NEW ORLEANS — The launch of a Japanese mission to collect samples from the Martian moon Phobos and return them to Earth, previously scheduled for later this year, has slipped to 2026.

The Japanese space agency JAXA confirmed the two-year delay in the launch of the Martian Moons eXploration, or MMX, mission, blaming it in part on the H3 rocket that will launch the spacecraft.

“Owing to evaluate the demonstration results of the second H3 rocket test vehicle and considering the importance to ensure sufficient time for preliminary verification of MMX on the ground, the launch schedule for Japanese rockets has been reviewed,” the agency said in a Jan. 10 statement to SpaceNews.

The H3 made its inaugural launch in March 2023 but failed to reach orbit when its second stage engine did not ignite, likely because of an electrical issue. JAXA announced Dec. 27 it had scheduled the second H3 launch for as soon as Feb. 14, carrying a test payload and two smallsats.

MMX was scheduled to launch in September 2024. It would have entered orbit around Mars in August 2025 and remained there for three years before heading back to Earth, returning in September 2029.

The decision to delay MMX to 2026, the next available window for a Mars mission, was approved in December by the Japanese government’s Space Development Strategy Headquarters as part of a revision of its Schedule for the Basic Plan on Space Policy. The mission announced the change on social media at the time, but with no explanation for the delay.

MMX is a spacecraft weighing about 4,000 kilograms carrying a suite of instruments to study Mars and its two small moons, Phobos and Deimos. Among them is MEGANE, a gamma-ray and neutron spectrometer being developed in cooperation with NASA. Also on MMX is a small rover jointly developed by the French space agency CNES and German aerospace agency DLR to explore Phobos.

The primary mission of MMX is to touch down on Phobos and collect samples of Phobos for return to Earth. Scientists plan to analyze the samples to determine if Phobos, and likely Deimos, were formed by a collision of a larger object with Mars, or are small asteroids that were captured into orbit by the planet. Under the revised mission schedule, MMX will return the samples to Earth in 2031.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...