A Japanese space mission is about to launch towards Mars. But it will not land on the planet itself. Instead, the Martian Moons Exploration (MMX) mission will focus on Phobos, the bigger of Mars’s two small moons.
The mission will lift off on Monday October 19 at 20:41 BST on an H3 rocket from the Tanegashima Space Center, in the south of Japan.
This will start a five-year mission, during which the spacecraft will orbit and explore Phobos, deploy a lander, touch down and collect soil and small pebbles. In a world first, these samples will be delivered to Earth for study in laboratories.
MMX is led by the Japanese Aerospace Exploration Agency (Jaxa), in collaboration with the US, France, Germany and the European Space Agency (Esa). The overall science objective is to unravel the origins of the two Martian moons, the smaller of which is called Deimos. Mission scientists also want to examine the wider evolution of Mars and its local environment in space.
We still have no clear understanding of how the red planet got its moons. These natural satellites could have been hapless asteroids that were passing by Mars when they got captured by its gravity.
Another possibility is that that they formed when an asteroid collided with Mars, causing rocky material to be thrown out into space. Gradually, this material coalesced into Phobos and Deimos. The MMX mission will give us Phobos’s chemical composition, which could help distinguish between theories.
Grabbing samples from Phobos will be no easy task, however. Russia tried this in 2011 with its Phobos Grunt mission. The spacecraft launched successfully to low Earth orbit, but failed to fire its engines to send it toward Mars.
However, Jaxa is well placed to succeed. The space agency has already proved that it can return samples from asteroids with its Hayabusa space missions, which lasted from 2003-10 (Hayabusa) and 2018-20 (Hayabusa 2).
MMX will trial sophisticated sampling techniques designed for Phobos’s low gravity. The moon has about 0.1% the gravitational pull that Earth does. This means that a human on Phobos could jump a distance of 1.5 km horizontally without much effort.
The mission will also be a test of communication between the spacecraft and a newly developed ground station. After launch and deployment, MMX will take a year to reach Mars, arriving in August 2027. It will first circle the red planet before slipping into orbit around Phobos about a month later.
The spacecraft consists of three modules with distinct functions: a propulsion module to get MMX into orbit around Mars, an exploration module with landing and sample collection gear and a return module to deliver the sample to Earth.
The mission will make use of 13 science instruments to explore Phobos. High resolution cameras called Tengoo and Orochi will map the surface and a laser altimeter (Lidar) will build up a picture of the moon’s contours. Lidar uses laser pulses to measure the distance from the spacecraft to features on the surface.
An infrared spectrograph called MIRS will survey Phobos’s minerals, while a gamma ray and neutron detector, called Megane, will determine the moon’s elemental composition. From a greater distance, MMX will also gather data on Mars’s smaller moon Deimos.
Read more: How did Mars get its moons? Japan’s MMX space mission aims to solve the puzzle
The instruments will send back data that controllers will use to decide where and how to land the spacecraft on Phobos.
In early 2029, the MMX exploration module will deploy a small microwave oven-sized rover called Idefix, which has been developed jointly by Jaxa, the French space agency Cnes and the German Aerospace Center (DLR). Idefix will drop down onto Phobos’ surface from between 40 and 100m in altitude.
The rover will then right itself and travel over the surface during an operational period expected to last about 100 days. It will be using several sensors, including a Raman spectrometer and radiometer, to make a final call about where the exploration module should land.
In 2030, the module will swoop down and land on Phobos, remaining on its surface for about 2.5 hours. It will be able to extract samples from the surface once or possibly twice by landing again at a different location. The ability to sample from more than one place on Phobos is vital to understanding the moon’s composition.
The exploration module will use either an instrument called the C-sampler to drill a core or a device knowns as the P-sampler, which blows a jet of nitrogen gas to blast soil and loose pebbles off the surface and into a sample collection chamber.
The C-sampler would be able to collect a core from up to 2cm below the surface. This would provide the mission with a sample composition unaltered by solar radiation, which causes chemical changes to planetary surfaces over time. The P-sampler is a back-up option, but carries some small risk of toppling the spacecraft in low gravitational fields like the one on Phobos.
Having gathered at least 10 grams of material, the spacecraft will leave the Martian moon, separating from its landing gear. It will then travel back to Earth, arriving in 2031. On its approach, the spacecraft will eject its sample probe, which will then descend through Earth’s atmosphere. It will land using parachutes in Australia, where it will be recovered and transported to Japan.
A potential side-benefit of the mission is that samples from Phobos might also include material from Mars. Phobos closely orbits the red planet and is thought to be constantly hoovering up Martian soil. This soil is thought to be regularly ejected from the planet’s surface by asteroid impacts.
MMX could therefore be considered a lite-version of the Mars Sample Return (MSR) mission. MSR, a collaboration between the US and European space agencies, would have sent rock samples from the Martian surface to Earth. However, budgetary pressures led to the programme being effectively cancelled by US Congress.
If scientists get lucky with the samples from MMX, they might get a nice consolation prize.
Daniel Brown does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.