JAXA’S MMX Mars Mission Readies for Launch with Two NASA Instruments

The Japan Aerospace Exploration Agency (JAXA) is getting ready to launch its Martian Moons eXploration mission early next week. The spacecraft will collect samples of Phobos, one of the moons of Mars, and return them to Earth in 2031. Today NASA highlighted its role in the MMX mission, including two scientific instruments, MEGANE and P-Sampler, that will help determine whether Phobos and its companion, Deimos, are captured asteroids or remnants of a collision.

MMX is JAXA’s third sample return mission. Hayabusa brought back 1,500 particles of asteroid Itokawa in 2010, followed by Hayabusa2 that delivered 5.4 grams (0.2 ounces) from asteroid Ryugu in 2020.

NASA also has experience in returning samples from other worlds. In addition to the 382 kilograms (842 pounds) of Moon rocks brought back by Apollo astronauts, NASA completed its own asteroid sample return mission in 2023 with  OSIRIS-REx bringing back 121.6 grams (4.29 ounces) of material from Bennu. In addition, samples of the solar wind were retrieved on the Genesis mission and dust from a comet on Stardust.

The two countries cooperate extensively on both space science and human spaceflight missions. MMX is another example and also includes France’s CNES, Germany’s DLR, ESA, and the government of Australia, where MMX’s sample container will land.

MMX will study both Phobos and Deimos, but the primary focus is the larger of the two, Phobos, 22 km (14 mi) in diameter compared to 12 km (7.5 mi) for Deimos.

The origin of the two moons is a mystery. Some scientists think they are asteroids captured by Mars’s gravity, while others are convinced they are remnants of a collision between Mars and another object. Studies of the samples MMX returns to Earth hopefully will answer that question and aid our understanding of how the solar system formed.

Launch on Japan’s H3 rocket from Tanegashima is scheduled for 4:41 am Japan Standard Time on Tuesday, October 20 (3:31 pm Monday, October 19, EDT). During today’s briefing, NASA Planetary Science Division Acting Director Lindsay Hays said MMX will arrive at Mars in August 2027, with sample collection no earlier than December 2028 and return to Earth in 2031.

NASA is contributing two science instruments: the Mars-moon Exploration with GAmma rays and NEutrons (MEGANE) spectroscopy instrument developed by the Johns Hopkins University Applied Physics Lab (APL), and the Pneumatic collection mechanism (P-Sampler) from Honeybee Robotics, part of Blue Origin.

MEGANE (meh-GAH-nay) will study Phobos as MMX flies close to the surface to measure the moon’s elemental composition using gamma-ray neutron spectroscopy. The technique has been used already to study our Moon, Mars, Mercury and asteroids. By coincidence, megane means eyeglasses in Japanese. APL Principal Investigator David Lawrence said they like to think of MEGANE as an instrument that looks at Phobos with gamma ray and neutron glasses.

MMX will not just orbit Phobos, but land on it, dropping a rover — Idefix, developed by DLR and CNES — as it descends.

Honeybee Robotics’ P-sampler is on one of the landing legs to collect samples of the surface. Kris Zacny, the company’s vice president, said it will happen in a matter of seconds. “You blink, and it’s all done.” P-sampler has been tested already in the Mojave desert on Earth, and on the Moon during Firefly’s Blue Ghost Mission-1 in 2025 when it collected 13 grams of lunar regolith.

In addition to the two instruments, NASA is providing communications support through the Deep Space Network. Hays said the 14-year life cycle cost to NASA through the end of the mission is $87 million. NASA will receive “at least 15 percent” of the samples for analysis and “long-term curation for future research to answer the questions we don’t even know yet how to ask.”

Indeed, answering that question about the origin of the moons may not be easy. Tom Statler, MMX program executive and scientist at NASA headquarters, said Phobos and Deimos look like D-class asteroids found elsewhere in the solar system, but their orbits are circular and aligned with Mars’s equator, not tilted.

“If you had things coming from outside being captured, they wouldn’t necessarly align up that way with the equator of Mars.” Conversely, “a giant impact on the surface of Mars, that blasts material up” could cause the material to settle into a disk and “the moons agglomerate out of that.”

“So you see, there’s two totally different lines of evidence that point in two different directions. That’s what makes it an interesting puzzle.” — Tom Statler, NASA