JAXA launches Martian Moons eXploration mission to retrieve first samples from Mars system

The MMX spacecraft will orbit Mars, land on Phobos, and return at least 10 grams of regolith to Earth by 2031, aiming to resolve the moons' mysterious origins.

By LineZotpaper

Published20 October 2026

Read Time3 min

Japan Aerospace Exploration Agency’s (JAXA) Martian Moons eXploration (MMX) mission successfully launched from the Tanegashima Space Center on October 20, 2026, beginning a journey to Mars and its largest moon, Phobos, with arrival at Mars expected in August 2027. The mission aims to collect and return the first-ever samples from the Martian system, potentially settling a long-running debate over whether Phobos and Deimos are captured asteroids or remnants of a giant impact on Mars.

The MMX spacecraft lifted off at 04:41 JST and separated from its launch vehicle 17 minutes later. It is now on course to reach Mars in August 2027, where it will enter orbit around the planet before transferring to an orbit around Phobos about a month later.

The mission consists of an orbiter and a small lander called Idefix, developed by Germany and France. Idefix will be dropped onto the Phobos surface from between 40 and 100 meters altitude, the moon’s weak gravity means the rover will simply right itself and begin science operations. It will help identify a suitable landing site for the main sample collection phase.

In 2030, the orbiter will land on Phobos, either once or twice, and collect at least 10 grams of regolith. After collection, MMX will perform flybys of Mars’ other moon, Deimos, before returning to Earth. The sample return capsule will separate from the mission’s Return Module and land at the Woomera Prohibited Area in South Australia, while the Return Module burns up in the atmosphere. The samples are expected to arrive on Earth in 2031.

The origins of Phobos and Deimos remain a vigorous debate in planetary science. One leading theory holds that a giant impact on Mars early in the Solar System created a debris ring from which both moons formed. Another suggests both are captured asteroids. A third possibility is that Mars captured a single asteroid that was shredded by gravity into a ring, with both moons forming from that debris. A more complex scenario involves a massive impact, a large moon, and a retinue of smaller moons that eventually crashed back into the planet, leaving only Phobos and Deimos.

A sample of just 10 grams of Phobos regolith, combined with MMX’s remote sensing data, could resolve the debate. If the material matches Mars’ mineralogy and isotopic composition, it supports the giant impact scenario. If it matches asteroidal material, it supports the capture theory. A hybrid result would indicate a partial capture or complex formation process.

JAXA has a strong track record with sample returns: Hayabusa brought back material from asteroid Itokawa in 2010, and Hayabusa2 returned samples from asteroid Ryugu in 2020. The agency’s experience suggests a high probability of success for MMX.

Analysis

Why This Matters

First sample from the Martian system: If successful, MMX will return the first physical material from Mars’ moons, providing direct data to test competing formation theories that have puzzled scientists for decades.
Understanding planetary evolution: The origin of Phobos and Deimos carries implications for how Mars evolved, including its early impact history and the role of moon formation in planetary systems.
Sample return expertise: JAXA’s previous successes with Hayabusa missions demonstrate that sample return from small bodies is achievable, strengthening the case for future Mars sample return efforts.

Background

Mars has two small irregular moons, Phobos and Deimos, discovered in 1877. Their composition appears different from Mars’ surface, which suggests they may not be native debris from a giant impact. However, their near-circular orbits close to the Martian equator make two independent asteroid captures unlikely. Both moons are key targets for understanding Mars’ early history. JAXA’s Hayabusa and Hayabusa2 missions returned samples from near-Earth asteroids, establishing the agency’s capability for complex sample-return missions. MMX is the first mission dedicated to retrieving material from the Martian system.

Key Perspectives

Planetary scientists: The MMX sample could settle the impact-versus-capture debate. A sample matching Mars’ composition strongly supports the giant impact theory; asteroidal material supports capture. Even a surprise finding would greatly advance knowledge. Asteroid-capture theorists: They note that Phobos and Deimos appear compositionally different from Mars, favouring the capture hypothesis. The near-equatorial orbits could be explained by a single captured asteroid that broke up, or by orbital migration. Impact-theory advocates: They argue that the circular, near-equatorial orbits are better explained by a debris ring from a giant impact. The low probability of two simultaneous captures makes the impact scenario more plausible despite the compositional discrepancy.

What to Watch

August 2027 arrival at Mars: The critical Mars orbit insertion will determine the mission’s fate.
Idefix deployment in 2027-2028: Successful landing and operations will validate the landing approach for the main sample collection.
2030 Phobos landing and sample collection: Two landing attempts may be required to secure at least 10 grams of regolith.
2031 sample return capsule landing: The capsule’s arrival at Woomera will mark the mission’s success or failure.

Sources

JAXA's Martian Moons eXploration Mission is on its Way to Mars and Phobos · Universe Today

Checked

11 claims in this story checked against 1 source: 7 supported.

Show each claim

SupportedJAXA has launched MMX on a mission to retrieve the first samples from the Mars system.Universe Today: “JAXA, the Japan Aerospace Exploration Agency, has finally launched its Martian Moons eXploration (MMX) mission.”
Partly supportedMMX will return at least 10 grams of regolith.Universe Today: “The goal is to collect at least 10 grams of material.”
SupportedThe MMX spacecraft will orbit Mars before landing on Phobos.Universe Today: “MMX will reach Mars in August 2027 and enter an orbit around the planet. After about one month, it will transfer to an orbit around Phobos.”
Partly supportedThe samples will arrive on Earth by 2031.Universe Today: “The sample, if collected successfully, should be back on Earth in 2031.”
SupportedMMX launched from Tanegashima on October 20, 2026, at 04:41 JST and separated from its launch vehicle 17 minutes later.Universe Today: “The launch occurred at 04:41:03 JST on October 20, 2026 from the Tanegashima Space Center, Japan's primary spaceport. 17 minutes after lift-off, MMX separated from its launch vehicle”
SupportedMMX is due to reach Mars in August 2027 and transfer to an orbit around Phobos about a month later.Universe Today: “MMX will reach Mars in August 2027 and enter an orbit around the planet. After about one month, it will transfer to an orbit around Phobos.”
SupportedIdefix will be dropped onto Phobos from 40 to 100 metres above its surface, right itself, and begin science operations.Universe Today: “Idefix will simply be dropped onto the surface of Phobos from between 40 and 100 meters above. The small moon's gravity is so weak that the rover won't be damaged. Regardless of how it lands, it will right itself and get to work.”
Partly supportedIn 2030, MMX will land on Phobos once or twice and collect at least 10 grams of regolith.Universe Today: “In 2030, MMX will then land on Phobos, either once or twice, and collect regolith samples. The goal is to collect at least 10 grams of material.”
SupportedThe sample capsule will be sent to Woomera in South Australia, while the Return Module burns up in Earth's atmosphere.Universe Today: “The capsule containing the samples will separate from the Return Module and be sent to the Woomera Prohibited Area in South Australia to be retrieved, while the Return Module will burn up in Earth's atmosphere.”
Partly supportedA hybrid sample result would indicate partial capture or a complex formation process.Universe Today: “In the partial capture or hybrid scenario, the sample material should be asteroid-like, but have some differences in bulk composition and volatile content.”
SupportedJAXA's sample-return experience suggests a high probability of success for MMX.Universe Today: “Their track record suggests that MMX will be successful, too.”

Correction

20 October 2026An earlier version of this story said MMX's journey to Mars and Phobos would take five years. MMX is expected to reach Mars in August 2027, with samples expected to return to Earth in 2031.