Search

The present paper addresses the development of a closing and sealing system for a container which shall safely bring 100 g of regolith from the surface of Phobos, one of the moons of Mars. Based on a set of requirements defined by the ESA (European Space Agency), a design of the closing and sealing system was made and FEA (Finite Element Analysis) was employed to validate the design. The closing and sealing mechanism along with the Vault (container to be sealed) proved the capability to overcome the Robotic Arm misalignments, to ensure the Vault closing and to maintain the leak tightness (maximum admissible leak rate of 10−4 mbar*l/s Helium) during the trip back to Earth. All these features were validated following an extensive test campaign implying mechanical loads, shocks, thermal vacuum cycling, dust contamination, impact tests and several functional verifications. The mechanism demonstrated the targeted maturity level (TRL 5) and it can be further developed in order to be qualified for a specific mission/application.

Martian moons exploration, MMX, is the new sample return mission planned by the Japan Aerospace Exploration Agency (JAXA) targeting the two Martian moons with the scheduled launch in 2024 and return to the Earth in 2029. The major scientific objectives of this mission are to determine the origin of Phobos and Deimos, to elucidate the early Solar System evolution in terms of volatile delivery across the snow line to the terrestrial planets having habitable surface environments, and to explore the evolutionary processes of both moons and Mars surface environment. To achieve these objectives, during a stay in circum-Martian space over about 3 years MMX will collect samples from Phobos along with close-up observations of this inner moon and carry out multiple flybys of Deimos to make comparative observations of this outer moon. Simultaneously, successive observations of the Martian atmosphere will also be made by utilizing the advantage of quasi-equatorial spacecraft orbits along the moons’ orbits. Graphical Abstract

The Martian Moons eXploration (MMX) spacecraft is equipped with two cameras, i.e., the TElescopic Nadir imager for GeOmOrphology (TENGOO) and the Optical Radiometer composed Of CHromatic Imagers (OROCHI), for the scientific observation of the Martian moon Phobos. OROCHI is a wide-angle multiband camera system comprising seven cameras with different bandpass filters and one monochromatic camera in the visible and near-infrared range. Thus, OROCHI can simultaneously obtain multiband images. Previous space observations have revealed that the reflection spectra of Phobos exhibit regional differences, including a red unit and a blue unit with weak redness. Moreover, Phobos shows an absorption band near 650 nm, attributed to the red unit of Phobos. Global observations using OROCHI require the determination of such regional variations with high precision; therefore, we must reduce noise in the optical system design. In this study, to meet this requirement, we focus on stray light reduction. Stray light is a source of noise generated by reflections at surfaces of optical components (e.g., sensors, filters, lenses, and lens barrels). We design simulation models of the OROCHI optical system, measure the reflectance of its charge-coupled device (CCD) image sensor, and conduct stray light analysis via ray tracing. We estimate the ratio of the stray light intensity to the target signal intensity by deriving both the reflected (constituting stray light) and unreflected rays. We show that placing the filter away from the sensor and reducing the reflectances of the filter and lenses effectively reduce stray light. Such approaches are incorporated into the preliminary design of OROCHI.

The science operations of the spacecraft and remote sensing instruments for the Martian Moon eXploration (MMX) mission are discussed by the mission operation working team. In this paper, we describe the Phobos observations during the first 1.5 years of the spacecraft’s stay around Mars, and the Deimos observations before leaving the Martian system. In the Phobos observation, the spacecraft will be placed in low-altitude quasi-satellite orbits on the equatorial plane of Phobos and will make high-resolution topographic and spectroscopic observations of the Phobos surface from five different altitudes orbits. The spacecraft will also attempt to observe polar regions of Phobos from a three-dimensional quasi-satellite orbit moving out of the equatorial plane of Phobos. From these observations, we will constrain the origin of Phobos and Deimos and select places for landing site candidates for sample collection. For the Deimos observations, the spacecraft will be injected into two resonant orbits and will perform many flybys to observe the surface of Deimos over as large an area as possible. Graphical Abstract

An altimeter is a critical instrument in planetary missions, for both safe operations and science activities. We present required specifications and link budget calculations for light detection and ranging (LIDAR) onboard the Martian Moons Exploration (MMX) spacecraft. During the mission phase, this LIDAR will continuously measure the distance between the spacecraft and its target. The time-series distance provides important diagnostic information for safe spacecraft operations and important information for geomorphological studies. Because MMX is a sample return mission, its LIDAR must accommodate physical disturbances on the Martian satellite surface. This resulted in changes to the optical system design. Graphical abstract

The Martian Moons eXploration mission, currently under development by the Japan Aerospace Exploration Agency (JAXA), will be launched in 2024 with the goal of retrieving pristine samples from the s...

The Martian moon Phobos is the target of the upcoming JAXA Martian Moons eXploration (MMX) mission. There are currently no known samples of Phobos, so spacecraft hardware testing and scientific studies require Phobos regolith simulants. Here, we present two new Phobos regolith simulants: Phobos Captured Asteroid-1 (PCA-1) and Phobos Giant Impact (PGI-1). These two simulants reflect the two hypotheses for Phobos’s formation, and thus the two broad possibilities for composition. This work follows previous efforts to document the development of mineralogically accurate simulants, in an effort to overcome past pitfalls with inappropriate uses of simulants. We report physical and geotechnical properties of PCA-1 and PGI-1, including their reflectance spectra, grain size distributions, abrasivity, cohesion, strength, and hardness. Our intent is for PCA-1 and PGI-1 to be open standards for Phobos simulants, and we present the simulant recipes and production methodology for use and modification by the community.

Quasi-satellite or distant retrograde orbits are stable orbits in the restricted three-body problem will be used in remote planetary satellite missions like JAXA’s Martian Moons eXploration (MMX). Due to Phobos’ irregular gravity field, the proximity operations of the MMX mission require sophisticated techniques for transfers and maintenance between different quasi-satellite orbits. This paper focuses on the design of transfer trajectories between Quasi-Satellite Orbits (QSO) around Phobos. We utilize horizontal bifurcated Multi-Revolution Periodic QSOs (MP-QSOs) that are found in the vicinity of an ellipsoidal Phobos under the assumptions of the circular Hill Problem. Transfer strategy via MP-QSOs is explored through transfer maps that illustrate transfer design space between different altitudes QSOs. It is found that transfers via MP-QSOs provide insights on minimum Δ V transfers and the parameters determining the transfer cost. The proposed transfer method is explicitly applied to MMX baseline QSOs. This research has identified that transfers between high(100 × 200 km)-to-mid(50 × 100 km), mid-to-low(30 × 50 km), and lower altitude( 30 km) QSOs via MP-QSOs can be achieved with as low as 11.63 m/s, 3.99 m/s, 1.74 m/s, and 0.97 m/s, respectively.

The time dispersion effect affects the accuracy of solar time difference of arrival (TDOA) navigation. In this celestial autonomous navigation, Mars's moons are reflecting celestial bodies, and their shape affects the TDOA dispersion model. In the modelling process of traditional methods, the moons of Mars (Phobos and Deimos) are regarded as points, which causes the model to be inaccurate. In order to solve these problems, we simplified the Mars's moons into ellipsoids or solid diamonds, and then established a TDOA model with the nonspherical Mars's moons as reflecting celestial bodies through differential geometry and geometric optics. Finally, we analysed the time dispersion caused by the Mars's moons in theory. Theoretical analysis and experiments show that the point model error is 5·66 km, and the 3D model error is within 70 m. Thus, the 3D TDOA model established in this paper is meaningful. In addition, the Sun–Mars-moons–spacecraft angle, solar flare, three-axis length, and attitude of the Mars's moons have a great effect on the dispersion profile, while the Mars's moons-to-spacecraft distance has a small effect.

The Mass Spectrum Analyzer (MSA) will perform in-situ observations of ions and magnetic fields around Phobos as part of the Martian Moons eXploration (MMX) mission to investigate the origin of the Martian moons and physical processes in the Martian environment. MSA consists of an ion energy mass spectrometer and two magnetometers which will measure velocity distribution functions and mass/charge distributions of low-energy ions and magnetic field vectors, respectively. For the MMX scientific objectives, MSA will observe solar wind ions, those scattered at the Phobos surface, water-related ions generated in the predicted Martian gas torus, secondary ions sputtered from Phobos, and escaping ions from the Martian atmosphere, while monitoring the surrounding magnetic field. MSA will be developed from previous instruments for space plasma missions such as Kaguya, Arase, and BepiColombo/Mio to contribute to the MMX scientific objectives.

The JAXA’s Martian Moons Exploration (MMX) mission is planned to reveal the origin of Phobos and Deimos. It will remotely observe both moons and return a sample from Phobos. The nominal instruments include the TElescopic Nadir imager for GeOmOrphology (TENGOO) and Optical RadiOmeter composed of CHromatic Imagers (OROCHI). The scientific objective of TENGOO is to obtain the geomorphological features of Phobos and Deimos. The spatial resolution of TENGOO is 0.3 m at an altitude of 25 km in the quasi-satellite orbit. The scientific objective of OROCHI is to obtain material distribution using spectral mapping. OROCHI possesses seven wide-angle bandpass imagers without a filter wheel and one monochromatic imager dedicated to the observation during the landing phase. Using these two instruments, we plan to select landing sites and obtain information that supports the analysis of return samples. Graphical Abstract

Quantitative measurements and photographic imaging of the moons of Mars set limits on several key geological conclusions-such as the orbits of the moons. Other examples include their estimated bulk densities where Phobos has a density of ∼1.876 g/cm3 and Deimos has a lower and less certain density of ∼1.48 g/cm3. Imaging data reveals a low albedo of both moons – Phobos: ∼0.07; Deimos: ∼0.08. Also, Phobos manifests distinct redder and bluer units, whereas the surface of Deimos is globally comparable to the Phobos redder units with localized streaks of brighter material. Further, the libration of Phobos suggests interior density distributions potentially ranging from a generally homogeneous interior to a slightly heterogeneous composition, whereas Deimos lacks sufficient evidence to estimate its interior density distribution. Both moons are mantled in a global equivalent of dozens to hundreds of meters of regolith deposits, yet they differ in their surface characteristics. Other than scattered boulders and an underabundance of fresh craters, the surface of Deimos is generally smooth with most observable impact craters filled with regolith. Conversely, thousands of boulders are observed on Phobos, and the moon is heavily modified by larger craters that are crosscut by grooves and mantled with regolith deposits and smaller generally fresh and unfilled craters. Yet models that focus on many key questions are inadequately supported by definitive evidence, or lack definitive evidence altogether – and these questions must be considered open. For example, how were Deimos and Phobos produced? Where are their geological histories similar, and where do they diverge? Why are the global densities of Deimos and Phobos different from each other, and why are these densities less than typical rocky bodies? What are their present-day geochemical compositions, density distributions, and deeper interior structures? What are the natures of the Phobos red and blue surface units? When did the Stickney Crater ( $D \sim 9$ km) impact take place on Phobos and how did the Stickney impact alter the surface and interior of Phobos? How and when were the Phobos grooves produced? Do large impact craters on Mars emplace observable deposits of martian ejecta on the martian moons? Finally, how might we collect definitive evidence to address these open questions?

If humanity is ever to consider substantial, long-term colonization of Mars, the resources needed are going to be extensive. For a long-term human presence on Mars to be established, serious thought would need to be given to terraforming the planet. One major requirement for such terraforming is having the protection of a planetary magnetic field which Mars currently does not have. In this article we explore comprehensively for the first time, the practical and engineering challenges that affect the feasibility of creating an artificial magnetic field capable of encompassing Mars. This includes the concerns that define the design, where to locate the magnetic field generator and possible construction strategies. The rationale here is not to justify the need for a planetary magnetosphere but to put figures on the practicalities so as to be able to weigh the pros and cons of the different engineering approaches. The optimum solution proposed is completely novel, although inspired by natural situations and fusion plasma techniques. The solution with the lowest power, assembly and mass is to create an artificial charged particle ring (similar in form to a "radiation belt"), around the planet possibly formed by ejecting matter from one of the moons of Mars (in fashion similar to that that forms the Io-Jupiter plasma torus), but using electromagnetic and plasma waves to drive a net current in the ring(s) that results in an overall magnetic field. With a new era of space exploration underway, this is the time to start thinking about these new and bold future concepts and to begin filling strategic knowledge gaps. Furthermore, the principles explored here are also applicable to smaller scale objects like manned spacecraft, space stations or moon bases, which would benefit from the creation of protective mini-magnetospheres., Accepted for publication Acta Astronautica Sept 2021

MIRS (MMX InfraRed Spectrometer) is an imaging spectrometer onboard of MMX (Martian Moon eXploration) mission. MMX is a JAXA sample return mission that will be launched in September 2024 to Martian system, to bring back to Earth sample from Phobos, to observe in detail Phobos and Deimos and to monitor Mars’s atmosphere with observations of dust storm, clouds, and distributions of total amount of water vapor. The main objectives of the mission are to understand the origin of Martian moons, to constrain the processes for planetary formation and to understand the evolutionary processes of the Martian system. MIRS is a push-broom imaging spectrometer working in the range from 0.9 to 3.6 micron.

We have calculated the mass fluxes and dust particle fluxes the presence of which in orbits around Mars is due to collisions between meteoroids with Phobos and Deimos. The size distributions of dust particles captured in orbits around Mars are determined. Knowledge of the parameters of these particles is important when planning experiments to dust study in the system of Mars as part of future space missions.

著者人数: 16名, Accepted: 2019-11-03, 資料番号: SA1190189000

This work summarizes the review undertaken by a joint committee of the European Science Foundation and the National Academies of Sciences, Engineering and Medicine into the transfer of viable organisms from the surface of Mars to its moons-Phobos and Deimos-as a consequence of a giant impact on the martian surface. The possibility that viable organisms could survive ejection from Mars and subsequent deposition on Phobos and Deimos is an important consideration in determining whether samples returned from the moons by spacecraft missions be classified as restricted or unrestricted Earth return in the consensus planetary protection guidelines maintained by the Committee on Space Research (COSPAR) of the International Council for Science. Having reviewed recent research undertaken in Europe and Japan, the joint committee recommended that samples returned from the martian moons be classified as unrestricted Earth return. This paper is not intended to be a standalone work. Rather, it should be regarded as a summary of, and advertisement for, the material presented in the joint committee's formal report, Planetary Protection Classification of Samples Return Missions from the Martian Moons (the National Academies Press, 2019).

Potential microbial contamination of Martian moons, Phobos and Deimos, which can be brought about by transportation of Mars ejecta produced by meteoroid impacts on the Martian surface, has been comprehensively assessed in a statistical approach, based on the most probable history of recent major gigantic meteoroid collisions on the Martian surface. This article is the first part of our study to assess potential microbial density in Mars ejecta departing from the Martian atmosphere, as a source of the second part where statistical analysis of microbial contamination probability is conducted. Potential microbial density on the Martian surface as the source of microorganisms was estimated by analogy to the terrestrial areas having the similar arid and cold environments, from which a probabilistic function was deduced as the asymptotic limit. Microbial survival rate during hypervelocity meteoroid collisions was estimated by numerical analysis of impact phenomena with and without taking internal friction and plastic deformation of the colliding meteoroid and the target ground into consideration. Trajectory calculations of departing ejecta through the Martian atmosphere were conducted with taking account of aerodynamic deceleration and heating by the aid of computational fluid dynamic analysis. It is found that Mars ejecta smaller than 0.03 m in diameter hardly reach the Phobos orbit due to aerodynamic deceleration, or mostly sterilized due to significant aerodynamic heating even though they can reach the Phobos orbit and beyond. Finally, the baseline dataset of microbial density in Mars ejecta departing for Martian moons has been presented for the second part of our study., Comment: 24 pages, 12 figures, and 5 tables, accepted for publication in Life Sciences in Space Research, special issues on planetary protection

Linear and nonlinear waves in the near-surface plasma at Phobos and Deimos are considered. It is shown that the motion of the solar wind relative to photoelectrons and charged dust grains violates the isotropy of the electron distribution function in the near-surface plasma at the Martian satellites, which leads to the development of instability and excitation of high-frequency waves with frequencies in the range of Langmuir and electromagnetic waves. Moreover, the propagation of dust acoustic waves, which can be excited, e.g., in the terminator regions of the Martian satellites, is possible. Solutions corresponding to the parameters of the plasma–dust systems over the illuminated parts of the Phobos and Deimos surfaces are found in the form of dust acoustic solitons. The ranges of possible Mach numbers and soliton amplitudes are determined.

Current solar electric propulsion and launch vehicle technology allow sending multiple spacecraft to Mars simultaneously. For capture orbits with very high apoareion, the solar gravity perturbations deploy the spacecraft in vastly different areocentric orbits. This application requires knowledge of possible transfers and an efficient way to identify them; for example, a well-defined and easily accessed database of solutions. First, a method is developed to identify the required initial orbital elements and timing to target a final orbit, for a dynamical model ignoring the Martian eccentricity. This method can be applied to any planetary system with low heliocentric eccentricity. Second, the effect of Mars’ eccentricity and the corresponding time-dependence of solar distance are analyzed. This analysis requires a much larger number of numerical integrations. The research is therefore limited to placing bounds on the solution space. Third, this paper determines the way artificial neural networks can reduce the large number of required integrations by order(s) of magnitude while maintaining sufficient accuracy to enable preliminary transfer design. The neural networks enable the design of transfers between a low, near-polar orbit to Phobos and Deimos in an approximation of the eccentric model. These transfers are then validated in a higher fidelity ephemeris model.

The origin of the Martian moons, Phobos and Deimos, remains elusive. While the morphology and their cratered surfaces suggest an asteroidal origin1–3, capture has been questioned because of potential dynamical difficulties in achieving the current near-circular, near-equatorial orbits4,5. To circumvent this, in situ formation models have been proposed as alternatives6–9. Yet, explaining the present location of the moons on opposite sides of the synchronous radius, their small sizes and apparent compositional differences with Mars2 has proved challenging. Here, we combine geophysical and tidal-evolution modelling of a Mars–satellite system to propose that Phobos and Deimos originated from disintegration of a common progenitor that was possibly formed in situ. We show that tidal dissipation within a Mars–satellite system, enhanced by the physical libration of the satellite, circularizes the post-disrupted eccentric orbits in

The Martian Moons Exploration (MMX) mission of the Japan Aerospace Exploration Agency (JAXA) is scheduled to launch in 2024 and aims to be the world's first mission to return a sample from Phobos. For this, JAXA is developing the MMX sampler. There is a special interest in developing the corer shooting mechanism (C-Sampler) to acquire regolith, a robotic arm to position the core sampler and transfer the acquired regolith, and a sample transfer mechanism to move the regolith to a sample return capsule. This paper reports the system design of the MMX Sampler as well as the results of the tests for the corer sampling mechanism and the regolith conditions needed for effective penetration.

As human exploration endeavors begin to set sights beyond low Earth orbit to the surface of the Moon, exploration of the surface of Mars continues to serve as the “driving destination” to help focus development and research efforts. One Mars exploration strategy often discussed is the notion of utilizing the moons of Mars, namely Phobos, as an exploration destination prior to Mars surface missions. This strategy is sometimes advocated based on the premise that staging missions from Mars' moons as well as exploring the moons themselves would be less costly and risky. However, understanding potential advantages of Phobos staging and exploration must be done in the context of the overall end-to-end Mars surface exploration needs, goals, objectives, campaign approach, and systems required. This paper examines the strategic implications of utilizing the moons of Mars as a potential location for exploration of Mars. Operational concepts utilizing both Phobos and Mars orbital strategies will be examined to understand the architectural impacts of this staging strategy. The strategic implications of each operational concept are assessed to determine the overall key challenges and strategic links to other exploration destinations. Results from this analysis indicate that, if the objective is to conduct Mars surface missions, utilizing Phobos as an exploration destination adds little benefit toward the goal of exploration of Mars.

JAXA's Martian Moons eXploration Mission (MMX) includes the delivery of an exploration rover to the Mars moon Phobos in 2026, engineered by the Centre National d’Etudes Spatiales (CNES) and the German Aerospace Center (DLR). On Phobos, the gravity is about two thousand times lower than on Earth, which is why it is also called a milli-g environment. While the actual surface of Phobos is largely unknown, it is agreed within mission team that areas covered with regolith are to be expected. The design of the rover includes four actuated legs, with one rotational degree of freedom (DOF) each, and four individually driven, non-steerable wheels. The first task of the rover after landing on the surface of Phobos will be to deploy itself from its cruise configuration and to stand up on its wheels. Due to the rover dimensions, a full rotation of the legs and a wheel slip compensation are essential for this task. During operations, the locomotion system needs to provide drive and steer, as well as point turn abilities. Furthermore, the solar panel sun pointing, as well as the adjustment of scientific instruments, require that the rover aligns its body orientation and alters its body-to-ground distance. To satisfy all these requirements to the locomotion system of the MMX rover, appropriate locomotion control functions were developed. For driving curves and performing point turns, the skid steering method is applied and an “inching” locomotion mode for especially soft and steep terrain is adapted. In this inching locomotion, the front and rear wheel pair move alternately while the rover body moves up and down, which leads to enhanced traction performance compared to conventional driving in soft sand. This implies lower wheel slippage and sinkage resulting in a higher safety of the full rover system. The body orientation function, which is based on a kinematic control as well, provides a well coordinated movement and zero longitudinal slippage of the wheels during its execution. In this paper, a detailed description of the control algorithms is given and results from lab tests are presented and discussed. In a successful mission, these locomotion control functions will be the first ones actuating a wheeled mobile robot in milli-g environment.

Verification of thermal-mechanical-optical design for optical instruments in space exploration is highly significant due to large temperature variation and exposure to high shock and vibration levels. Such instruments must be completely robust to these harsh environments, as there are usually no options for realignment. The JAXA Martian Moons eXploration (MMX) Mission is set for launch in 2024 with main objectives to study the Martian moons, Deimos and Phobos. A rover will acquire for the first time Raman spectra of the Phobos surface using the Raman Spectrometer for MMX (RAX) developed at DLR. The Structural-Thermal-Model (STM) of RAX presented an early opportunity to evaluate the robustness of the instrument optical alignment to thermal and mechanical environments. An interferometric method implementing dummy objectives with cross hairs was developed to enable inline six-DOF measurements at critical places within the STM before development model (DM) optics were manufactured.

This paper summarizes the challenges of deep space planetary robotic-exploration missions, using the example of the DLR Autonomous Navigation Experiment within the MMX Rover project, and presents a preliminary design of the proposed solution to safe navigation of the MMX Rover on Pho-bose The MMX Rover, a joint contribution of the German Aerospace Center (DLR) and the Centre National dEtudes Spatiales (CNES) is part of the Martian Moons eXploration (MMX) Mission by the Japan Aerospace Exploration Agency (JAXA), whose mission objective is to understand the origin of the two Martian moons. The mission involves scientific data collection and a sample return from Phobos, the bigger of the two Martian moons. The mission is scheduled to launch in the third quarter of 2024. The MMX Rover will fly as a payload and will be jettisoned onto Phobos from a low altitude of about 40 metres. The rover has multiple objectives: terrain assessment to mitigate the risk for the sample-return approach of the spacecraft, exploration of the surface of Phobos and act as a scientific and technology demonstration platform. In this context, the Robotics and Mechatronics Institute, DLR, is preparing to perform an Autonomous Navigation Experiment as a technology demonstration to showcase the advantages of robot autonomy for exploring distant celestial bodies. If successful, the MMX Rover will be the first man-made object to land on and explore Phobos.

The origin of the two small prograde natural satellites of Mars may, or may not, be important in deciphering the early history of planet Mars. There have been many proposals for the origin of Phobos and Deimos but there is no generally accepted model for their origin. There is, however, substantial evidence for oblique impact of large bodies onto the surface of Mars in the retrograde (clock-wise) direction. These features suggest that a sizeable body, probably an asteroid, broke up in the vicinity of Mars and the disrupted debris, large and small, impacted along a great circle pattern on the martian surface. The proponents of this model also suggest that this orbiting retrograde satellite, before breaking apart, could have powered a martian core dynamo via tidal forces. I show the results of numerical simulations in which portions of asteroids could be gravitationally extracted from parent bodies in hyperbolic orbits passing through the weightlessness limit of Mars. The extracted bodies are then inserted into unstable orbits around Mars. These bodies eventually would impact onto the martian surface. Again, there is no consensus model for the origin of Phobos and Deimos.

GeMini is a high-resolution gamma-ray spectrometer designed for planetary-science exploration. GeMini serves as the basis for instruments being flown on three upcoming deep-space missions: NASA’s mission to the M-class asteroid (16) Psyche, the Japan Aerospace Exploration Agency sample-return mission to the moons of Mars, and NASA’s Dragonfly mission that will land on Saturn’s largest moon, Titan. These science missions require high-resolution spectroscopy in a low-power, low-mass, rugged design that can survive in a variety of environments. GeMini addresses these needs by providing a cryogenically cooled crystal of high-purity germanium that can operate with as little as 10 to 20 watts, depending on the implementation and mission, and has a mass of less than 2 kg. GeMini helps determine the elemental composition of planetary bodies by measuring gamma rays emitted from the surface. This paper describes the mechanical, thermal, and electrical design of GeMini as well as its performance. It also describes testing that was performed to validate the design with respect to launch loads and radiation damage. Although the basic design of GeMini is common to all three missions, each planetary body has unique environmental conditions and mission specifications. This paper concludes by describing these upcoming missions and how GeMini is customized for each.

Mass-spring model simulations are used to investigate past spin states of a viscoelastic Phobos and Deimos. From an initially tidally locked state, we find crossing of a spin-orbit resonance with Mars or a mean motion resonance with each other does not excite tumbling in Phobos or Deimos. However, once tumbling our simulations show that these moons can remain so for an extended period and during this time their orbital eccentricity can be substantially reduced. We attribute the tendency for simulations of an initially tumbling viscoelastic body to drop into spin-synchronous state at very low eccentricity to the insensitivity of the tumbling chaotic zone volume to eccentricity. After a tumbling body enters the spin synchronous resonance, it can exhibit long lived non-principal axis rotation and this too can prolong the period of time with enhanced tidally generated energy dissipation. The low orbital eccentricities of Phobos and Deimos could in part be due to spin excitation by nearly catastrophic impacts rather than tidal evolution following orbital resonance excitation.

Phobos and Deimos occupy unique positions both scientifically and programmatically on the road to the exploration of the solar system. Japan Aerospace Exploration Agency (JAXA) plans a Phobos sample return mission (MMX: Martian Moons eXploration). The MMX spacecraft is scheduled to be launched in 2024, orbit both Phobos and Deimos (multiple flybys), and retrieve and return >10 g of Phobos regolith back to Earth in 2029. The Phobos regolith represents a mixture of endogenous Phobos building blocks and exogenous materials that contain solar system projectiles (e.g., interplanetary dust particles and coarser materials) and ejecta from Mars and Deimos. Under the condition that the representativeness of the sampling site(s) is guaranteed by remote sensing observations in the geologic context of Phobos, laboratory analysis (e.g., mineralogy, bulk composition, O-Cr-Ti isotopic systematics, and radiometric dating) of the returned sample will provide crucial information about the moon’s origin: capture of an asteroid or in-situ formation by a giant impact. If Phobos proves to be a captured object, isotopic compositions of volatile elements (e.g., D/H,13C/12C,15N/14N) in inorganic and organic materials will shed light on both organic-mineral-water/ice interactions in a primitive rocky body originally formed in the outer solar system and the delivery process of water and organics into the inner rocky planets.

The origin of the natural satellites or moons of the solar system is as challenging to unravel as the formation of the planets. Before the start of the space probe exploration era, this topic of planetary science was restricted to telescopic observations, which limited the possibility of testing different formation scenarios. This era has considerably boosted this topic of research, particularly after the Apollo missions returned samples from the Moon’s surface to Earth. Observations from subsequent deep space missions such as Viking 1 and 2 Orbiters, Voyager 1 and 2, Phobos-2, Galileo, Cassini-Huygens, and the most recent Mars orbiters such as Mars Express, as well as from the Hubble space telescope, have served to intensify research in this area. Each moon system has its own specificities, with different origins and histories. It is widely accepted that the Earth’s Moon formed after a giant collision between the proto-Earth and a body similar in size to Mars. The Galilean moons of Jupiter, on the other hand, appear to have formed by accretion in a circum-Jovian disk, while smaller, irregularly shaped satellites were probably captured by the giant planet. The small and medium-sized Saturnian moons may have formed from the rings encircling the planet. Among the terrestrial planets, Mercury and Venus have no moons, the Earth has a single large moon, and Mars has two very small satellites. This raises some challenging questions: What processes can lead to moon formation around terrestrial planets and what parameters determine the possible outcomes, such as the number and size of moons? The answer to such fundamental questions necessarily entails a thorough understanding of the formation of the Martian system and may have relevance to the possible existence of (exo)moons orbiting exoplanets. The formation of such exomoons is of great importance as they could influence conditions for habitability or for maintaining life over long periods of time on the surface of Earth-like exoplanets, for example by limiting the variations of the orientation of the planet’s rotation axis and thus preventing frequent changes of its climate. Our current knowledge concerning the origin of Phobos and Deimos has been acquired from observational data as well as theoretical work. Early observations led to the idea that the two satellites were captured asteroids but this created difficulties in reconciling the current orbits of Phobos and Deimos with those of captured bodies, hence suggesting the need for an alternative theory. A giant-impact scenario provides a description of how moons similar to Phobos and Deimos can be formed in orbits similar to those observed today. This scenario also restricts the range of possible composition of the two moons, providing a motivation for future missions that aim for the first time to bring material from the Martian system back to Earth.

MMX (Martian Moons eXploration) is a robotic sample return mission of JAXA (Japan Aerospace Exploration Agency), CNES (Centre National d' Etudes Spatiales), and DLR (German Aerospace Center) with the launch planed for 2024. The mission aims to answer the question of the origin of Phobos and Deimos, which will also help to understand the material transport in the earliest period of our solar system, and of how was water brought to Earth. Besides JAXA's MMX mothership, which is responsible for sampling and sample return to Earth, a small rover which is built by CNES and DLR to land on Phobos for in-situ measurements, similar to MASCOT (Mobile Asteroid Surface Scout) on Ryugu. The MMX rover is a four-wheel driven autonomous system with a size of 41 cm × 37 cm × 30 cm and a weight of approximately 25 kg. Multiple science instruments and cameras are integrated in the rover body. The rover body has the form of a rectangular box. Attached at the sides are four legs with one wheel per leg. When the rover is detached from the mothership, the legs are folded together at the side of the rover body. When the rover has landed passively (no parachute or braking rockets) on Phobos, the legs are autonomously maneuvered to bring the rover in an upright orientation. One Phobos day lasts 7.65 earth hours, which yields about 300 extreme temperature cycles for the total mission time of three earth months. These cycles and the wide span of surface temperature between day and night are the main design drivers for the rover. This paper gives a detailed view on the development of the MMX rover locomotion subsystem.

The goal of the JAXA's Martian Moons Exploration (MMX) mission is to explore the two moons of Mars, Phobos and Deimos, and return samples from the surface of Phobos. Honeybee Robotics is designing and fabricating a NASA-provided Pneumatic Sampler, or P-Sampler, that would capture surface material from Phobos using a pneumatic sampling approach. The P-Sampler will be mounted along a leg of the MMX lander. The sampling head of the P-sampler utilizes two sets of sampling nozzles: one set of nozzles pointed directly at the surface to kick-up and loft material into the sampling head, and a second set of nozzles to direct the oncoming material into the sample return canister further up the lander leg. A robotic arm mounted underneath the lander will then remove the sample canister and place it inside the sample return capsule. Several iterations of the P-Sampler have been designed and tested inside a vacuum chamber with Phobos analog material. In all tests, the P-Sampler successfully acquired sample, even in an extreme scenario where the sampling head was mounted 10 cm above the surface covered with gravel.

The origins of Phobos and Deimos are uncertain; both are so space weathered that their surface compositions are difficult to determine using spectral reflectance measurements. We show how the winter temperatures and associated conditions in the polar regions of Phobos could make the regolith susceptible to space weathering from dielectric breakdown caused by solar energetic particles (SEPs). During SEP events, charged particles accumulate throughout the top ∼1 mm of the regolith, which has low conductivity, and create subsurface electric fields that act to dissipate any net buildup of charge. The faster the net charge accumulates, the larger the electric field needed to dissipate it. If the magnitude of the subsurface electric field exceeds ∼ 10 6 V m−1, then dielectric breakdown is likely. This process rapidly dissipates the buildup of charge by vaporizing electrically conducting channels through the regolith. Dielectric breakdown is expected to be more prevalent in colder regions, where the electrical conductivity of the regolith is lower and the dissipation of charge is consequently slower. If the regolith on Phobos is made of silicates, or possibly phyllosilicates, we predict that dielectric breakdown weathering has melted or vaporized 5–10% of the impact gardened regolith in the polar regions, although this percentage depends on how long the regolith has been exposed to SEPs. This, in addition to the long exposure time of the regolith to other forms of space weathering, may help explain why both Phobos and Deimos are highly space weathered compared to other airless bodies in the Solar System, such as Earth’s Moon.

Phobos and Deimos are the only natural satellites of the terrestrial planets, other than our Moon. Despite decades of revolutionary Mars exploration and plans to send humans to the surface of Mars in the 2030’s, there are many strategic knowledge gaps regarding the moons of Mars, specifically regarding the origin and evolution of these bodies. Addressing those knowledge gaps is itself important, while it can also be seen that Phobos and Deimos are positioned to support martian surface operations as a staging point for future human exploration. Here, we present a science exploration architecture that seeks to address the role of Phobos and Deimos in the future exploration of Mars. Phobos and Deimos are potentially valuable destinations, providing a wealth of science return, as well as telecommunications capabilities, resource utilization, radiation protection, transportation and operations infrastructure, and may have an influence on the path of the martian exploration program. A human mission to the moons of Mars would maintain programmatic focus and public support, while serving as a catalyst for a successful human mission to the surface of Mars.

The long-term goal of enabling human exploration of the Moon and Mars drives International space exploration plans. Robotic space missions must therefore develop and demonstrate the feasibility and robustness of the enabling technologies and capabilities. The Phobos Sample Return mission is a candidate mission of the Mars Robotic Exploration Preparation programme. Its objective is to acquire and return a sample from the Mars moon Phobos. The main science goal of this mission will be to understand the formation of the Martian moons Phobos and Deimos and acquire further data on the evolution of the solar system. From a technology standpoint, it would be a big step forward in the development of many technologies, ranging from low-gravity body landing capabilities to Earth re-entry of samples from deep space, from semi-autonomous robotic acquisition of surface samples to sample preservation and further analysis in dedicated ground laboratories. Thales Alenia Space represents one of two industrial contractors studying the mission to Phase A level. This phase involves investigation of all aspects of the mission and spacecraft design to ensure its feasibility and robustness. The planned launch date for the mission is between 2025 and 2027. The Ariane 5 ECA launch vehicle will be launched from Kourou. A chemical propulsion module will transfer the spacecraft composite to the Martian system, and will then be separated at Phobos. A full characterization campaign of Phobos at different altitudes from orbit will follow. This will include quasi-satellite orbits and flybys, using a payload suite of cameras and spectrometers. When the preferred landing site is identified, a controlled descent and touchdown onto the surface of Phobos will be performed, with a touchdown accuracy of 50 m. A robotic arm and sampling mechanism will obtain and verify a sample of surface regolith, and insert it into the Earth re-entry capsule. Part of the Spacecraft will return to the Earth from Phobos and deliver the re-entry capsule to the Earth’s atmosphere. The capsule will perform a fully passive Earth entry, descent and landing in Woomera, Australia. It will then be recovered and transferred to a sample curation facility for sample extraction and analysis. This paper summarises the results of the Thales Alenia Space Phobos Sample Return mission and spacecraft design, with a focus on the key elements and mass drivers.

In order to determine whether Martian dust belts (ring or torus) actually exist and, if so, to determine the characteristics of the dust, we propose a Circum-Martian Dust Monitor (CMDM) to be deployed on the Martian Moons Exploration (MMX) project, in which JAXA plans to launch the spacecraft in 2024, investigate Phobos and Deimos, and return samples back to Earth. The CMDM is a newly developed instrument that is an impact dust detector. It weighs only 650 g and has a sensor aperture area of ∼ 1 m2, according to the conceptual design study. Detectable velocities (v) range from 0.5 km/s to more than 70 km/s, which will cover all possible dust particles: circummartian (low v), interplanetary (mid v), and interstellar (high v) particles. The measurable mass ranges from 1.3 × 10−9 g to 7.8 × 10−7 g at v = 0.5 km/s. Since the MMX spacecraft will take a quasi-circular, prograde orbit around Mars, the CMDM will be able to investigate particles from Phobos and Deimos with relative velocities lower than 1 km/s. Therefore, the CMDM will be able to determine whether or not a confined dust ring exists along Phobos' orbit and whether an extended dust torus exists along Deimos' orbit. It may also be able to clarify whether or not any such ring or torus are self-sustained.

A number of planetary spacecraft missions have carried instruments with sensors covering the ultraviolet (UV) wavelength range. However, there exists a general lack of relevant UV reflectance laboratory data to compare against these planetary surface remote sensing observations in order to make confident material identifications. To address this need, we have systematically analyzed reflectance spectra of carbonaceous materials in the 200–500 nm spectral range, and found spectral-compositional-structural relationships that suggest this wavelength region could distinguish between otherwise difficult-to-identify carbon phases. In particular (and by analogy with the infrared spectral region), large changes over short wavelength intervals in the refractive indices associated with the trigonal sp2 π–π* transition of carbon can lead to Fresnel peaks and Christiansen-like features in reflectance. Previous studies extending to shorter wavelengths also show that anomalous dispersion caused by the σ–σ* transition associated with both the trigonal sp2 and tetrahedral sp3 sites causes these features below λ = 200 nm. The peak wavelength positions and shapes of π–π* and σ–σ* features contain information on sp3/sp2, structure, crystallinity, and powder grain size. A brief comparison with existing observational data indicates that the carbon fraction of the surface of Mercury is likely amorphous and submicroscopic, as is that on the surface of the martian satellites Phobos and Deimos, and possibly comet 67P/Churyumov–Gerasimenko, while further coordinated observations and laboratory experiments should refine these feature assignments and compositional hypotheses. The new laboratory diffuse reflectance data reported here provide an important new resource for interpreting UV reflectance measurements from planetary surfaces throughout the solar system, and confirm that the UV can be rich in important spectral information.

Accepted: 2018-03-12, 資料番号: SA1170290000

The International Astronomical Union (IAU) defines planet and satellite coordinate systems relative to their axis of rotation and the angle about that axis. The rotational elements of the bodies are the right ascension and declination of the rotation axis in the International Celestial Reference Frame and the rotation angle, W, measured easterly along the body's equator. The IAU specifies the location of the body's prime meridian by providing a value for W at epoch J2000. We provide new trigonometric series representations of the rotational elements of Mars and its satellites, Phobos and Deimos. The series for Mars are from a least squares fit to the rotation model used to orient the Martian gravity field. The series for the satellites are from a least squares fit to rotation models developed in accordance with IAU conventions from recent ephemerides.

We measured near-infrared (NIR) reflectance spectra of Phobos and Deimos, using the prism (0.7–2.52 μm) and long-wavelength cross dispersed (LXD: 1.9–4.2 μm) modes of NASA Infrared Telescope Facility (IRTF)’s SpeX instrument. The goal of this study is to investigate the surface composition of Phobos and Deimos and search for any mineralogical absorption signatures that may be present on their surfaces, especially in the LXD spectral range. Prism spectra of Phobos showed significant slope variation at shorter wavelengths (λ

Phobos is one of the two moons of Mars, the only other terrestrial planet to have companions. In spite of certain common orbital characteristics between Earth’s Moon and Phobos, such as almost circular, low-inclination, and synchronous orbits, the origin of the Martian moons remains to be understood. This unsettled state of affairs reflects a scarcity of data pertinent to its interior structure and bulk composition, both of which hold the key to solving the question of the provenance of the satellites. Drawing on the importance of interior structure as a means of providing further constraints on this problem, we construct a series of models of the interior of Phobos in accordance with current observations and determine their tidal deformation. The models include a homogeneous body, ice-rock mixtures, models with positive and negative density gradients, and layered models. To compute the deformation of Phobos precisely, we solve the three-dimensional elastostatic problem to obtain the full displacement field. For this, we rely on a higher-order spectral-element method and to account for a correct representation of shape and resulting displacement field, we accurately mesh the figure of Phobos by employing the digital terrain model of Willner et al. (2014). To enable us to further distinguish between models, we also rely on currently available geophysical data (e.g., magnitude of libration in longitude, mean density, gravity field, and moments of inertia). Our results show that the homogeneous, ice-rock mixture, and negative density gradient models are largely degenerate and therefore difficult to separate, but that models with a density increase with depth can be differentiated from the former model families. From a purely deformational point of view, we find that for positive gradient and layered models, the largest deformation occurs on the rim of the Stickney crater, rather than immediately at the sub-Mars point on Phobos, as in the case of the other models, where tidal forces are largest. These observations will be of considerable interest and should provide important anchoring points for the future exploration of Phobos as envisaged with the Martian Moons Exploration mission.