Japan's Martian Moons eXploration (MMX) mission is designed to collect a sample from which of Mars' moons?

The Japan Aerospace Exploration Agency (JAXA) is preparing for an ambitious journey to the Red Planet's vicinity with its Martian Moons eXploration, or MMX, mission, scheduled for launch in 2026. This pioneering mission aims to collect and return a sample from Phobos, the larger and innermost of Mars's two enigmatic moons. This endeavor marks humanity's first attempt to bring material back from the Martian system, offering an unprecedented opportunity to study these celestial bodies up close.

Phobos is an irregularly shaped, dark, and heavily cratered object, measuring approximately 26 by 23 by 18 kilometers. It orbits incredibly close to Mars, at a distance of only about 6,000 kilometers from the planet's surface, completing an orbit in less than eight hours—much faster than Mars itself rotates. The origin of Phobos, along with its smaller sibling Deimos, remains a significant mystery in planetary science. Scientists debate whether these moons are captured asteroids from the outer solar system or if they formed from debris ejected after a large impact on early Mars.

By collecting at least 10 grams of surface material from Phobos, the MMX mission seeks to unlock the secrets of its formation and, by extension, shed light on the early history of Mars and the entire solar system. The returned samples will be meticulously analyzed on Earth, providing crucial insights into the conditions under which planets and their moons form and evolve. This international collaboration, led by JAXA with contributions from NASA, the French space agency CNES, and the German Aerospace Center (DLR), also includes deploying a small rover, Idefix, to explore Phobos's surface. The findings from MMX will not only advance our understanding of Mars but also contribute to the broader picture of how water and organic materials, essential for life, originated in the terrestrial planets.