A robotic spacecraft and rover are heading to Phobos to gather the first pristine soil samples from the Martian system.
A Japanese spacecraft blasted off from the Tanegashima Space Center before dawn on Tuesday on an international mission to explore Mars’ moons and bring soil samples back to Earth. According to PBS NewsHour, the Japan Aerospace Exploration Agency is leading the $578 million Martian Moons Exploration mission, known as MMX, alongside space agencies from the United States, France, Germany and Europe.
If the five-ton spacecraft succeeds, it will deliver the first samples ever gathered from the Martian system, BBC News reported. The probe carries a four-wheeled rover to explore the surface before a stationary lander touches down to vacuum and drill up moondust for a planned return in 2031.
Why the mission matters
Scientists want to inspect the moon’s material to solve an enduring debate over how Mars got its two moons, Phobos and Deimos, about 4.5 billion years ago. As Wired reported, researchers have two primary hypotheses: either the moons are rocky debris thrown into orbit after a massive collision with Mars, or they are stray asteroids pulled in by the planet’s gravitational pull.
MMX carries an instrument called MEGANE, developed with Johns Hopkins University, which will measure gamma rays and neutrino particles emitted by Phobos to check for volatile elements like potassium and hydrogen. Higher levels of volatiles would suggest a captured asteroid, while lower levels would point toward an impact.
Laboratories on Earth will also search the returned soil for grains of Mars itself. Because Phobos orbits close to Mars, impacts on the Martian surface frequently throw rock fragments onto the moon. Scientists currently have only rare Martian meteorites on Earth, which suffer contamination from terrestrial air, dust and water as soon as they land. Pristine samples from Phobos would give researchers uncontaminated evidence about the makeup and history of Mars.
Previous attempts and background
No agency has ever landed on Phobos or Deimos. The moons carry the names of the Greek gods of fear and dread, and past efforts to reach them have met with disaster. Russia sent three probes toward Phobos starting in the 1980s, but all three failed. Japan also failed to place a probe into orbit around Mars during its only prior trip to the red planet.
Japan brings significant experience with small-body sample returns to the new effort. JAXA’s Hayabusa probe collected particles from asteroid Itokawa in 2010, and Hayabusa2 delivered material from asteroid Ryugu in 2020. However, team members pointed out that Phobos presents different gravitational forces and orbital dynamics than those asteroids.
Other Mars sample initiatives have faced delays and cancellations. While NASA’s Perseverance rover has collected samples into tubes since arriving on Mars in 2021, a planned joint American and European mission to retrieve those containers was effectively canceled after the U.S. Congress halted its funding. NASA is still weighing options to bring those tubes back.
What happens next
The spacecraft faces a long flight before reaching its target. S1 reported the craft is scheduled to arrive at Phobos in August 2027, while S2 reported it will reach Mars by late next summer.
Once in orbit, the mother ship will release a microwave-sized rover named Idefix, built by French and German space agencies. Because Phobos has very low surface gravity and is tugged by Mars’ stronger gravity, the rover will drop onto the surface, bounce for several minutes and right itself before moving at 1 millimeter per second. Over 100 days, Idefix will scout safe landing locations to protect the mothership from soft soil and jagged rocks.
In late 2028 or 2029, the mothership lander will touch down for about two hours. It will deploy two different collection tools and a robotic arm to capture at least 10 grams of dust and pebbles. The craft will then conduct flybys of Deimos before leaving the Martian system in 2030.
A return capsule is scheduled to land in the Woomera desert of South Australia in 2031. China is also preparing a Mars sample return mission, aiming to launch in 2028 and return material in 2031.
