The MMX probe set off on a historic mission directed towards Phobos with the aim of bringing a soil sample back to Earth: around ten grams of dust which will serve to clarify the origin of the Mars satellites.
At 9.41pm Italian time on October 19, an H3 rocket lifted off from the Tanegashima Space Center, Japan, carrying the MMX (Martian Moons eXploration) probe.
The H3 launcher departed as scheduled and, approximately 71 minutes and 13 seconds after liftoff, the separation of the MMX spacecraft was confirmed. The MMX probe was then placed into the pre-established orbit
It is the first mission to take a sample from a Martian moon and bring it back to Earth. The loot will be modest: around ten grams of material. But the questions that that material can clarify are anything but small: here they are…
Where did Phobos and Deimos come from?
It is the question that gave rise to the mission. The two moons are tiny and irregular, so much so that they look more like cosmic stones than the round satellites of the giant planets. For decades, astronomers have been divided between two explanations: asteroids captured by Martian gravity, or fragments born from a gigantic impact, re-aggregated in orbit.
Each explains something and leaves something else out. The champion will serve as judge. An asteroid-type composition, primitive and rich in volatile compounds, would tip the balance towards capture. Reworked material, closer to Martian rocks, would indicate a local origin. As JAXA wrote, understanding how Mars and its moons formed is one of the most hotly debated topics in Solar System science.
What’s inside a “piece of Mars” brought from space?
Phobos orbits very close to the planet and over billions of years has collected some of the material thrown up by impacts on the Martian surface. Its soil could therefore contain, mixed with its own, grains arriving from Mars itself.
It would be an indirect and relatively cheap way to get our hands on Martian material, while other sample return programs are struggling.
Is this a possible mission? The technical challenge
On paper the route is well mapped out. According to plans, the probe will enter orbit around Mars in August 2027 and around Phobos in September of the same year. Then the release of a small rover and sampling will follow: two types of sample, on two different sides of the moon. The return is planned in two stages: the reentry module will leave Mars in November 2030 and the capsule will land in 2031 in the Woomera area, Australia. Also traveling on board is a small European guest: the IDEFIX rover, about 25 kilos here on Earth, developed by CNES and DLR and the first non-Japanese rover on a body other than our Planet. It will have to move where gravity is very weak and the surface is little known.
Landing on Phobos is unlike any landing made so far and the precedent to avoid is that of Philae, the lander of the Rosetta mission, which in 2014 bounced off comet 67P after the docking failure. On Phobos, gravity is so weak that the 25 kg of IDEFIX will weigh just 12 grams, like a grape.
The rover will not actively brake: it will be released from about 40 meters above sea level and will touch the ground at about 1 meter per second, well below the moon’s escape velocity of about 10 m/s, so as not to be bounced back into space. The rover’s designer at DLR, Markus Grebenstein, explained that the fall lasts 60 to 80 seconds and the impact occurs at less than one meter per second. The bounces, however, are taken into account: IDEFIX will stop in a random point after a few bounces, then it will right itself and open the solar panels, all autonomously.
