Japan launches mission to bring home a piece of the Martian moon Phobos - Ars Technica

Japan launched a $578 million mission Monday on a five-year expedition to land on the largest moon of Mars and retrieve samples for return to Earth, a daring international project that could yield new insights into the formation of the Solar System.

The robotic Martian Moons eXploration mission, known as MMX, lifted off at 3:41 pm EDT Monday (4:41 am Japan Standard Time Tuesday) from Tanegashima Space Center in southern Japan.

The MMX spacecraft rode into orbit atop a 207-foot-tall (63-meter) H3 rocket, Japan’s flagship launch vehicle. The rocket assigned to MMX debuted a new souped-up configuration with four strap-on solid rocket boosters, full-throttle main engines, and an extended payload shroud to accommodate the demands of Japan’s heaviest and most ambitious interplanetary mission to date.

The rocket’s upper stage accelerated the MMX spacecraft to a top speed of more than 24,000 mph, fast enough to break free of Earth’s gravitational pull for the 10-month voyage to Mars. The nearly 9,900-pound (4.5-metric ton) spacecraft — two-thirds of its mass comprised of propellant — separated from the H3 rocket about 71 minutes after liftoff.

Hiroshi Yamakawa, president of the Japan Aerospace Exploration Agency (JAXA), declared the launch a success. “A long journey of five years has just started,” Yamakawa said.

MMX established contact with ground controllers, unfurled its solar panels, and was in a “very stable condition” soon after separating from the H3 rocket, according to Yasuhiro Kawakatsu, the mission’s project manager at JAXA. “So far, so good.”

“The MMX [mission] we launched today is a challenging mission aiming for the world’s first sample return from the Martian moons,” said Yoshihiro Seki, Japan’s science minister. “We hope that the results obtained through this mission will contribute to the development of our nation’s space science and exploration technology.”

The mission to the Martian moons builds on Japan’s success in leading the Hayabusa and Hayabusa 2 missions, the world’s first two spacecraft to bring back pristine specimens from asteroids. Scientists believe Phobos could itself be an asteroid that was captured into orbit around Mars billions of years ago. One of MMX’s science goals is finding out if that theory is correct.

With the Hayabusa missions, sample returns from deep space have become a “speciality” for Japan’s space program, Kawakatsu said. For MMX, Japan attracted contributions from NASA and space agencies in Europe.

“We have a proven track record of success in these areas,” Kawakatsu said. “Because of this, I believe they are participating with the understanding that if they want to conduct celestial body sample returns, joining a mission led by Japan is more certain to succeed than the US or Europe launching their own missions.”

MMX will spend about three years in the vicinity of Mars after arriving there next August, conducting a series of encounters with the Martian moons Phobos and Deimos. Phobos is the larger of the two, with a lumpy, potato-like shape, an average diameter of 14 miles (22 kilometers), and a surface area comparable to the city of Houston.

Upon reaching Mars, MMX will jettison its propulsion module, dead weight after burning all its fuel to enter orbit around the red planet. That will leave the main section of the MMX spacecraft and its four-legged landing gear, known as the exploration module, to move closer to Phobos.

The moon’s gravity is too weak and the pull of Martian gravity too strong for the MMX spacecraft to enter a stable orbit around Phobos. Instead, the spacecraft will fly in a so-called quasi-satellite orbit, remaining bound to Mars while still able to maneuver around Phobos.

The mission’s reconnaissance of Phobos will culminate in late 2028 or early 2029, when the MMX mothership will release a small rover to drop onto Phobos. The four-wheeled robot, named Idefix, is a contribution from the French and German space agencies. Idefix, the size of a large shoebox, will attempt to drive around Phobos for up to 100 days while grappling with the moon’s rough topography and tenuous gravity, less than one-thousandth that of Earth’s.

The climax for MMX will come later in 2029, when the main spacecraft will attempt up to two landings on Phobos. The probe’s landing gear is designed to absorb the energy of each landing to mitigate the risk of tipping over or bouncing back into space, a real concern with the feeble and uneven gravity field on Phobos.