Japan's probe is off to Mars, moonlighting for a sample

Japan launched its MMX spacecraft toward Mars on October 20, Japan time, and it separated cleanly from its rocket, starting a five-year effort to bring back soil from the Martian moon Phobos.

The launch came from the Tanegashima Space Center on an H3 rocket. The rocket's upper stage released the spacecraft after the burn that sends it out of Earth's orbit toward Mars, and the separation was reported as successful. ^[1][3] The mission is led by the Japan Aerospace Exploration Agency (JAXA), with partners from other countries.

Sample-return missions beyond the Moon are rare, and this one aims at a target no one has brought home before. Mars has two moons, Phobos and Deimos, and nobody knows where they came from. The Daily Inference reported on Friday that the material could show whether they are captured asteroids or debris from an ancient impact. That question is now a spacecraft in flight.

A room that finally exhaled

The launch report describes mission-control staff applauding and embracing once the spacecraft was away. ^[1] Tom Statler, a NASA astrophysicist involved in the project, put the mood in a sentence: "There's a lot of adrenaline and a lot of excitement and a lot of wow." ^[1]

The celebration is for a first step. Separation on the right trajectory is the easiest of MMX's milestones to count and the shortest to reach. Everything after it is a plan, and JAXA's own schedule page notes that schedules can change.

What MMX is meant to do

The name stands for Martian Moons eXploration. The spacecraft is due to reach Mars in August 2027, according to NASA, and Space.com describes the transit as about 10 months. ^[2][3]

Once there, MMX will survey Phobos before it tries to land. A French-German rover named Idefix is part of the mission. It is meant to scout the terrain ahead of the lander, with deployment planned for late 2028 or early 2029. ^[1][3]

Then comes the hard part. The lander is expected to gather at least 10 grams of Phobos material during a brief stay on the surface, in late 2028 or 2029. NASA says sampling will come no earlier than December 2028. ^[1][2] Ten grams is about the weight of ten paperclips. For rock and dust from another world's moon, it is a lot.

Two tools will do the collecting. JAXA's C-Sampler is designed to extract material from a few inches below the surface. NASA contributes a second, the P-Sampler, which is powered by nitrogen gas. ^[2] Having two systems is a sensible hedge on a surface no lander has touched.

After Phobos, MMX is planned to fly past Deimos, then leave the Martian system in 2030 and send its capsule back to Earth in 2031. ^[1][3]

Two stories about two moons

Scientists are weighing two main explanations. In one, a large impact on Mars threw material into orbit, and that debris gathered into the moons. In the other, the moons are asteroids that wandered close and were caught by Mars's gravity. ^[1][2]

The two stories predict different things about the rock. Debris from Mars should look like Mars. A captured asteroid should look like something that formed elsewhere. From a distance, the question has not been settled. A sample in a laboratory on Earth could do it, and MMX is built to deliver one.

NASA's instrument will help even before any sample comes home. Its MEGANE instrument will measure neutrons and gamma rays coming off Phobos, which reveal the elements in the surface. ^[2] That gives the team a composition map to plan the landing and to check against the sample later.

Why the answer reaches beyond Mars

The origin of two small moons might sound like a niche problem. Statler argues it is not. Resolving it could illuminate an early era when Earth and the other inner planets may have acquired much of their water and organic compounds. ^[2]

It means these moons are possible witnesses to the period when planets like ours were stocked with the ingredients for oceans and, eventually, life. Whether the moons are Martian wreckage or visitors from the asteroid population, the sample would be a record from that time.

NASA is a significant partner. It supplies MEGANE and the P-Sampler, plus communications and navigation support and researchers. It also expects to receive and curate about 15 percent of the returned sample at the Astromaterials Lab at its Johnson Space Center. ^[2]

If the lander collects only the 10-gram minimum, that share would be about 1.5 grams. The rest is for Japan and other partners.

What is not known yet

The science is still ahead. No result about the moons' origin exists, and no Phobos material will be in a laboratory before 2031. ^[1][2] Whether the schedule holds, and whether the survey finds a safe place to land, are questions the next two years will answer.

The next milestone is the arrival at Mars in August 2027. The landing and sampling attempt follows no earlier than December 2028. ^[2]