Why are the two moons of Mars wo tiny and irregularly shaped? And how did they come about? The international MMX mission should clarify these questions from 2024. For the first time, a space probe will set down a rover and a sample recovery module on the Martian moon Phobos. Essential parts of the rover have now been completed at the German Aerospace Center. They should enable the vehicle to withstand a fall from a height of 50 meters without damage and to drive in minimal gravity without floating away.

The Mars moons Phobos and Deimos have been a mystery since their discovery in 1877. Because with only 15 and 27 kilometers in diameter and an irregular shape, they resemble captured asteroids more than moons. At the same time, however, they orbit Mars very closely and in the equatorial plane, which does not fit the capture scenario. Some planetary researchers therefore suspect that Mars used to have a ring from the remains of which the moons were formed.

The MMX space probe should solve the mystery of the moons of Mars in the near future. The mission, carried out by the Japanese space agency JAXA together with NASA, ESA, the French space agency CNES and the German Aerospace Center (DLR), will launch in 2024 to the Martian moons. It consists of three modules: the propulsion module, a landing module with the MMX rover and a return module with the capsule for sample return.

The MMX spacecraft will first study the two moons of Mars from an orbit around Mars. It will then swing into a quasi-orbit around the Martian moon Phobos, collect data there, set down the MMX rover it is carrying and take samples from the lunar surface. After sampling, the spacecraft returns to Earth with the material collected on Phobos. The MMX rover is scheduled to land on Phobos in 2027 and return to Earth with the samples in 2029.

DLR and CNES are contributing the MMX Rover, which weighs around 25 kilograms, to the mission. “With the MMX Rover, we are breaking new technical ground, because never before has a wheeled reconnaissance vehicle driven on a small celestial body that only has around one-thousandth the force of gravity,” says Markus Grebenstein from the DLR Institute of Robotics and Mechatronics in Oberpfaffenhofen.

In order to maintain ground contact despite this minimal gravity, the rover can only drive very carefully, at a few millimeters per second. With the help of two wheel cameras, he will keep an eye on the wheels and the ground and at the same time collect data on the Phobos surface. An infrared radiometer and a Raman spectroscope provide further information about the mineral composition and the porosity of the Martian moon.

Another challenge: having arrived at the Mars moon Phobos, the MMX rover will be separated from the MMX mother probe and free fall about 50 meters to the lunar surface. It must therefore be robust and at the same time flexible enough to survive this in a functional manner. This is to be ensured by a stable Rover chassis including a carbon structure and a special erecting structure.

“Because the rover is in free fall from the spacecraft on Phobos, it will do several somersaults on landing and come to rest in an unpredictable position,” explains Grebenstein. “From this situation, it has to stand up autonomously with the help of the drive system and then unfold its sun sails. Only then is the rover ready to drive and survive.” The rover chassis developed and designed at DLR, including the carbon structure, and the entire righting and locomotion system have just been completed and delivered to France for further assembly.

By the summer of 2023, all of the rover’s instruments and subsystems will be installed at the CNES in Toulouse, where it will also receive its solar panels, the energy system, the radio system for contact with the earth, and the on-board computer. Then extensive tests of the rover are pending. It is being tested to see how well it withstands the vibrations of the rocket launch and the extreme temperature fluctuations of more than 200 degrees Celsius on Phobos. In 2024, the small rover will then start from Japan to the Mars moon.

Source: German Aerospace Center (DLR)

This article was written by Nadja Podbregar

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The original to this post “tricky mission to solve the mystery of the moons of Mars” comes from scinexx.