Martian Moons Research Articles

Low-fuel transfers from Mars to quasi-satellite orbits around Phobos exploiting manifolds of tori

Quasi-satellite orbits (QSOs) are considered by JAXA’s MMX mission, in which CNES is involved, for the scientific observation of the Martian moon Phobos prior to landing and sample return operations. These periodic orbits, originally defined in the Mars-Phobos circular restricted three-body problem, generically lose periodicity once the eccentricity of Phobos’ orbit is taken into account. In this case, QSOs are replaced by quasi-periodic tori. Recent work on MMX project includes, among many others, station-keeping strategies around QSOs exploiting invariant tori in the elliptic Hill problem. In the present paper, a resonant QSO will be first computed in the Mars-Phobos circular restricted three-body problem. Then, by continuation on the eccentricity of the secondary, this QSO will be converted into a periodic resonant QSO in the Mars-Phobos elliptic restricted three-body problem. The latter problem is more precise than the Hill problem at far distance from the secondary and thus more adapted to handle Mars-Phobos transfers. Notice that considering resonant orbits enables to preserve the periodicity of the QSOs when the eccentricity is nonzero. Then, a family of invariant tori surrounding the resonant QSO in the Elliptic Restricted Three-Body Problem will be obtained by continuation on the frequency. In the next step, stable invariant manifolds emanating from the tori will be computed. Finally, two-impulse transfers between a parking orbit around Mars and the tori surrounding the QSO will be presented with the objective to minimize the total velocity increment. Interesting transfer trajectories will be shown allowing for a ballistic approach to Phobos. These trajectories lead to a reduction in the total velocity increment in comparison with classical Mars to QSOs transfers. Here, instead of targeting directly the resonant QSO, the spacecraft will reach first an invariant manifold before coasting along this manifold until encountering a torus surrounding the QSO. Thus, the spacecraft will reach a quasi-periodic QSO inside the torus that is close to the periodic resonant QSO.

Modelling cometary meteoroid stream traverses of the Martian Moons eXploration (MMX) spacecraft en route to Phobos

The Martian Moons Exploration (MMX) spacecraft is a JAXA mission to Mars and its moons Phobos and Deimos. MMX will be equipped with the Circum-Martian Dust Monitor (CMDM) which is a newly developed light-weight (mathrm {650,g}) large area (1,mathrm {m}^{2}) dust impact detector. Cometary meteoroid streams (also referred to as trails) exist along the orbits of comets, forming fine structures of the interplanetary dust cloud. The streams consist predominantly of the largest cometary particles (with sizes of approximately 100,mu mathrm { m} to 1 cm) which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun. The Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model is a new and recently published universal model for cometary meteoroid streams in the inner Solar System. We use IMEX to study the detection conditions of cometary dust stream particles with CMDM during the MMX mission in the time period 2024 to 2028. The model predicts traverses of 12 cometary meteoroid streams with fluxes of 100,mu mathrm { m} and bigger particles of at least 10^{-3},mathrm {m}^{-2},mathrm {day}^{-1} during a total time period of approximately 90 days. The highest flux of 0.15,mathrm {m}^{-2},mathrm {day}^{-1} is predicted for comet 114P/Wiseman-Skiff in October 2026. With its large detection area and high sensitivity CMDM will be able to detect cometary meteoroid streams en route to Phobos. Our simulation results for the Mars orbital phase of MMX also predict the occurrence of meteor showers in the Martian atmosphere which may be observable from the Martian surface with cameras on board landers or rovers. Finally, the IMEX model can be used to study the impact hazards imposed by meteoroid impacts onto large-area spacecraft structures that will be particularly necessary for crewed deep space missions.

Dynamical evidence for Phobos and Deimos as remnants of a disrupted common progenitor

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 <2.7 Gyr and makes Phobos descend to its present orbit from its point of origin close to or above the synchronous orbit. Our estimate for Phobos’s maximal tidal lifetime is considerably less than the age of Mars, indicating that it is unlikely to have originated alongside Mars. Deimos initially moved inwards, but never transcended the co-rotation radius because of insufficient eccentricity and therefore insufficient tidal dissipation. Whereas Deimos is very slowly receding from Mars, Phobos will continue to spiral towards and either impact with Mars or become tidally disrupted on reaching the Roche limit in ≲39 Myr. Tidal-evolution modelling, combined with new geophysical constraints of Mars and viscoelastic laboratory measurements, suggests that the two Martian moons have a common progenitor that was disrupted between 1 and 2.7 billion years ago.

Phobos regolith simulants PGI-1 and PCA-1

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.

Transfers around Phobos via bifurcated retrograde orbits: Applications to Martian Moons eXploration mission

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 ΔV 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.

Experimental Insights Into Space Weathering of Phobos: Laboratory Investigation of Sputtering by Atomic and Molecular Planetary Ions

AbstractInvestigating the space weathering of the Martian moon Phobos represents an important step toward understanding the development from its origin to its present‐day appearance. Depending on Phobos’ orbital position, its surface is continuously sputtered by the solar wind and planetary ions that originate in the Martian atmosphere. Based on Mars Atmosphere and Volatile Evolution measurements, it has been proposed that sputtering by planetary O+ and O2+ ions dominates in the Martian tail region, where the planet mostly shadows Phobos from the solar wind. In these models, uncertainties for sputtering yield inputs still exist due to the lack of sufficient analog experiments. Therefore, sputtering measurements with O+, O2+, C+, and CO2+ ions between 1 and 5 keV were performed using augite samples as Phobos analogs. The experimental results for O+ irradiations show smaller mass changes than predicted by SDTrimSP simulations, which probably can be attributed to O implantation enabled by the Fe content of the target. Sputtering with O2+ and CO2+ in the low keV range shows no deviations in the sputtering yields attributable to molecular effects. Therefore, CO2+ ions will most likely be negligible for the sputtering of Phobos according to the current understanding of ion fluxes on the Martian moon. Ultimately, our experiments suggest that the sputtering contribution on Phobos by O ions is about 50% smaller than previously assumed. This does not change the qualitative outcome from previous modeling stating that planetary O ions are by far the dominant sputtering contribution on Phobos in the Martian tail region.

German Aerospace Center's advanced robotic technology for future lunar scientific missions.

The Earth's moon is currently an object of interest of many space agencies for unmanned robotic missions within this decade. Besides future prospects for building lunar gateways as support to human space flight, the Moon is an attractive location for scientific purposes. Not only will its study give insight on the foundations of the Solar System but also its location, uncontaminated by the Earth's ionosphere, represents a vantage point for the observation of the Sun and planetary bodies outside the Solar System. Lunar exploration has been traditionally conducted by means of single-agent robotic assets, which is a limiting factor for the return of scientific missions. The German Aerospace Center (DLR) is developing fundamental technologies towards increased autonomy of robotic explorers to fulfil more complex mission tasks through cooperation. This paper presents an overview of past, present and future activities of DLR towards highly autonomous systems for scientific missions targeting the Moon and other planetary bodies. The heritage from the Mobile Asteroid Scout (MASCOT), developed jointly by DLR and CNES and deployed on asteroid Ryugu on 3 October 2018 from JAXA's Hayabusa2 spacecraft, inspired the development of novel core technologies towards higher efficiency in planetary exploration. Together with the lessons learnt from the ROBEX project (2012–2017), where a mobile robot autonomously deployed seismic sensors at a Moon analogue site, this experience is shaping the future steps towards more complex space missions. They include the development of a mobile rover for JAXA's Martian Moons eXploration (MMX) in 2024 as well as demonstrations of novel multi-robot technologies at a Moon analogue site on the volcano Mt Etna in the ARCHES project. Within ARCHES, a demonstration mission is planned from the 14 June to 10 July 2021,1 during which heterogeneous teams of robots will autonomously conduct geological and mineralogical analysis experiments and deploy an array of low-frequency antennas to measure Jovian and solar bursts.This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades'.

Configuration of the Martian dust rings: shapes, densities, and size distributions from direct integrations of particle trajectories

ABSTRACTIt is expected since the early 1970s that tenuous dust rings are formed by grains ejected from the Martian moons Phobos and Deimos by impacts of hypervelocity interplanetary projectiles. In this paper, we perform direct numerical integrations of a large number of dust particles originating from Phobos and Deimos. In the numerical simulations, the most relevant forces acting on the dust are included: Martian gravity with spherical harmonics up to fifth degree and fifth order, gravitational perturbations from the Sun, Phobos, and Deimos, solar radiation pressure, as well as the Poynting–Robertson drag. In order to obtain the ring configuration, simulation results of various grain sizes ranging from submicrometres to 100 μm are averaged over a specified initial mass distribution of ejecta. We find that for the Phobos ring grains smaller than about 2 μm are dominant; while the Deimos ring is dominated by dust in the size range of about 5–20 μm. The asymmetries, number densities, and geometric optical depths of the rings are quantified from simulations. The results are compared with the upper limits of the optical depth inferred from Hubble observations. We compare to previous work and discuss the uncertainties of the models.

Design and sensitivity analysis of spacecraft swarms for planetary moon reconnaissance through co-orbits

This work presents an automated mission design architecture for global surface mapping missions to planetary moons. Such missions need to address three important challenges: virtually absent spheres of influence, tidal locking, and self-shadowing. Therefore, a complex task such as global surface coverage is better handled using the swarm approach. The design of a swarm mission for such a dynamic environment is challenging. For this reason, we developed the Integrated Design Engineering and Automation of Swarms (IDEAS) software to facilitate the automated end-to-end design of swarm mission concepts. Specifically, it will use a sub-module known as the Automated Swarm Designer module to find optimal swarm configurations suited for a given mission. In our previous work, we developed the Automated Swarm Design module to find swarm configurations for asteroid mapping operations. Here, we will evaluate the capability of the Automated Swarm designer module to design missions to planetary moons, and also examine the sensitivity of the generated optimal design to various perturbations. Specifically, we explore the design space of resonant co-orbits where the spacecraft will have planned periodic encounters with the planetary moon due to the natural dynamics. The swarm will be deployed on resonant co-orbits using an aeroassist from the central planet. the maneuver cost with this deployment is broken down into two maneuvers: a planar orbit insertion maneuver using aerobraking, and an orientation change maneuver required to facilitate a planar orbit capture. The design space of such missions is examined, and the principles are illustrated using numerical case studies of a global surface mapping mission to the Martian moon Deimos. Using the described principles, a spacecraft swarm mission to map 90 % of the surface of Deimos is designed. The designed swarm consists of 5 spacecraft, which have a maximum estimated orientation change Δv of 1.97 km/s, and a worst-case orbit insertion Δv of 0.848 km/s if aerobraking is used. Overall implications on the mission, such as fuel requirements, and aerobraking timespans are then studied. Finally, the sensitivities of the designed swarm to different perturbations are studied, and peak disturbances that lead to coverage deterioration below a threshold of 80 % are noted.

Extended Robust Planetary Orbit Insertion Method Under Probabilistic Uncertainties

Planetary orbit insertion maneuver is one of the most critical events in deep space exploration missions. Once the spacecraft fails to decelerate enough to stay in the planetary orbit, it escapes from the vicinity of the planet. In some cases, such as the Akatsuki mission of Japan Aerospace Exploration Agency (JAXA), a feasible recovery trajectory was found after an engine malfunction; however, in many cases, the mission may fail because the spacecraft will end its mission life before reencountering the planet. To mitigate the risk, researchers have studied robust orbit insertion strategies, which reduce the total probabilistic by sacrificing nominal and shorten the flight time to reencounter the planet. Previous studies consider the possibility that planetary orbit insertion fails completely and use resonant trajectories as the recovery trajectories. This paper extends the robust orbit insertion method by implementing V-infinity leveraging transfers as the recovery trajectories. This extension enables to treat general probability models that describe the partial failures of orbit insertion maneuvers. The numerical example of JAXA’s Martian Moons Exploration mission shows that the proposed method enhances performance, namely, the expected and , as well as robustness.

Automated design architectures for co-orbiting spacecraft swarms for planetary moon mapping

This work describes the design and optimization of spacecraft swarm missions to meet spatial and temporal visual mapping requirements of missions to planetary moons, using resonant co-orbits. The algorithms described here are a part of Integrated Design Engineering and Automation of Swarms (IDEAS), a spacecraft swarm mission design software that automates the design trajectories, swarm, and spacecraft behaviors in the mission. In the current work, we focus on the swarm design and optimization features of IDEAS, while showing the interaction between the different design modules. In the design segment, we consider the coverage requirements of two general planetary moon mapping missions: global surface mapping and region of interest observation. The configuration of the swarm co-orbits for the two missions is described, where the participating spacecraft have resonant encounters with the moon on their orbital apoapsis. We relate the swarm design to trajectory design through the orbit insertion maneuver performed on the interplanetary trajectory using aero-braking. We then present algorithms to model visual coverage, and collision avoidance in the swarm. To demonstrate the interaction between different design modules, we relate the trajectory and swarm to spacecraft design through fuel mass, and mission cost estimations using preliminary models. In the optimization segment, we formulate the trajectory and swarm design optimizations for the two missions as Mixed Integer Nonlinear Programming (MINLP) problems. In the current work, we use Genetic Algorithm as the primary optimization solver. However, we also use the Particle Swarm Optimizer to compare the optimizer performance. Finally, the algorithms described here are demonstrated through numerical case studies, where the two visual mapping missions are designed to explore the Martian moon Deimos.

Simulating microbial processes in extraterrestrial, aqueous environments

Finding evidence of life elsewhere in the Solar System is dependent on understanding biotic processes that could occur within potentially habitable environments. Here, we describe a suite of high-pressure flow-through reactors that have been developed to investigate biotic and abiotic processes within simulated sub-surface martian and icy moon environments.

Size matters - The shell lander concept for exploring medium-size airless bodies

Once addressed as a side topic in planetary exploration, the investigation of small solar system bodies has now become one of the corner stones in the international science community in order to study the formation of the solar system and the evolution of life within. For rendezvous spacecraft, small carry-on landers have proven to be valuable assets, and to have a positive impact on the overall mission cost, by avoiding additional complexity of the main satellite and transferring the risk of close surface maneuvers entirely or at least to some extend to an independent deployable system. However, carry-on landers have been designed currently to land on very small bodies only, but medium-size class objects between diameters of 10–50 km are of great interest as well. In this paper we classify carry-on landers with respect to their touchdown and operational strategy, evaluate the constraints of ballistic deployments for different target bodies as well as identify the niche for using simple honeycomb impact dampers compared to optional retro-propulsion systems. Further, we introduce the system design of an attitude-stabilized Shell Lander using a generic instrument carrier attached to a single ejectable crash-pad with stabilizing capability to protect the instrument carrier from structural damage, limit internal shock loads for sensitive payloads as well as reduce the amount of bounces on the surface. Finally, we present a mission architecture for a reference case to the Martian moon Phobos as well as provide a proof of concept based on laboratory impact tests and a multi-body simulation to analyze touchdown dynamics including terrain interaction, shell-shedding and bouncing.

Tracking neighboring quasi-satellite orbits around Phobos

We consider the orbital maintenance problem on a quasi-satellite orbit about the Martian moon, Phobos. The orbit is computed using a high-fidelity ephemeris model so that the major sources of disturbances are due to measurement error. Two types of orbit maintenance schemes are considered. The first is based on asymptotically tracking the desired trajectory and the second is based on stabilizing to the manifold of trajectories that share the same Jacobi constant as the reference trajectory. The latter can be done because trajectories with the same Jacobi constant are in the neighborhood of one another. The results show that the trajectory-tracking scheme has lower fuel consumption when tracking must be precise and that the approach of stabilizing to a manifold has better fuel consumption at the expense of tracking.

Experimental Study to Determine the Best Compression Ratio of High-Resolution Images of Small Bodies for the Martian Moons eXploration Mission

Experimental Study to Determine the Best Compression Ratio of High-Resolution Images of Small Bodies for the Martian Moons eXploration Mission

Transport of impact ejecta from Mars to its moons as a means to reveal Martian history

Throughout the history of the solar system, Mars has experienced continuous asteroidal impacts. These impacts have produced impact-generated Mars ejecta, and a fraction of this debris is delivered to Earth as Martian meteorites. Another fraction of the ejecta is delivered to the moons of Mars, Phobos and Deimos. Here, we studied the amount and condition of recent delivery of impact ejecta from Mars to its moons. Using state-of-the-art numerical approaches, we report, for the first time, that materials delivered from Mars to its moons are physically and chemically different from the Martian meteorites, which are all igneous rocks with a limited range of ages. We show that Mars ejecta mixed in the regolith of its moons potentially covers all its geological eras and consists of all types of rocks, from sedimentary to igneous. A Martian moons sample-return mission will bring such materials back to Earth, and the samples will provide a wealth of “time-resolved” geochemical information about the evolution of Martian surface environments.

Measuring the Elemental Composition of Phobos: The Mars‐moon Exploration with GAmma rays and NEutrons (MEGANE) Investigation for the Martian Moons eXploration (MMX) Mission

AbstractThe Mars‐moon Exploration with GAmma rays and NEutrons (MEGANE) investigation will use gamma‐ray and neutron spectroscopy to measure the elemental composition of Mars' moon Phobos. MEGANE is part of the Japanese Martian Moons eXploration (MMX) mission that will make comprehensive remote sensing measurements of both of Mars' moons Phobos and Deimos. MMX will also return to Earth regolith samples of Phobos. The science goals of the MEGANE investigation mirror those of the MMX mission. MEGANE will use elemental composition measurements to determine if Phobos is a captured asteroid or the end result of a giant impact event on Mars, study Phobos surface processes, provide reconnaissance to support the sample site selection, and supply compositional context for the returned samples. To accomplish its measurements, MEGANE will use a high‐purity Ge gamma‐ray spectrometer (GRS), and a neutron spectrometer (NS) that consists of two3He gas proportional neutron sensors. The GRS derives heritage from similar instruments from NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission and the Psyche mission that is currently in development; the NS is based on similar instruments used for NASA's Lunar Prospector and Psyche missions.

The second-degree gravity coefficients of Phobos from two Mars Express flybys

ABSTRACT Several close spacecraft flybys of Phobos have been performed over the past 40 yr in order to determine the gravity field of this tiny Martian moon. In this work, the second-degree coefficients of the gravity field of Phobos were derived from the radio tracking data of two combined Mars Express flybys (2010 and 2013), by applying a least squares regularized inverse technique, that introduces as an a priori the gravity field retrieved from a shape model based on constant density hypothesis. A gravitational mass estimate of $(7.0765\pm 0.0075)\times 10^5 \, \mathrm{m^3\, s}^{-2}$ and second-degree gravity coefficients C20 = −0.1378 ± 0.0348 and C22 = 0.0166 ± 0.0153(3σ) were derived. The estimated C20 value, in contrast to the value of C20 computed from the shape model under the constant density assumption, supports an inhomogeneous distribution inside Phobos at a confidence interval of 95 per cent (1.96σ). This result indicates a denser mass in the equatorial region or lighter mass in polar areas.

Electrochemical Interfacial Phenomena Under Microgravity

Electrochemical Processing under extreme conditions like reduced gravity, strong cosmic ray irradiation and magnetic fields should be well designed in the era of Gateway after ISS. JAXA’s “HAYABUSA” satellite project of Successful Sample Return from Asteroid “Itokawa” was achieved by newly developed Ion Engine and well controlled life-cycling of LIB. Now, HAYABUSA 2” is approaching to “Ryugu” asteroid by Pin-point Landing supported with Robotics & AI Image Learning (Self Controlled Driving). Moreover, Manned Rover operation plan toward Lunar Hydrogen Energy System in 2029 was announced by JAXA-TOYOTA last March. CO2 Reduction for Life Supporting System must be reasonably combined. HERACLES (Human Enhanced Robotic Architecture for Lunar Exploration and Science) and MMX (Martian Moons eXploration) shall be further planned. High Temp. Molten Oxide Electrolysis with Inert Anode are engaged as ISRU. One of the fundamental subjects common in designing the energy conversion and storage devices in space engineering is to well control the electrochemical interfacial phenomena among three Gas/Liquid(Aqueous or Molten Oxide)/Solid(Metal or Solid Oxide) phases under reduced gravity and magnetic field. Experimental studies in Drop Tower, a parabolic flight and University Laboratory(1-G) to focus the wettability effects on these phenomena were reported over last 30 years1-10). O2 bubble evolution behavior on Pt electrode modified by thiol SAM was monitored during alkaline water electrolysis under μ-G with a high speed video camera. Single bubble measurements on microwire electrode was additionally engaged. The latter revealed three-step processes involving (1) the nucleation and formation of supersaturated layer of dissolved O2 gas followed by (2) a rapid growth depending on the gas diffusion process and finally (3)a stable growth where its growth rate is dominated by bubble configuration depending on the contact angle. Moreover, the correlation of multiple gas bubble observation with electrochemical data and surface coverage on the plate electrode reinforces the importance of wettability in determining two phase flow motion and energy consumption during electrolysis. The degree of supersaturation of dissolved gas on hydrophilic/hydrophobic electrode surface in aqueous solution and molten salt are also studies. They are compared to 1-G experiments in order to newly enlighten the matured gas electrode concepts. “Electrochemical Laboratory in ISS & Gateway” should be constructed with Space Agencies.

Planetary protection classification of samples returned from the martian moons: Summary of a review by the European Science Foundation and the National Academies of Sciences, Engineering and Medicine

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).