Japan aims to solve a space mystery with a grain of dust

Japan is preparing to launch a spacecraft on a journey to one of the most mysterious destinations in our solar system: Phobos, the larger of Mars's two small moons. The Martian Moons eXploration mission, known as MMX and led by the Japanese space agency Jaxa, aims to become the first mission ever to collect a sample from this moon and bring it safely back to Earth. The spacecraft is scheduled to blast off from the Tanegashima Space Center on a new H3 rocket.

The target is an unusual world. Phobos and its smaller sibling Deimos are tiny, irregularly shaped bodies that some scientists compare to space potatoes. Phobos is only about 20 kilometres across and has very little gravity, which makes landing on it an enormous technical challenge. However, its closeness to Mars is exactly what makes it so interesting to researchers. Scientists believe that over billions of years, material thrown up from the surface of Mars during asteroid strikes may have travelled the short distance and become implanted in the surface of Phobos.

As a result, the 10 grams of dust that MMX plans to collect could contain a double prize: pieces of Phobos itself and tiny grains of Mars. Experts say this material would be pristine, completely untouched by Earth's environment. This is a major advantage over Martian meteorites, which are pieces of Mars that have fallen to our planet but become contaminated by our air, water and soil as soon as they arrive.

A key goal of the mission is to solve a long-standing puzzle about how the two Martian moons formed. One theory suggests that a large object crashed into Mars early in its history, and Phobos and Deimos were created from the resulting debris. Another possibility is that they are wandering asteroids that were captured by the Red Planet's gravity. Researchers say that analysing the sample's chemistry and mineral composition will quickly provide the answer, as the two hypotheses would produce very distinct results.

The mission involves close international cooperation. A small rover developed by France and Germany will land first to explore the terrain and scout a suitable site for the main spacecraft. Once on the surface, the MMX lander will use a robotic arm and two different sampling methods, including one provided by NASA, to collect surface dust and material from just below the ground. After spending about three years in the Mars region and also flying by Deimos to gather observations, the spacecraft's return module will head home, with the precious sample expected to land in the Australian desert in 2031.

Project leaders describe Phobos as one of the most important unexplored places in the solar system. They hope the data gathered will not only answer questions about the moons' origins, but also provide useful information for future human missions to Mars. The mission's project manager has noted that the moons could potentially serve as a base for astronauts. While the sample is tiny, scientists emphasise that even individual grains can be studied in great detail, making every single gram worth the extraordinary effort.