Japan launches MMX spacecraft to bring back samples from Mars's moon Phobos

Japan has launched the Martian Moons Exploration (MMX) spacecraft, the Japan Aerospace Exploration Agency (Jaxa) said. The probe, carried by Japan's flagship H3 rocket, lifted off before dawn at 4:41am from the Tanegashima Space Centre on Tanegashima island in the country's far south-west. Thousands of people got up early to watch a livestream. About an hour later, Jaxa scientists declared the launch a success when the spacecraft separated from the rocket's upper stage, and the flight control room celebrated.

The goal is to reach Mars's orbit in August next year and collect at least 10g of soil and rock from the surface of Phobos, one of Mars's two small, potato-shaped moons. Phobos is pock-marked, 14 miles (22.5km) across, and orbits Mars three times a day about 6,000km above its surface. The samples are scheduled to come back to Earth in 2031, according to Jaxa. The article says this is the first time anyone has attempted to land on Phobos or the smaller moon, Deimos. For comparison, Nasa has landed nine spacecraft on Mars over the past half a century, and China landed on the Martian surface in 2021.

Five space agencies are collaborating on the five-year, $578m mission. It centres on a five-tonne spacecraft that will sync with Phobos's tight orbit around Mars when it arrives next summer. The craft will first eject a small French-German rover named Idefix, after the white terrier in the Asterix comics. If all goes according to plan, the four-wheeled rover will bounce for several minutes on the surface before halting, because gravity on Phobos is 1/1,000th as strong as on Earth. It will then spend 100 days surveying the surface to find safe landing and sampling sites before the main craft arrives. That main craft is a four-legged stationary lander. It will spend only two hours on Phobos drilling and vacuuming up material before launching back into space. Officials said it would observe Deimos during several flybys before leaving Mars's orbit in November 2030.

Scientists hope the samples will show how Phobos and Deimos formed and may even offer clues about the origins of life. Two ideas compete. The "giant impact" hypothesis says the moons formed after a celestial body collided with Mars. The "capture" hypothesis says they are asteroids pulled in by Mars's gravity. Settling the question would help reveal, in Jaxa's words, "how a habitable environment for life might have arisen on the terrestrial planets", meaning Mercury, Venus, Earth and Mars. Nasa said MMX's findings will also help shape future Mars missions, including crewed expeditions.

The launch also sits in a wider race. The article describes the US and China as competing to be first to return rock samples from the surface of Mars. Nasa's Perseverance rover, on Mars since 2021, has already collected samples, but their return to Earth was halted by the Trump administration after a congressional vote in January this year. China's Tianwen-3 is scheduled to launch around 2028 and could bring back Mars samples as early as 2031, potentially before the Japanese mission's return.

Key facts

MMX launched on Japan's H3 rocket at 4:41am from Tanegashima, and Jaxa declared success when the spacecraft separated from the upper stage about an hour later.
The target is at least 10g of soil and rock from Phobos, with arrival in Mars orbit in August next year and a sample return scheduled for 2031.
A small French-German rover, Idefix, will survey the surface for 100 days; the lander will then spend only two hours on Phobos collecting material.
The $578m, five-year mission involves five space agencies and is the first attempt to land on Phobos or Deimos.
The samples should help decide between the "giant impact" and "capture" hypotheses for how the Martian moons formed.

Why it matters

No one has tried to land on Phobos or Deimos before, and MMX would be the first sample return from the Martian system. The origin of the two moons is unsettled: either a body hit Mars and the debris formed them ("giant impact"), or Mars pulled in passing asteroids ("capture"). Jaxa says the answer will help show how a habitable environment might have arisen on the terrestrial planets. Nasa adds that the findings will inform future Mars missions, including crewed ones.

Who it affects

Planetary scientists who study how Mars and its moons formed are the direct audience, along with the five collaborating agencies. The article names Jaxa, Nasa, the Germany Space Agency and a French-German rover. Nasa astrophysicist Tom Statler is involved in the project. Planners of future Mars missions, including crewed expeditions, are also affected, since Nasa says MMX's findings will help shape them.

How to use it

This is a mission to follow rather than a product to use. The milestones in the report are: arrival in Mars orbit in August next year, Idefix's deployment and its 100-day survey of Phobos, the lander's two-hour sampling stop, Deimos flybys, departure from Mars's orbit in November 2030, and the return to Earth in 2031.

How solid is it

The launch itself is reported as done: liftoff at 4:41am and a successful separation from the upper stage, as declared by Jaxa scientists. The schedule (August arrival, November 2030 departure, 2031 return) comes from Jaxa and officials and is a plan, not an outcome. The report gives the $578m cost without a breakdown. It does not name the five collaborating agencies.

Risks and caveats

A successful launch does not mean the mission is secured; arrival, landing and sampling are all still ahead. The margins are tight: the rover is expected to bounce for several minutes in Phobos's very weak gravity, if all goes according to plan, and the lander has only two hours on the surface. Competition is a factor too. Tianwen-3 could bring back Mars samples as early as 2031, potentially before MMX returns, and the return of Perseverance's samples was halted by the Trump administration after a congressional vote in January this year.

“It is a once-in-a-lifetime chance. We are part of the first sample return mission from the Martian system”

— Markus Grebenstein, the Germany Space Agency's rover chief