How will MMX study the martian moons?
MMX will launch in 2024 and enter Mars orbit a year later. It will gradually get closer to Phobos, entering what mission planners call a quasi-orbit: while it may look like MMX is orbiting Phobos, it is actually just orbiting Mars in a way that lets it circle Phobos at the same time. This will be no easy challenge, since Phobos is deep inside Mars’ gravity well and just 6,000 kilometers above the surface (Earth’s Moon is more than 60 times further away).
MMX will spend a year studying Phobos with its remote science instruments while searching for a safe and scientifically interesting place to land. A wide-angle camera and laser mapping system will map the moon in 3D, while a narrow-angle camera provides a closer look at specific areas. Three spectrometers, two of which are international contributions from the French space agency CNES and NASA, will determine the mineral and elemental makeup of Phobos’ surface. A dust sensor will also look for orbiting particles knocked off Mars and Phobos by meteor impacts. The spacecraft also includes a pair of ultra-high-resolution video cameras from the Japanese Broadcasting Corporation that will provide stunning views of Mars and its moons. Some images will be transmitted to Earth during the mission, with the rest stored in the sample return capsule for later playback.
As MMX descends to Phobos for landing, it will deploy a small German and French-built rover based on the MASCOT, which Hayabusa2 dropped to tumble around asteroid Ryugu. The rover will travel around Phobos for at least 100 days analyzing the surface.
We don’t know exactly what Phobos’ surface is like: is it rocky, fluffy, or sandy? MMX is prepared for a variety of possibilities with two sampling devices called C Sampler and P Sampler. C Sampler is a robotic-arm-mounted drill that can bore 10 centimeters beneath the surface. P Sampler works by releasing pressurized gas to kick up surface materials, which travel through a tube into a collection container.
P Sampler is a derivative of Honeybee Robotics’ PlanetVac, a Planetary Society-supported technology designed to simplify and lower the cost of sample collection. Our members and supporters funded PlanetVac tests in 2013 and 2018, demonstrating its readiness for use on future space missions. NASA is including the technology on a 2023 commercial Moon flight, and is contributing P Sampler to Japan for the 2024 MMX mission.
Once MMX collects its samples, it will lift off from Phobos and begin spiraling out of Martian orbit, passing Deimos several times on its way out to analyze and map the smaller moon. MMX will leave Mars in 2028 and return to Earth in 2029. The spacecraft will jettison a small capsule containing the samples, which will plummet through Earth’s atmosphere and use a parachute to land safely for collection.