Japan launched a spacecraft toward Mars today (20 October) on an unprecedented mission to explore the planet's mysterious moons and bring samples back to Earth.
Five of the world's space agencies have joined forces for the five-year mission, which will attempt to land a robotic lander and a rover on Phobos, the larger and closer of Mars' two small moons.
The Japan Aerospace Exploration Agency (JAXA), which is leading the sample-return mission, launched the spacecraft before dawn from the country's main spaceport on Tanegashima Island. Officials declared the launch successful about an hour later after the spacecraft separated from the rocket's upper stage as planned.
Flight controllers erupted in applause, rose to their feet and exchanged handshakes and embraces.
Although NASA has successfully landed nine spacecraft on Mars over the past five decades and China achieved a landing in 2021, no spacecraft has ever landed on Phobos or its companion moon, Deimos. No one has yet brought samples back from Mars or either of its moons.
If successful, the mission will deliver dust, soil and rock samples from Phobos to Earth in 2031.
"There's a lot of adrenaline and a lot of excitement and a lot of wow," said NASA astrophysicist Tom Statler, who is involved in the project.
Japan has an advantage in the mission, having already completed two successful asteroid sample-return missions.
Phobos: A small, potato-shaped moon
Phobos is an irregular, potato-shaped rocky body measuring about 14 miles (22 kilometres) across. Scientists hope that examining samples from the moon will help explain how Mars' moons, and potentially moons elsewhere in the solar system, formed.
Known as Martian Moons Exploration (MMX), the $578 million mission features a five-tonne spacecraft expected to reach Mars by late next summer.
The spacecraft will align itself with Phobos' close orbit around the Red Planet before deploying a French-German rover named Idefix, after the white terrier in the Asterix comic series.
About the size of a microwave oven, Idefix will land on Phobos independently, bouncing for several minutes before coming to a stop in the moon's extremely weak gravity.
What happens after the rover lands?
The four-wheeled rover is designed to turn itself upright if it lands upside down. However, it could become stuck if it sinks into soft soil or gets trapped between rocks, said Julien Baroukh of the French Space Agency.
Once its solar panels are deployed, the rover will no longer be able to right itself, he said. This is why it will move at an extremely slow speed of one millimetre per second (0.04 inches per second).
According to Baroukh, Idefix will act as a "scout for safety" as it explores Phobos for 100 days. Japanese flight controllers aim to identify areas free of powdery soil and difficult terrain before the main spacecraft's four-legged stationary lander descends to collect samples in late 2028 or 2029.
The lander will remain on Phobos for only two hours, drilling into the surface and vacuuming up at least one-third of an ounce (10 grammes) of material before launching back into space.
The spacecraft will also study Deimos through a series of flybys before leaving the Martian region in 2030 and returning to Earth with the samples in 2031. The sample capsule is expected to land in the Australian desert.
The mission faces considerable risks, with previous spacecraft failures highlighting the challenges of exploring the Martian moons.
The names of the moons reflect their ominous associations: Phobos means fear in Greek, while Deimos means dread. In Greek mythology, they are the twin sons of Ares, the god of war, known as Mars in Roman mythology.
Scientists hope to uncover how Mars' moons formed
Russia has failed in all three of its attempts to explore Phobos, as well as in several other Mars missions. Japan also previously failed to place a spacecraft into orbit around Mars during its only other mission to the planet.
Even NASA has experienced setbacks in its efforts to answer a fundamental question: whether life ever existed on Mars.
By examining the moons, scientists hope to determine whether Phobos and Deimos formed following an ancient collision between Mars and a large space rock. Another possibility is that they are asteroids captured by Mars' gravitational pull.
Regardless of their origin, scientists expect Phobos to contain traces of Mars itself. This could make the samples especially valuable, offering insights into the formation of planets and moons and potentially the origins of life.
The findings are also expected to help shape future Mars exploration missions, including those involving astronauts, said Lindsay Hays, NASA's acting planetary science director.
"It is a once-in-a-lifetime chance. We are part of the first sample return mission from the Martian system," said Markus Grebenstein, the rover chief at the German Space Agency.
Japan is not alone in pursuing the scientific opportunities offered by the Martian system. China plans to launch its own Mars sample-return mission in 2028, while NASA is still debating how to retrieve more than 30 sample tubes collected by its Perseverance rover, which currently holds the record for driving the longest distance on another world.
Japan and China could be competing closely to bring back samples from the Martian system, with both countries targeting 2031 for their return.
Japan is contributing $350 million to the MMX mission. NASA is providing $87 million, while the French Space Agency is contributing about $68 million, the German Space Agency around $56 million and the European Space Agency approximately $17 million.