SCIENCE

Unraveling the origin and evolution of the Solar System and Mars

Although Mars today is a cold desert and cloaked in a thin atmosphere, the ancient planet is believed to have possessed an environment more similar to Earth, with a thick atmosphere and abundant water, including oceans and lakes, and an active water cycle. As a small moon of Mars that has not undergone the same geologic evolution of the planets, Phobos preserves evidence of the early evolution of the Mars system, allowing us to investigate the planet's environmental evolution and the processes involved in the formation of a habitable planet.

Getting to know Phobos

What is the potato-like Martian moon?

In 1877, US astronomer Asaph Hall discovered two small moons orbiting Mars: Phobos and Deimos. Both are small celestial bodies, with the larger Phobos only about 1/160th the size of Earth's moon, with an irregular, potato-like shape and surface covered with different sized craters. The moons have low densities and dark surfaces, with the properties of the reflected light similar to that of carbonaceous asteroids. A comparison of the characteristics of the Earth's moon and Mars's moon, Phobos, is shown below.

Item	Phobos (Martian moon)	The Moon (Earth's moon)
Distance from Earth	230 ~ 400 million km	384,000 km
Diameter	Up to 27 km	3,474 km
Surface Gravity	1/1700 of Earth	1/6 of Earth
Age	???	4.5 billion years
Origin	"Giant impact hypothesis" vs "Capture hypothesis"	"Giant impact hypothesis" is the lead theory
Distance from the planet's surface	6,000 km	384,000 km
Planet-facing side	The same side always faces Mars	The same side always faces Earth
Day-night cycle	12 hour day and 12 hour night	14-day daytime and 14-day night
Future	Slowly approaching Mars and may break apart in the future.	Slowly drifting away from Earth

Mars — Image credit: NASA
Earth — Image credit: NASA Goddard Space Flight Center / Reto Stöckli
Moon — Image credit: NASA/Goddard/Lunar Reconnaissance Orbiter
PHOBOS — Image credit: NASA/JPL-Caltech/University of Arizona

The evolution of space exploration

From observing to retrieving samples

Humankind has explored the history of the Solar System by observing distant celestial bodies through telescopes and spacecraft, and by examining meteorites—actual physical samples—that have fallen to Earth. Then the Apollo Program marked a milestone when humans travelled to another celestial body, our Moon, and brought home rock and grain samples to Earth. This technology was carried forward into the Hayabusa and Hayabusa2 mission, which successfully collected samples directly from asteroids.

The next destination is the Martian sphere. The MMX mission aims to travel to Phobos, collect rock and grain samples, and return this material to Earth. We are now advancing into an era where we not only observe distant celestial bodies, but also obtain and analyse their physical material firsthand.

Illustration of the MMX spacecraft landed on Phobos with Mars in the background

The stage for science

Three reasons for the selection of Phobos as the exploration site

01
The next challenge, building on our past experience
Mars has strong gravity, presenting significant technical challenges to returning samples to Earth from the planet surface. On the other hand, Phobos is a relatively small celestial body, allowing leverage of the small body exploration and sample collection technology honed during the Hayabusa and Hayabusa2 missions. Compared to Deimos, more observational data has been gathered for Phobos, including imagery, topography, and temperature readings, which is an advantage when selecting a suitable landing site.
02
The characteristics of both Mars and small bodies, offering a wealth of information
The surface of Phobos is extremely dark, but nevertheless features distinct regions with "red" and "blue" spectral characteristics. (Referring to whether the reflected light is greater at longer, redder wavelengths, or bluer, shorter wavelengths.) This suggests that Phobos may contain a greater diversity of material than Deimos. Investigating the moon's origins will provide insight not only into the Martian moons themselves, but also into the formation and evolution of small celestial bodies.
03
An insight into the history of the Mars sphere
Located approximately 7,000 km from Mars, Phobos is believed to have accumulated a significant amount of material ejected from the Martian surface. It is estimated that Phobos will have over 100 times the amount of Mars material compared to the outer moon, Deimos. By analysing the samples for material with Martian origin, the Phobos sample will probe the history of the formation and evolution of the Martian sphere.

Scientific objective

Deciphering the origin and evolution of the Solar System and Mars through Phobos

MMX will investigate the nature of the Martian moon Phobos from multiple perspectives through remote sensing and in-situ observations, and the sample returned to Earth. The mission aims to confirm the origin of Phobos, gain insight into material transport and the planetary formation processes in the Martian region which connects the inner and outer Solar System, and explore how the Mars sphere formed and evolved.

Mystery01Settling the debate: giant impact vs. capture

The origin of the Martian moons remains one of the great debates regarding the origin of the Solar System. There are two competing theories: the "giant impact" hypothesis suggests that the moons formed after a massive collision with Mars, while the "capture" hypothesis postulates that the pair originated as asteroids elsewhere in the Solar System and were subsequently captured by Mars's gravity. MMX aims to determine the origin of Phobos through detailed observation and the analysis of over 10g of returned samples. Furthermore, by investigating where the Phobos material originated in the Solar System, and identifying when it migrated into the Martian sphere, the mission seeks evidence for how the Solar System formed, and the transport of material within it. Observations of Deimos will also provide insight into the second moon's origins, highlighting any differences between the inner and outer moon.

Diagram of the giant impact hypothesis — The hypothesis that a large body collided with Mars and the debris coalesced to form the moons

Diagram of the capture hypothesis — The hypothesis that asteroids from the outer Solar System were captured by Mars's gravity

Mystery02What can Phobos reveal about the evolutionary history of the Mars system?

Orbiting close to Mars, Phobos is believed to be covered with a layer of material ejected from the Martian surface during meteorite impacts. This material of Martian origin may hold a record of how the planet's surface environment has changed throughout Mars's long history. Clues such as evidence of water, indicating ancient oceans and lakes from approximately 4 billion years ago, as well as the chemical properties, origins of organic matter, and even potential evidence of past life (biosignatures) could be locked in these grains. Additionally, by investigating the evolution of the Phobos surface and circulation of material within the Martian atmosphere, MMX aims to understand the mechanisms that drove the evolution of the Martian sphere.

Diagram of material ejected from the Martian surface accumulating on Phobos

13 mission instruments

To unravel the mysteries of the Martian moons, we must decide what to observe with which instrument, and which samples to collect. The MMX spacecraft will use thirteen scientific mission instruments to explore the moons, and the landing site will be selected based on remote-sensing data. The goal is to return more than 10g of material to Earth.

Remote sensing and in-situ observation instruments

During the first half of the mission, MMX will construct the global shape and topography model of Phobos, conduct high-resolution observations, and select the landing site. During the second half, the focus will be on detailed observations of specific locations on Phobos and also conducting observations of Mars, particularly the atmospheric dynamics, and observations of the second moon, Deimos.

01・02

TENGOO

Telescopic high-resolution camera for observing the global surface and topography of Phobos.

TENGOO stands for “TElescopic Nadir imager for GeOmOrphology”.
This is a telescopic (narrow angle) camera for observing the detailed terrain on the surface of the Martian moons. TENGOO can capture surface images at a resolution of about 40cm and obtain information on the distribution of different materials that correspond to the collected samples. It can also be used for checking safety at the planned landing site.

OROCHI

Wide-angle multi-wavelength camera to capture the distribution of material across the Phobos surface in visible light.

OROCHI stands for “Optical RadiOmeter composed of CHromatic Imagers”.
This is a wide angle camera to observe the topography and material compositions on the Martian moon surface. It can take images in the visible light reflected from the Martian moon's surface at multiple wavelengths to identify hydrated materials and organic matter, both globally and at the sampling locations.

Kameda Shingo

Rikkyo University, Professor

Speciality: Planetary physics
I have previously been involved in the development of the cameras onboard the asteroid explorer Hayabusa2, and the Mercury spacecraft, Mio. I hope to make use of the experience gained with these Solar System explorers to ensure the MMX cameras reach their best and highest performance.

LIDAR

Laser range finder that can measure the distance between the spacecraft and moon surface.

LIDAR stands for “Light Detection And Ranging”.
This is a ranging instrument to observe information on the shape of the Martian moon surface. LIDAR uses a laser to reflect light from the moon's surface. The surface altitude and albedo distribution can be derived from measuring the time taken for reflected light to return, and the energy of the reflected light.

Senshu Hiroki

Chiba Institute of Technology, Senior Fellow

The laser altimeter continuously measures the altitude of the spacecraft, which is changing continuously. The data obtained is a series of numbers, which is not as spectacular as a camera image, but it is interesting because it is acquired over a long period of time with high accuracy. Every day, I think hard about how to make this data exciting for as many people as possible.

MIRS

Near-infrared spectrometer for investigating the mineral composition of the Phobos surface.

MIRS stands for “MMX InfraRed Spectrometer”.
This is a near-infrared observation instrument to clarify the characteristics of minerals constituting the Martian moon. With spectroscopic measurements in near-infrared light in the 0.9 - 3.6 microns spectral band, MIRS can measure the distribution of hydrous minerals, water related substances and any organic matter over the whole surface and be used for the selection of sampling locations. MIRS is being developed at LESIA-Paris Observatory in collaboration with four other French laboratories (LAB, LATMOS, LAM, IRAP-OMP) and in partnership with the French space agency, Centre National d'Etudes Spatiales (CNES).

Maria Antonietta Barucci

Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Professor

Speciality: Exploration of small bodies
After my deep involvement in Cassini-Huygens, Rosetta, BepiColombo, OSIRIS-REx and Hayabusa2, I am particularly proud to participate in MMX, contributing with the imaging spectrometer MIRS for this exciting mission. MIRS will detect mineral and organic compounds present on Phobos and Deimos, contributing to understanding their nature and origin. MIRS will also investigate the processes of the evolution of the Mars environment. My challenge is to make known what it is unknown.

MEGANE

Gamma-ray and neutron spectrometer to investigate the elemental composition of the Phobos surface.

MEGANE stands for "Mars-moon Exploration with GAmma rays and NEutrons".
MEGANE is a gamma-ray and neutron spectrometer that will measure which chemical elements that comprise Phobos. The gamma-rays and neutrons detected by MEGANE are generated by cosmic rays that continually bombard Phobos's surface, and from natural radioactivity in the moon's surface rocks. MEGANE's compositional measurements will provide key information to help determine the origin of Phobos, study surface processes on Phobos, and support site selection for the collection of samples by the MMX spacecraft, providing critical context for those samples. MEGANE is being developed in partnership with the US space agency, NASA.

David J. Lawrence

The Johns Hopkins University Applied Physics Laboratory, Planetary Scientist

Speciality: Physics; planetary and space science
The MEGANE team is very pleased to participate in the MMX mission, and bring our experience in planetary gamma-ray and neutron spectroscopy to help us all understand fascinating questions about Mars’s moon Phobos. We look forward to our continued work with our engineering and scientific colleagues on this exciting mission.

CMDM

Dust monitor for detecting dust rings around Mars.

CMDM stands for “Circum-Martian Dust Monitor”.
This is a device for clarifying the dust environment around the Martin moon. By measuring the dust abundance of 10 μm or more in size, the frequency of collision of celestial bodies that generate dust and the phenomenon of dust reintegration on Martian moons can be investigated.

Kobayashi Masanori

Planetary Exploration Research Center Chiba Institute of Technology Senior Staff Scientist

Speciality: Planetary exploration
I am extremely excited to be able to participate in the MMX mission. We are aiming to discover the Martian circulation dust that has been theoretically predicted for many years but has not been found yet. Although there is a long way to go before we get to the goal, we try our best.

MSA

Mass spectrometer for measuring the ion environment around Mars and the moons.

MSA stand for “Mass Spectrum Analyzer”.
This is an instrument to clarify the ion environment around the Martian moon. The presence of ice inside the Martian moon, the weathering effect on the Martian moon surface, and the amount of Martian atmosphere dissipation can be investigated by measuring ions released from the Martian moon, ions released from Mars, and the ions in the solar wind.

Yokota Shoichiro

Osaka University, Associate Professor

Speciality: Planetary Science
We are fortunate to be part of the MMX project as the MSA team. In addition to our previous observations around Earth and Mercury, we hope to achieve observations of charged particles and magnetic fields around Mars and Phobos.

IDEFIX

A mobile rover to explore the surface of Phobos ahead of the main spacecraft.

The MMX rover will land on Phobos before the main spacecraft, and explore the surface of the Martian moon. These explorations will reveal a variety of physical properties about the surface regolith, which will reduce risk during spacecraft landing and sampling operations, as well as acquire valuable calibration data for scientific observations. The MMX rover is being jointly developed by the Centre National d'Etudes Spatiales (CNES) and the German Aerospace Center (DLR).

Julien Baroukh

Rover Project Manager, CNES

The CNES and DLR teams have poured their passion and expertise into developing IDEFIX (the rover) for the MMX mission. We are very much looking forward to seeing the rover explore the surface of Phobos and help unravel the mysteries surrounding the origin and history of the Martian moons. We are deeply grateful to JAXA for giving us the opportunity to take part in this wonderful journey.

Sample collection and retrieval

The MMX spacecraft will perform two soft landings on Phobos, spending approximately 2~3 hours on the surface to collect at least 10g of material. Reliably collecting the required sample in a microgravity environment and on an unfamiliar surface presents a significant mission challenge.

CSMP

A corer sampling mechanism that collects material by excavating the surface of Phobos to a depth of approximately 2cm.

The C (corer) Sampler aims to collect subsurface material from the Martian moon down to a depth of 2cm. The sampler consists of a robotic arm and cylindrical corer designed to drive through the surface regolith on Phobos and safely store a core soil tube in the sample return capsule.

Kato Hiroki

Chief Researcher, Research and Development Directorate, JAXA

As a robotics specialist, I am looking forward to a future where more robotics missions are launched into space. And, the MMX Sampler is one step in history that we can be proud to share with the world. If MMX succeeds in sample return, there will be more and more talk of human Mars exploration, in other words, we will feel that we are contributing to the progress of humanity. MMX will be the first in the World to successfully return samples from Phobos.

P-SMP

A pneumatic sampling mechanism for collecting surface material by injecting nitrogen gas.

The P (pneumatic) sampler uses pressurised gas to loft material from the surface of the Martian moon into the sample container in a fraction of a second. The P-Sampler is being contributed to the MMX spacecraft by NASA and has been fabricated by Honeybee Robotics in Altadena, California.

Kris Zacny

Vice President of Exploration Systems Division at Honeybee Robotics

Speciality: Space mining and drilling, sample acquisition and handling, In-Situ Resource Utilization (ISRU)
We are absolutely thrilled to be part of the MMX mission and help with bringing Phobos and Martian samples back, for a first time in human history. Our pneumatic mining technology has been in development for over two decades and we are very fortunate that NASA and JAXA has selected it for this mission. Go MMX!

SRC

Capsule for delivering the Phobos sample to Earth.

The Sample Return Capsule (SRC) will store the samples collected from the Martian moon by the C-Sampler and P-Sampler and pass through the Earth's atmosphere to bring the samples back to the Earth's surface.

Suzuki Toshiyuki

Research, Test and Operation Technology Group Manager, JAXA Institute of Space and Astronautical Science (ISAS)

Speciality: thermal protection system, aerodynamics
I am very proud to be able to participate in the MMX mission. I will do my best to ensure that the valuable samples from the Martian moon surface can be brought back to Earth safely and reliably.

Development of exploration technology

With eyes on the future of lunar and planetary exploration, MMX aims to develop new exploration technology. Leveraging the MMX flight opportunity, the mission will carry two technology demonstration instruments to test capabilities in the actual space environment.

IREM

Radiation environment monitor for measuring high-energy particles in interplanetary space.

The Interplanetary Radiation Environment Monitor (IREM) will measure the space radiation environment and acquire the energy spectrum of high-energy protons (solar energetic particles: SEPs) generated from events such as solar flares. Measuring the background radition environment around Mars is important for the safety of future crewed missions, and to establish methods for exposure dose evaluation.

Aida Mari

Researcher, Space Environment Group, Research Unit I, Research and Development Directorate, JAXA

Speciality: Space radiation and electrical engineering
There have been very few observations of the radiation environment near Mars.
IREM will make observations almost continuously throughout the MMX operation period.
I will do my best to acquire as much valuable radiation data as possible and contribute to a better understanding of the space environment!

SHV

Ultra-high definition cameras for capturing images of the Martian moons at 4K and 8K resolution.

Two Super Hi-Vision (SHV) cameras are being developed in collaboration with NHK (Japan Broadcasting Corporation) to capture Mars and the Martian moons at 8K and 4K resolution. These photographs will become the highest definition images ever captured of the system, allowing this exciting mission to be brought to life for a wide audience.

Funatsu Ryohei

Japan Broadcasting Corporation (NHK), Engineering Administration Department, Expert

Speciality: Broadcast cameras
We are very pleased to be participating in the MMX mission and to equip the spacecraft with NHK’s 8K/4K cameras. We will work on the camera development so that we can deliver to everyone ultra-high definition images of the Martian sphere that no one has seen before.

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