing landing legs, cameras, spectrometers, and sampling mechanisms.
• Return Module (RM): Houses the sample container and the Earth re-entry capsule.

Dual Redundant Sampling Mechanisms

To guarantee successful sample acquisition, MMX carries two distinct mechanisms:

• Core Sampler (EM Robotic Arm): Drills over 2 cm below the surface to extract pristine, unweathered subsurface regolith cores.
• Pneumatic Sampler: Built into the landing footpads, firing high-pressure nitrogen gas bursts upon contact to loft surface dust directly into collection chambers.

4. The French-German "IDEFIX" Rover: Scouting the Phobos Surface

MMX carries a compact rover named **IDEFIX**, jointly developed by CNES (France) and DLR (Germany).

Released from an altitude of tens of meters prior to the main spacecraft's landing, IDEFIX will free-fall to Phobos' surface, upright itself autonomously, and roll across the low-gravity terrain. By measuring soil mechanical properties and capturing microscopic imagery of wheel interactions, IDEFIX directly de-risks MMX's subsequent touchdown.

5. Mitsubishi Heavy Industries and H3-24L: The Maiden Interplanetary Flight

Today's launch represents a defining milestone for Mitsubishi Heavy Industries (MHI) and Japan's flagship rocket family:

• First Flight of the Maximum-Thrust "H3-24" Variant: Powered by two LE-9 core liquid engines and **four solid rocket boosters (SRB-3)**, delivering maximum payload capability.
• Type-L Long Fairing: A stretched composite fairing shielding the four-ton MMX spacecraft during aerodynamic ascent.
• H3's First Interplanetary Escape Trajectory: Executing a critical second-stage multi-burn restart sequence to escape Earth orbit and place MMX on a trans-Mars injection trajectory.

6. Mission Roadmap to 2031 Earth Return & 3D Tracking on SatViewer3D

The mission timeline spans nearly a decade of precision spaceflight:

• October 20, 2026: Launch from Tanegashima into trans-Mars trajectory
• 2027: Mars Orbit Insertion (MOI) and quasi-satellite orbit around Phobos
• 2028–2029: Phobos touchdown, sample collection, and Deimos flybys
• 2030: Trans-Earth Injection (Mars departure)
• July 2031: Sample capsule recovery in Woomera, Australia