Phobos and Deimos, named after the Gods of Fear and Terror and sons of the Greek God Mars, are the two only natural satellites of the Red Planet. Though many probes have visited and studied Mars, there has not yet been any actual missions to these two bodies whose origins we do not know. The two leading hypotheses are that they were gravitationally captured by Mars or that they originate from an impact between the planet and another massive object, similar to how the Moon was formed.
The best way for us to determine their origins is to send a probe, collect a sample and bring it back to Earth for studying. This is the exact objective of the Martian Moons eXploration mission or MMX. Built by Japan’s space agency JAXA and in collaboration with France’s CNES and Germany’s DLR, this international mission is planned to launch from Japan in 2026. The probe consists of three sections, a propulsion and navigation module to reach Mars, a landing module to safely touchdown on the surface of Phobos and a return capsule that will bring back these samples to Earth in July 3031.
MMX Modules (JAXA)
Mission Layout
One year after launch, MMX should insert itself in an orbit around Mars that allows it to study both Phobos and Deimos from afar. It is then planned to orbit Phobos, the largest of the two moons, and survey its surface for about 3 years. During this time, it will analyse the moon’s surface and determine a safe landing zone. Simply orbiting Phobos will also allow teams of scientists to better understand its density and mass distribution. Given the asteroid’s small size and low mass, its surface gravity is a mere 0.01% of Earth’s which makes interactions with its surface very complex and hard to predict.
IDEFIX Rover on Phobos (DLR)
Before attempting a landing, the probe will descend within 100m of the surface and drop a small rover named IDEFIX produced by the CNES and DLR. This rover will serve as a technology demonstrator to prove it is possible to drive in a “milligravity” environment. This kind of development can be very helpful for future missions that might plan to mine asteroids. Beyond this technological feat, IDEFIX will closely observe the interaction between its wheels and the surface of Phobos. This will allow us to further understand milligravity interactions that have never been tested before which is crucial for a safe landing of the MMX mothership. In order to study the surface, IDEFIX will also carry scientific instruments such as spectrometers to identify minerals and determine a surface temperature. Scientists plan to compare the observed minerals to ones found on the surface of Mars by other probes and rovers. Matching results would be a very good indicator that Phobos was ejected from Mars during a potential impact for example. Beyond this, IDEFIX can also study the history of Mars by observing ejecta that arrived upon Phobos throughout its lifetime. After it has completed its 100 day mission IDEFIX will be left on the surface to be potentially used as a communications relay for future Martian missions.
MMX Landed on Phobos (JAXA)
Once MMX has accomplished all of its objectives in orbit, it will attempt a landing. This is done at the end of the mission as the probe may crash upon landing. That is why the probe does all the science it can from orbit, transmits its findings and once it has nothing left to do in orbit it attempts a landing. Upon the surface, MMX will gather about 10g worth of regolith and subsurface material and conduct additional scientific experiments. After this 2.5 hour operation, the return module will leave the Martian system and return to Earth to safely land in Australia by 2031. If all goes well, this will be the first ever sample return from Mars.
Impact of the Mission
Beyond the science of this mission, MMX will also share the highest resolution images of Mars and its moons ever with its 4k and 8k cameras. These will bring us closer to Mars than we have ever been and are set to deliver magnificient pictures for all to admire. With more technological demonstrators that cannot be described in a few words here, the mere proof of concept that a sample return from Phobos represents is certain to accelerate the development of future robotic and manned missions to Mars in the decade to come. Fear and Terror might hold the key to understanding the early Solar System and provide us with more information on planet formation.
Bibliography
JAXA MMX mission overview:
- https://www.mmx.jaxa.jp/en/mission/
ESA MMX factsheet:
- https://www.esa.int/Science_Exploration/Space_Science/MMX_factsheet
DLR on IDEFIX:
- https://www.dlr.de/en/latest/news/2023/02/rover-on-the-home-stretch-to-the-martian-moon-phobos
- https://www.dlr.de/en/latest/news/2022/04/a-rover-for-mars-moon-phobos
Video overview of mission:
- https://www.youtube.com/watch?v=-a0e8AKOWg0
