Japan’s Long Road Back to Mars

After decades of setbacks, Japan is assembling the technology, partnerships and patience required for a return to the Red Planet, and for a role in the next era of planetary exploration. The first sign may be a faint radio signal crossing millions of miles of darkness.

At a control room in Japan, engineers will wait for confirmation that a spacecraft has survived the journey from Earth, entered the Martian system and begun the most delicate phase of its mission: collecting material from one of Mars’s small moons and bringing it home.

If successful, the mission will do more than return a few grams of rock and dust. It will mark Japan’s most ambitious attempt yet to reach Mars and establish the country as a central player in the international effort to understand the planet’s history, its moons and the possibility that life once existed there.

Japan’s Mars exploration programme has been shaped by failure as much as by achievement. Its first interplanetary mission to Mars, Nozomi, was launched in 1998 but never entered orbit after a series of technical problems. More than two decades later, the country’s Hayabusa2 mission returned samples from the asteroid Ryugu, demonstrating that Japan could navigate to a distant body, land on it, collect material and deliver that material safely to Earth.

The next step is Mars.

Japan’s Martian Moons Exploration mission, known as MMX, is designed to visit Phobos, the larger of Mars’s two small moons, collect samples and return them to Earth. The mission is being led by the Japan Aerospace Exploration Agency, or JAXA, with participation from international partners including NASA and the French space agency, CNES.

The spacecraft is expected to launch in the late 2020s, with the sample return planned for the early 2030s. Its central scientific question is deceptively simple: Where did Phobos come from?

The answer could help explain the origin of Mars itself.

A planet that keeps its secrets

Mars has fascinated scientists because it is both familiar and alien. It has seasons, polar ice caps, volcanoes, valleys and evidence that liquid water once flowed across its surface. Yet its atmosphere is thin, its surface is cold and dry, and its present environment is hostile to life as we know it.

Robotic spacecraft have been studying Mars since the 1960s. The Soviet Union’s Mars programme achieved early flybys and landings, though many missions failed. NASA’s Mariner 4 returned the first close-up images of Mars in 1965, revealing a cratered world that looked more like the Moon than the Earth-like planet some had imagined.

Later missions transformed that picture. Orbiters mapped ancient channels and mineral deposits associated with water. Landers and rovers examined rocks and soil. NASA’s Curiosity rover, which landed in 2012, found evidence that Gale Crater once contained a lake capable of supporting microbial life. The Perseverance rover, which arrived in 2021, has been collecting and sealing rock samples for a future mission intended to return them to Earth.

Mars is now the most heavily explored planet beyond Earth, but major questions remain unresolved. Scientists do not know whether life ever emerged there, how long habitable conditions lasted or why Mars lost much of its atmosphere and surface water.

The planet’s two moons may provide part of the answer.

Phobos and Deimos are small, irregular bodies. Their origins are disputed. One theory holds that they are asteroids captured by Mars’s gravity. Another suggests that they formed from debris blasted into orbit after a massive impact on Mars. A third possibility is that they are remnants of Mars itself, assembled from material ejected by ancient collisions.

A sample returned from Phobos could reveal which explanation is most plausible.

Because Phobos is close to Mars and may contain material from the planet’s surface, its soil could also preserve clues about Martian geology. The moon’s low gravity makes landing and departing easier than operating from Mars itself, allowing MMX to study the Martian system without attempting a full landing on the planet.

Japan’s first attempt

Japan’s interest in Mars is not new.

In 1998, JAXA launched Nozomi, a spacecraft intended to study the Martian atmosphere and its interaction with the solar wind. The mission was Japan’s first attempt to send a spacecraft to Mars and enter orbit around another planet.

Nozomi encountered trouble soon after launch. A malfunction affected its propulsion system, and a later solar flare damaged electrical components. Engineers redesigned the spacecraft’s trajectory to conserve fuel, but the revised plan delayed its arrival. By 2003, the spacecraft no longer had enough power or propellant to achieve its mission. JAXA abandoned the attempt, and Nozomi passed by Mars without entering orbit.

The failure was a setback, but it also exposed the difficulty of interplanetary exploration. A spacecraft traveling to Mars must operate for years, withstand radiation and extreme temperature changes, communicate across vast distances and perform precise maneuvers with little room for error.

Japan’s next major planetary mission, Hayabusa, was aimed not at Mars but at the near-Earth asteroid Itokawa. Launched in 2003, Hayabusa became one of the most technically demanding robotic missions ever attempted. It suffered engine failures, communication problems and difficulties during its landing and sample collection. Yet in 2010, its return capsule came back to Earth carrying particles from the asteroid.

The mission’s success changed Japan’s standing in planetary exploration. It showed that a spacecraft could travel to a small, distant body, operate around it and return material to Earth despite a cascade of failures.

Hayabusa2 extended that achievement. Launched in 2014, it reached the asteroid Ryugu in 2018. The spacecraft deployed small rovers, fired an impactor into the asteroid’s surface and collected samples from both the surface and a newly created crater.

In December 2020, its return capsule landed in Australia. Scientists found carbon-rich material and organic compounds in the samples, offering new evidence about the chemistry of the early solar system. The spacecraft itself continued into a new mission, visiting another asteroid after releasing the capsule.

For JAXA, Hayabusa2 was more than a scientific success. It was a demonstration that Japan had developed a distinctive capability: precision exploration of small bodies and the return of extraterrestrial material to Earth.

MMX is intended to apply that experience to the Martian system.

The mission to Phobos

MMX will travel to Mars, enter orbit around the planet and study both Phobos and Deimos from a distance. It will then descend toward Phobos, collect at least several grams of surface material and return the sample to Earth.

The spacecraft is expected to include a suite of cameras and scientific instruments to examine the moon’s surface, composition, internal structure and environment. A small rover developed with European partners is planned to operate on Phobos before the main spacecraft conducts its sampling operations.

The mission’s design reflects the unusual nature of Phobos. The moon is only about 27 kilometers across at its widest point, and its gravity is extremely weak. A spacecraft approaching its surface must move slowly and carefully. Dust and loose material could complicate landing and sampling. The spacecraft must also navigate in the gravitational environment created by both Mars and Phobos.

The sample-return phase will be especially demanding. After collecting material, MMX must leave Phobos, depart the Martian system and travel back to Earth. Its return capsule will then enter the atmosphere at high speed and land for recovery.

The mission is expected to return more material than Hayabusa2 did, but the scientific value will not depend only on quantity. Researchers will want to know whether the sample resembles known asteroid types, contains minerals altered by Mars or preserves material from an ancient impact.

The results could settle a question that has remained open since the moons were discovered in the 19th century.

A partnership built around Mars

Japan is not pursuing the mission alone.

NASA is contributing a scientific instrument and plans to provide communications support. CNES is involved in the development of the rover, while Germany is also participating in the rover effort. The international structure reflects the cost and complexity of modern planetary exploration, in which no single country necessarily supplies every instrument, launch service or communications system.

The partnership also gives MMX a role in a larger network of missions focused on Mars.

NASA’s Perseverance rover is collecting samples in Jezero Crater, where an ancient river delta may have preserved evidence of past habitability. NASA and the European Space Agency have been developing a Mars Sample Return campaign to bring those samples to Earth, though the programme has faced technical and financial challenges.

China’s Tianwen-1 mission entered orbit around Mars in 2021, landed the Zhurong rover and demonstrated China’s ability to conduct an orbital, landing and surface mission in a single campaign. India’s Mars Orbiter Mission, launched in 2013, reached Mars orbit in 2014 and operated for years, giving India its first successful interplanetary mission.

The United Arab Emirates’ Hope probe entered Mars orbit in 2021 to study the planet’s atmosphere and climate. Private companies are also developing technologies that could eventually support commercial or human missions, though sending people to Mars remains far more difficult than robotic exploration.

Against that backdrop, Japan’s contribution is distinctive. It is not attempting to land a large rover on Mars or establish an orbital communications network. It is targeting a small moon whose material may answer fundamental questions about the formation of the Martian system.

The cost of returning a sample

A sample-return mission is more complicated than a flyby or an orbital survey because every stage must work in sequence.

The spacecraft must launch successfully, reach its destination, operate for years, collect material, preserve it, depart and return. A failure at any point can end the mission.

The scientific payoff, however, is unusually high. Instruments on a spacecraft can analyze only what they can measure remotely or in limited quantities. Laboratories on Earth can apply techniques that are too large, delicate or power-intensive to send into space. They can also reanalyze samples as new technologies become available.

That is why sample return has become a central goal of planetary science. The Apollo missions returned lunar rocks that transformed understanding of the Moon. Stardust brought particles from a comet’s tail. Hayabusa and Hayabusa2 returned material from asteroids. NASA’s OSIRIS-REx delivered a large sample from the asteroid Bennu in 2023.

Mars presents a more difficult case because of planetary-protection concerns. Any material returned from Mars or its moons must be handled under strict conditions to prevent contamination of Earth and to preserve the scientific integrity of the sample.

Phobos is not believed to host life, but its proximity to Mars means that its surface may contain material ejected from the planet. Researchers will therefore study the sample not only for clues about the moon but also for possible Martian material.

Why Japan is investing in Mars

Japan’s Mars programme is scientific, but it is also industrial and strategic.

Planetary missions require advanced propulsion, autonomous navigation, robotics, communications, thermal control, materials engineering and precision manufacturing. The technologies developed for space exploration can strengthen capabilities in other sectors, including aerospace, electronics and robotics.

Japan has long used space missions to cultivate those capabilities. Its scientific spacecraft are often smaller than the largest American or European missions, but they have pursued technically ambitious objectives, including asteroid rendezvous, sample return and solar-sail experimentation.

The country’s space policy has also become more closely connected to national security and economic competition. Japan is expanding cooperation with the United States and other partners as space becomes more crowded and strategically important. Civilian planetary exploration remains distinct from military activity, but the same industrial base supports both.

Mars is also becoming a test of international influence. The countries that can send spacecraft to the planet, operate them reliably and return samples will shape the scientific agenda for decades.

Japan’s role in MMX gives it a place in that effort without requiring it to duplicate every capability developed by NASA, China or Europe.

The limits of the mission

MMX will not answer every question about Mars.

It will not drill deep into the planet, search directly for living organisms or determine whether humans could survive there. It will not replace the work of rovers, orbiters or future astronauts.

Its importance lies in the questions it can address. If Phobos formed from an impact on Mars, its material may preserve a record of the planet’s early history. If it is a captured asteroid, the sample could connect the Martian moons to the population of small bodies that populated the early solar system. If the evidence is mixed, scientists may need to revise their models again.

The mission could also reveal how material moves between Mars and its moons. Dust and debris thrown from the Martian surface by impacts may settle on Phobos, creating a natural archive of the planet’s geological past.

But the mission faces risks. Launch schedules can change. Spacecraft systems can fail. The Martian environment is unforgiving, and the navigation required around a small moon is difficult. Japan’s history at Mars includes a prominent failure, and the country’s sample-return successes have depended on years of engineering and careful recovery operations.

The mission’s planners know that a successful launch will be only the beginning.

A return measured in decades

The history of Mars exploration is a history of persistence.

The first missions often failed. Some spacecraft never left Earth orbit. Others lost contact, missed their targets or crashed during landing. Yet each attempt added knowledge, improved engineering and made the next mission possible.

Japan’s path has followed that pattern. Nozomi did not reach Mars orbit, but its failure became part of the country’s experience in interplanetary navigation. Hayabusa survived a series of crises and returned asteroid particles. Hayabusa2 refined the techniques needed to approach, touch and depart from a small body.

MMX represents the next link in that chain.

If it succeeds, Japan will have returned samples from an asteroid and from the Martian system, two of the most difficult categories of robotic exploration. It will also have helped establish whether Mars’s moons are captured asteroids, impact debris or something more complicated.

The answer may arrive in a laboratory years after the spacecraft leaves Phobos. Scientists will examine grains too small to see with the naked eye, compare their chemistry with Martian meteorites and asteroid samples, and reconstruct events that occurred billions of years ago.

For Japan, the mission’s meaning will be measured not only by the material brought home but by the capability built along the way.

A spacecraft crossing the darkness between Earth and Mars will carry the country’s history of failed attempts, improbable recoveries and carefully accumulated expertise. Its destination will be a small moon orbiting a planet that has resisted easy explanation.

And when the signal finally arrives, the first question will be the same one that has driven Mars exploration for generations: What happened there, and what can the response tell us about the worlds that came before our own?

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