v0.2 - 25-04-2020

Phobos and Deimos

As of yet, no missions have successfully landed on the Martian moon Phobos or Deimos. These moons are so small that their gravity is almost non-existent and only 0.06 and 0.03 per cent of the earth's gravity. The Russian Phobos-Grunt mission would gather samples from Phobos but failed to leave earth. The next mission set to land on Phobos is the Japanese Martian Moon Exploration mission launching in 2024.

The Phobos 1 and 2 missions were part of the Soviet Phobos program of 1988. Both vehicles weighed about 6.2 tons which made them the heaviest interplanetary missions at that moment. The mass of the vehicle meant it was launched on top of the Proton rocket.

Phobos 1, launched in July 1988 failed several weeks into its Martian transit. The issue was traced back to a wrong control input causing the attitude thrusters. A single hyphen led to the loss of the mission. Phobos 2 was launched fice days later failed while in orbit of Mars.37 images were send back of the Martian surface and atmosphere. During this time three preliminary encounters with Phobos were done. The mission failed just before the planned intersection with Phobs during which it would deploy two landers.  

The mission was first designed to perform a soft landing on the moon, however, due to the low gravity, the lander would simply bounce off. Initially, a harpoon-like system was included that would fire 20-30 meters above the surface. This proved to be quite an engineering challenge. in addition, to the spacecraft itself, a small hopper would be deployed onto the surface. This hopper was called Frog and weighed about 50 kg. Using spring-loaded legs Frog could manoeuvre from location to location performing surface studies.  

The Martian Moons eXploraion mission or MMX is a JAXA led sample return mission to Phobos. The mission is set to launch in 2024 and reach Phobos in  2025 with a return date now in august 2028. After landing on the moon two sampling methods will be used to maximise the change of mission success. The first is a Coring Sampler to gather samples up to 2cm on the surface, while the other is a pneumatic sampler to gather surface samples. Both systems only have about 2.5 hours to gather 10 grams of soil. After the samples have been gathered the probe will fly past Deimos and return to earth.

Besides the sampler onboard MMX, a small Phobos rover is being designed by DLR and CNESS that will be deployed on the surface. 

Phootprint is a proposed Phobos sample return lead by ESA. Not much is known about the lander except that it will launch on Ariane 5 in 2024 or 2026. The satellite will anchor itself onto the Phobos surface to ensure it does not fall off. After landing it will gather about 800g of regolith and return about 100 grams. Similar to the NASA-ESA Mars sample return it would use a passive earth return concept. That means the ballistic coefficient is such that it does not need a parachute for a safe landing.