We know more about our planetary neighbor Mars than ever before, thanks to rovers like Perseverance, Curiosity and Vulcan, which are exploring there and learning about Earth’s geology and history. But the part of Mars that remains mysterious is its moons – Phobos and Deimos. These moons are small, measuring only 27 kilometers and 15 kilometers in diameter, respectively. The shape of the two satellites is also very strange, not spherical.
Scientists are interested in these moons because they want to understand their origins, but they could also hold clues to Mars’ history — because, for example, Phobos could preserve information about Mars’ ancient atmosphere information.
To learn more about Phobos, the Japanese space agency JAXA is planning a mission called “Mars Lunar Exploration” that will send a rover to this Martian moon and the German Aerospace Center (or DLR) will provide the instruments and structure for the rover. DLR is currently building various parts of the rover, including its propulsion unit and two instruments, to enable the rover to explore the lunar surface for a mission lasting approximately 100 days.
Designing a rover for Phobos
One challenge of building rovers to explore small moons like Phobos is the very low gravity there. Low gravity is helpful in some ways—for example, when landing on Mars, rovers need to slow down considerably from the very high speeds they’re traveling to a safe speed to land on the surface. This is made more difficult due to Mars’ thin atmosphere, but easier due to the planet’s lower gravity than Earth’s. Likewise, flying a helicopter on Mars can only be done in a thin atmosphere because of the low gravity.
But Phobos has such low gravity that flying too fast could send you spinning from the moon and into space. A rover suitable for this environment needs to be able to grip the ground in order to move across it.
“With the MMX rover, we are breaking new ground in terms of technology, because there has never been an exploration vehicle on wheels before on a small celestial body with one-thousandth the gravitational pull of Earth.” ,” explains Markus Grebenstein from the Institute for Robotics and Mechatronics at the DLR, who was part of the team studying the structure of the rover.
Landing is also difficult because the team cannot predict how the rover will land. “When the rover free-falls onto Phobos after separating from the spacecraft, it performs several “somersaults” on landing without taking damage, and then stops in an unpredictable position,” Grebenstein said. In this case, it must stand upright and deploy its solar panels autonomously with the help of a propulsion system. “
Exploring the moons of the red planet
To investigate the Martian moon, the MMX rover will be equipped with instruments including radiometers and spectrometers to understand the lunar surface. The rover will be able to collect data on factors such as surface temperature and porosity, which will allow researchers to combine these The data were compared with similar data on asteroids.
The overall goal is to understand how Phobos formed, such as whether it was an asteroid lingering near Mars and being gravitationally attracted , or whether it was a piece of Mars that was blown away by a large impact millions of years ago.
The camera on the rover will be used for navigation, but should also be able to film the first Close up image of the Moon’s surface.
The hardware needs to be very sturdy to run on MMX, as Phobos is not only cold and has no atmosphere, but the low gravity makes it difficult to move around. DLR System Stefan Barthelmes of the Institute for Dynamics and Control said the rover “will travel very carefully at a few millimeters per second in order to maintain contact with the ground via its special wheels in low gravity”. )
The goal is to launch the MMX rover in 2024, enter Mars orbit in 2025, and land on Phobos in 2027.
