Japan’s MMX Phobos sample-return mission is set for an October 20 launch

A closer look at Phobos

The spacecraft will spend several years operating near Phobos. JAXA plans to place MMX in a quasi-satellite orbit around the moon for detailed observations.

From there, MMX will map the moon’s surface and measure its topography, composition, gravity and internal structure. The mission plan calls for two soft landings and the collection of more than 10 grams of regolith. MMX will also observe Deimos during the mission’s final phase near Mars.

The spacecraft is scheduled to leave the Mars system in 2030 and release its sample capsule for recovery in Australia in 2031. If successful, the material would become the first sample returned to Earth from the Martian sphere.

The mystery inside the sample

Scientists have two leading ideas about how Phobos and Deimos formed. The moons may be ancient asteroids captured by Mars’s gravity, or they may have formed from debris thrown into orbit by a massive impact on Mars.

The answer could help scientists reconstruct the early history of the Mars system and better understand how material, including water and organic compounds, moved through the solar system. JAXA says detailed observations and analysis of the returned grains could clarify the formation of the Martian moons and the evolution of the solar system.

The NASA-supported instruments aboard MMX include the MEGANE spectrometer, which will measure gamma rays and neutrons to identify elements on Phobos, and a pneumatic sampler designed to gather surface material with bursts of nitrogen gas. NASA will also provide Deep Space Network support and expects to curate about 15 percent of the returned sample at Johnson Space Center.

JAXA describes MMX as a five-year mission. Its published schedule runs from launch through a 2031 return, but the dates remain mission targets and could change as launch and flight operations unfold.