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Japan on Monday launched an ambitious $350 million mission to Mars to study the red planet’s two moons in unprecedented detail, dropping a small rover on the largest – Phobos – before touching down on the mothership to collect soil samples to return to Earth.
The main goal of the Martian Moons Exploration Mission, or MMX, is to determine whether Phobos and the smaller moon Deimos were created by the impact of a large body early in the solar system’s history, or whether the two are asteroids that once passed close enough to Mars to be captured by the red planet’s gravity.
The Martian moons are much smaller than Earth, Phobos measuring just 17 miles across at its widest, while Deimos is less than half the size. Both are irregularly shaped and similar to asteroids. But size and shape alone are not enough to answer the question of their origin.
“One of the most interesting questions about Phobos and Deimos is simply why these two small moons are there in the first place,” said Thomas Statler, who helped oversee the development of two NASA instruments aboard the MMX spacecraft.
“In some ways they resemble asteroids from the outer part of the asteroid belt … but there (are) other lines of evidence that point to these moons being remnants of a giant impact early in Mars’ history.”
Jack
The collected samples, which are expected to return to Earth in 2031, should answer that question one way or another.
“By visiting the Martian moons, studying them closely and bringing samples back to Earth, we can determine whether Phobos’ material is more consistent with an asteroid composition or with debris resulting from a collision with Mars,” Statler said.
The mission will begin at 3:41 p.m. EDT (4:41 a.m. Japan time) with the sky-lighting launch of a Japanese H3 rocket from the picturesque Tanegashima Space Center operated by the Japan Aerospace Exploration Agency, or JAXA.
Four solid-propellant strap-on boosters and two hydrogen-fueled first-stage engines propelled the rocket from the dense lower atmosphere before the H3’s second stage took over to continue the climb into space.
NASA
One hour and 11 minutes after liftoff, after two upper stage engine fires, the 9,900-pound MMX probe was released to fly alone.
If all goes well, the spacecraft will break into orbit around the Red Planet in September 2027 on a path that will allow it to circle the planet in lockstep with Phobos.
MMX will spend three years in that orbit, training a battery of instruments on Phobos and its surroundings, studying its chemical and mineral composition, assessing its possible use as a staging base for future astronauts and dropping a small rover, supplied by the German and French space agencies, to the lunar surface in early 2029.
The 55-pound rover is not equipped with brake missiles or anything else to slow its descent. Because Phobos’ gravity is only 1/1,000th as strong as Earth’s, the rover is expected to bounce to the surface, and gently spin to a stop.
It is designed to right itself regardless of how it ends up after coming to rest and then starting its surface exploration. It is equipped with cameras for navigation and to study the soil as it rolls, an instrument to shoot laser beams into the soil to determine what minerals are present and another to monitor soil temperatures.
JAXA
About a year after the rover’s landing, in the 2030 time frame, the MMX spacecraft itself will touch down on Phobos once and possibly twice to collect a small amount of soil with two instruments, one built by JAXA and the other provided by NASA.
The official mission requirement is to capture at least 10 grams, or less than half an ounce, of material. However, depending on the nature of the soil, the sample size may be larger.
MMX will then lift off and, after completing remote observations of Deimos, return to Earth, placing Phobos samples in an aerodynamic, heat-resistant capsule that will re-enter the atmosphere over Australia, where a recovery team will be stationed.
The samples are studied by an international team of researchers.
“There’s a lot of adrenaline, a lot of excitement and a lot of wow,” Statler said. “MMX will be the first spacecraft to return to Earth from the Mars system. That’s saying a lot.”
But “the most exciting thing of all,” he said, “will be the sample reentry capsule re-entering the Earth’s atmosphere and opening this capsule and seeing these materials for the first time. There is absolutely no shortage of excitement and adrenaline on this mission.”
