JAXA's MMX Mission Targets Landing on Martian Moon Phobos
The ambitious MMX mission aims to collect surface samples from the mysterious Martian moon Phobos.
1Ambitious Martian Exploration
The Martian Moons eXploration mission, launched on 20 October 2026, aims to reach Phobos by 2027. This international effort involves JAXA, NASA, and European agencies. The primary goal is to solve the mystery of Phobos's origins, which remains an enigma for planetary scientists studying the wider solar system's history.
2The Rubble Pile Moon
Phobos is a lumpy, potato-shaped body measuring roughly 27 kilometers in length. It is considered a loosely consolidated rubble pile with only 1/1,800th of Earth's gravity. Scientists hypothesize it was either a captured asteroid or formed from debris ejected after a massive celestial body slammed into the planet Mars.
3Complex Modular Design
The MMX spacecraft consists of three distinct modules: a propulsion module for transit, an exploration module for surface operations, and a return module for Earth reentry. After collecting samples, the exploration module is jettisoned, allowing the return module to carry the 10-gram sample capsule back to Earth by late 2031.
4Navigating Microgravity Orbits
Because Phobos is too small for conventional orbits, MMX will follow a quasi-satellite path. The spacecraft will move in an egg-shaped trajectory, alternating between positions ahead of and behind the moon. This clever maneuver allows the craft to maintain proximity while managing the complex gravitational influence of the nearby planet Mars.
5Mapping the Surface
During a two-year remote sensing campaign, MMX will loop at distances ranging from 200 kilometers down to 20 kilometers. Using cameras and a laser altimeter, the mission will create high-resolution maps to identify safe landing sites. These observations are critical for navigating the moon's rugged, poorly understood surface terrain.
6The First Penguin Rover
The Idefix rover, developed by French and German agencies, acts as a scout for the main mission. Released from an altitude of 40 to 100 meters, it will freefall toward the surface. Its design lacks traditional landing gear, relying instead on articulated legs to right itself after an expected series of bounces.
7Slow Motion Exploration
Once operational, Idefix will move at a speed of only one millimeter per second. Its wheels feature protruding blades designed to gain traction in the moon's negligible gravity. If driven faster, the rover would essentially swim through the loose regolith rather than rolling across the surface of the small moon.
8WheelCam Data Analysis
Two cameras placed on the underside of Idefix will observe the wheels and their tracks during the 100-day mission. These images help researchers study the size, distribution, and cohesion of grains in the regolith. Understanding these mechanical properties is essential for predicting how the main spacecraft will interact with the surface.
9Ground Truth for Landing
Idefix provides essential ground truth, filling the gap between orbital observations and physical sample analysis. Its findings regarding surface porosity and strength will inform the final landing strategy for the larger exploration module. This data helps mitigate risks associated with the loose, unpredictable material found on the surface of Phobos.
10Controlled Freefall Landing
The main exploration module will descend to 10 meters before entering a controlled freefall. Given the extremely low gravity, any lateral motion could cause the lander to tip or bounce. The mission draws on experience from Japan’s Hayabusa missions, which successfully landed on asteroids Itokawa and Ryugu in previous years.
11Dual Sampling Strategy
MMX utilizes two distinct sampling devices to ensure success. A robotic coring sampler will dig at least two centimeters below the weathered surface to retrieve pristine material. Additionally, a pneumatic sampler will inject nitrogen gas to capture loose surface grains, providing redundancy and a broader range of scientific data for analysis.
12Scientific Legacy Potential
By analyzing samples from beneath the surface, researchers hope to bypass material battered by cosmic radiation. This mission represents the most complex attempt to date at exploring a microgravity moon. If successful, the returned samples will provide unprecedented insights into the evolution of the Martian system and the solar system.
Original article: IEEE Spectrum — JAXA's MMX Mission Targets Landing on Martian Moon Phobos