Japan's space agency is preparing to dispatch a probe on a five-year journey to the moons of Mars, with the launch vehicle itself marking a notable test of the country's rocket programme. Set for an October 20 departure, JAXA's Martian Moons eXploration probe — known by its MMX designation — will lift off aboard an H3 rocket at 1:11 am IST, with Tanegashima Space Centre serving as the departure point.

Designed to collect surface material from Phobos and return it to Earth by 2031, the probe draws on contributions from NASA and a range of international partners while also turning its instruments toward Deimos, the second of Mars's two small moons.

Built through a partnership between JAXA and Mitsubishi Heavy Industries, the H3 represents the next generation of flagship launch vehicles for Japan's space programme. Built to take over from the ageing H-IIA rocket, the new vehicle aims to bring down the cost of putting satellites into orbit while offering operators greater scheduling flexibility.

Reaching heights of up to 63 metres depending on how it is assembled, the H3 rocket accommodates varying numbers of engines and solid rocket boosters to match the demands of each individual mission. A stripped-down configuration without solid rocket boosters carries a listed launch price goal of USD 30 million or above, according to JAXA's published targets. The figure represents an intended goal for that specific setup, not a verified price tied to the MMX rollout.

JAXA has disclosed that the programme's spending allocation climbed from a starting point of USD 1.2 billion to a figure exceeding USD 1.5 billion as the rocket took shape. Securing a home-grown launch capability forms one pillar of the funding, with the other aimed at opening doors to contracts in the commercial satellite market.

Tasked with carrying the MMX spacecraft beyond Earth's orbit, the H3 rocket serves as the vehicle that places the probe on a trajectory bound for Mars. At the point of spacecraft separation, the booster's function concludes.

Scheduled to spend roughly a year in transit before arriving at the Martian system in 2027, MMX will survey both moons, gather no fewer than 10 grams of surface material from Phobos, and deliver those specimens back to Earth by 2031.

Troubles along the H3 programme's development path included a launch attempt in March 2023 that ended without success. Gains were recorded across follow-on flights, though a formal inquiry was opened after the eighth attempt ended in failure.

Results from the MMX mission will help shape the direction Japan's space programme takes next. Alongside that primary assignment, the H3 rocket is designed to carry scientific instruments and commercial satellites into orbit, giving Japan a self-reliant pathway to space while staking out a position in the broader international launch industry.