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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.

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.

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.

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.

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.

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

[abridged] In the typical giant-impact scenario for the Moon formation most of the Moon's material originates from the impactor. Any Earth-impactor composition difference should, therefore, correspond to a comparable Earth-Moon composition difference. Analysis of Moon rocks shows a close Earth-Moon composition similarity, posing a challenge for the giant-impact scenario, given that impactors were thought to significantly differ in composition from the planets they impact. Here we use a large set of 140 simulations to show that the composition of impactors could be very similar to that of the planets they impact; in $4.9\%$-$18.2\%$ ($1.9\%$-$6.7\%$) of the cases the resulting composition of the Moon is consistent with the observations of $��^{17}O, 15 pages, 12 figures, resubmitted to MNRAS after referee comments. Abstract abridged for arXiv submission

The nutations of Mars are about to be estimated to a few milliarcseconds accuracy with the radioscience experiments onboard InSight and ExoMars 2022. The contribution to the nutations due to the liquid core and tidal deformations will be detected, allowing to constrain the interior of Mars. To avoid introducing systematic errors in the determination of the core properties, an accurate precession and nutation model for a rigidly behaving Mars is needed. Here, we develop such a model with adequate accuracy based on the Torque approach and compare it to previous models. We include in the model the forcings by the Sun, Phobos, Deimos, and the other planets of the solar system. We also include the geodetic precession and nutations. We use semi-analytical developments for the solar and planetary torques, and analytical solutions for the effect of Phobos and Deimos and for the geodetic precession and nutations. With a truncation criterion of 0.025 milliarcseconds in prograde and/or retrograde amplitude, we identify 43 nutation terms. The uncertainty on our solution mainly derives from the observational uncertainty on the current determination of the precession rate of Mars. Uncertainties related to our modeling choices are negligible in comparison. Given the current determination of the precession rate ( $$7608.3\pm 2.1$$ mas/yr, Konopliv et al. in Icarus 274:253–260, 2016. https://doi.org/10.1016/j.icarus.2016.02.052 ), our model predicts a dynamical flattening $$H_{{D}}=0.00538017\pm 0.00000148$$ and a normalized polar moment of inertia $$C/\mathrm{MR}^2=0.36367\pm 0.00010$$ for Mars.

A description of the origin of dust particles, their dynamics and evolution in the atmosphere of Mars and in the vicinity of its moons, Phobos and Deimos, is presented. Theoretical and numerical models are developed that describe the condensation of a substance (for example, water vapor or carbon dioxide) in the atmosphere of Mars, the charging of condensed particles. The parameters of the condensed particles (sizes, charges, etc.) in the atmosphere of Mars are determined. The analysis of the conditions and possibilities for observations and studies of plasma-dust clouds in the atmosphere of Mars in the future space missions ExoMars 2020, Boomerang, etc. is carried out. Theoretical and numerical models are developed for the self-consistent description of dusty plasmas and electric fields at the surfaces of Phobos and Deimos. Numerical modeling of the plasma-dust system and electric fields is carried out. The distributions of dust particles by heights and sizes, the distributions of electrons and ions by heights and speeds, as well as height-distributions of electric fields are determined. The formation of a dusty plasma halo at Mars orbit in the vicinity of Phobos and Deimos is discussed.

Context.The origin of the Martian moons Phobos and Deimos is still poorly understood, and is the focus of intense debate.Aims.We demonstrate that a stratified internal structure of Phobos is compatible with the observed gravity coefficients.Methods.We fit previously derivedC20andC22Phobos gravity coefficients derived from the combined MEX Doppler-tracking data from the close flybys in +2010 and 2013 with respect to the corresponding coefficients of a core–mantle stratification model of Phobos, with two opposite cases: a core denser than the mantle, and a core lighter than the mantle.Results.Only the case with a core lighter than the mantle fits at the 3σlevel the previously reported observed second degree and order coefficientC20, but a homogeneous Phobos cannot be strictly ruled out at the 3σlevel.Conclusions.This possible loosening of the core density might be the result of a displacement of material toward the surface, may be caused by centrifugal forces acting on a loosely packed rubble-pile structure, and/or by a hot-then-cold in-orbit accretion process. These two hypotheses are by no means exhaustive.

The Mars Express (MEX) mission has been successfully operated around Mars since 2004. Among many results, MEX has provided some of the most accurate astrometric data of the two Mars moons, Phobos and Deimos. In this work we present new ephemerides of Mars' moons benefitting from all previously published astrometric data to the most recent MEX SRC data. All in all, observations from 1877 until 2018 and including spacecraft measurements from Mariner 9 to MEX were included. Assuming a homogeneous interior, we fitted Phobos' forced libration amplitude simultaneously with the Martian tidal k2/Q ratio and the initial state of the moons. Our solution of the physical libration 1.09 +/- 0.01 degrees deviates notably from the homogeneous solution. But considering the very low error bar, this may essentially suggest the necessity to consider higher order harmonics, with an improved rotation model, in the future. While most data could be successfully fitted, we found a disagreement between the Mars Reconnaissance Orbiter and the Mars Express astrometric data at the kilometer level probably associated with a biased phase correction. The present solution precision is expected at the level of a few hundreds of meters for Phobos and several hundreds of meters for Deimos for the coming years. The real accuracy of our new ephemerides will have to be confirmed by confrontation with independent observational means., accepted for publication in Astronomy and Astrophysics

In order to achieve high accuracy of autonomous navigation for Mars probes, an integrated navigation method using X-ray pulsar measurement and optical data of viewing Martian moons is proposed. For single X-ray pulsar measurement on board a Mars probe, navigation accuracy is low due to its poor observability. On the other hand, Phobos and Deimos, two natural moons of Mars, are important optical navigation information sources available for Mars missions. However, the Martian moons ephemeris bias and the differences between barycentre and centre of brightness of Martian moons will result in low navigation accuracy. The method of integrated navigation using X-ray pulsar measurement and optical data of viewing Martian moons can overcome the defect and achieve accurate navigation. Two sequential orbit determination algorithms, Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF), are compared. The simulation results show this method can obtain high autonomous navigation accuracy during the phase of a probe orbiting Mars.

Far more definitive information on composition is required to resolve the question of origin for the Martian moons Phobos and Deimos. Current infrared spectra of the objects are inconclusive due to the lack of strong diagnostic features.Definitive compositional measurements of Phobos could be obtained using in-situ X-ray, gamma-ray, or neutronspectroscopy or collecting and returning samples to Earth for analysis. We have proposed, in lieu of those methods, toderive Phobos and Deimos compositional data from secondary ion mass spectrometry (SIMS) measurements by calibratingthe instrument to elemental abundance measurements made for known samples in the laboratory. We describe thePhobos/Deimos Regolith Ion Sample Mission (PRISM) concept here. PRISM utilizes a high-resolution TOF plasma composition analyzer to make SIMS measurements by observing the sputtered species from various locations of the moons' surfaces. In general, the SIMS technique and ion mass spectrometers complement and expand quadrupole mass spectrometer measurements by collecting ions that have been energized to higher energies, 50-100 eV, and making measurements at very low densities and pressures. Furthermore, because the TOF technique accepts all masses all the time,it obtains continuous measurements and does not require stepping through masses. The instrument would draw less than10 W and weigh less than 5 kg. The spacecraft, nominally a radiation-hardened 12U CubeSat, would use a low-thrust SolarElectric Propulsion system to send it on a two-year journey to Mars, where it would co-orbit with Deimos and then Phobos

We show that a model in which Mars grows near Earth and Venus but is then scattered out of the terrestrial region yields a natural pathway to explain the low masses of the Martian moons Phobos & Deimos. In this scenario, the last giant impact experienced by Mars is followed by an extended period (tens to hundreds of Myr) of close passages by other planetary embryos. These close passages perturb and dynamically heat any system of forming satellites left over by the giant impact and can substantially reduce the mass in the satellite system (sometimes to zero). The close passage of massive perturbing bodies also offers the opportunity to capture small objects by three-body scattering. Both mechanisms lead to low mass moon systems with a substantially collisional history., 16 pages, 10 figures, MNRAS in press

The origin of Phobos and Deimos in a giant impact generated disk is gaining larger attention. Although this scenario has been the subject of many studies, an evaluation of the chemical composition of the Mars' moons in this framework is missing. The chemical composition of Phobos and Deimos is unconstrained. The large uncertainty about the origin of the mid-infrared features, the lack of absorption bands in the visible and near-infrared spectra, and the effects of secondary processes on the moons' surface make the determination of their composition very difficult from remote sensing data. Simulations suggest a formation of a disk made of gas and melt with their composition linked to the nature of the impactor and Mars. Using thermodynamic equilibrium we investigate the composition of dust (condensates from gas) and solids (from a cooling melt) that result from different types of Mars impactors (Mars-, CI-, CV-, EH-, comet-like). Our calculations show a wide range of possible chemical compositions and noticeable differences between dust and solids depending on the considered impactors. Assuming Phobos and Deimos as result of the accretion and mixing of dust and solids, we find that the derived assemblage (dust rich in metallic-iron, sulphides and/or carbon, and quenched solids rich in silicates) can be compatible with the observations. The JAXA's MMX (Martian Moons eXploration) mission will investigate the physical and chemical properties of the Maroons, especially sampling from Phobos, before returning to Earth. Our results could be then used to disentangle the origin and chemical composition of the pristine body that hit Mars and suggest guidelines for helping in the analysis of the returned samples., Accepted for publication in ApJ (13/12/2017)

We developed advances laser retroreflectors for solar system exploration, geodesy and for precision test of General Relativity (GR) and new gravitational physics: a micro-reflector array (INRRI, Instrument for landing-Roving laser Retroreflectors Investigations), a midsize reflector array for the European Earth Observation (EO) program, Copernicus (CORA, COpernicus laser Retroreflector Array), a large, single-retroreflector (MoonLIGHT, Moon Laser Instrumentation for General relativity High accuracy Tests). These laser retroreflectors will be fully characterized at the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry Cube/microsat Characterization Facilities Laboratory), a unique and dedicated infrastructure of INFN-LNF (www.lnf.infn.it/esperimenti/etrusco/). Our research program foresees several activities: 1) Developing and characterizing the mentioned laser retroreflector devices to determine landing accuracy, rover positioning during exploration and planetary/Moon’s surface georeferencing. These devices will be passive, laser wavelength- independent, long-lived reference point. INRRI will enable the performance of full-column measurement of trace species in the Mars atmosphere by future space-borne lidars. These measurements will be complementary to highly localized measurements made by gas sampling techniques on the Rover or by laser back-scattering lidar techniques on future orbiters and/or from the surface. INRRI will also support laser and quantum communications, carried out among future Mars Orbiters and Mars Rovers. This will be possible also because the INRRI laser retroreflectors will be metal back-coated and, therefore, will not change the photon polarization. The added value of INRRI is its low mass, compact size, zero maintenance and its usefulness for any future laser altimetry, ranging, communications, atmospheric lidar capable Mars orbiter, for virtually decades after the end of the Mars surface mission, like the Apollo and Lunokhod lunar laser retroreflectors. MoonLIGHT and INRRI are proposed for landings on the Moon (two Google Lunar X Prize Missions, namely Moon Express; Russia’s Luna-27 mission, as well as others under consideration/negotia- tion, also with the help of ASI, ESA and other partnerships); 2) Precision tests of GR with LLR to MoonLIGHT reflectors. Development of new fundamental gravity physics models and study of experimental constraints to these models use also laser ranging and laser reflectors throughout the solar system: extension of general relativity to include Spacetime Torsion, Non-Minimal Coupling between matter and curvature (so-called “ ” theories, or NMC gravity); 3) Extension of program to: Mars, Phobos and Deimos, Jupiter and Saturn icy/rocky moons, Near Earth Asteroids.

Phobos and Deimos are the two small Martian moons, orbiting almost on the equatorial plane of Mars. Recent works have shown that they can accrete within an impact-generated inner dense and outer light disk, and that the same impact potentially forms the Borealis basin, a large northern hemisphere basin on the current Mars. However, there is no a priori reason for the impact to take place close to the north pole (Borealis present location) nor to generate a debris disk in the equatorial plane of Mars (in which Phobos and Deimos orbit). In this paper, we investigate these remaining issues on the giant impact origin of the Martian moons. First, we show that the mass deficit created by the Borealis impact basin induces a global reorientation of the planet to realign its main moment of inertia with the rotation pole (True Polar Wander). This moves the location of the Borealis basin toward its current location. Next, using analytical arguments, we investigate the detailed dynamical evolution of the eccentric inclined disk from the equatorial plane of Mars that is formed by the Martian-moon-forming impact. We find that, as a result of precession of disk particles due to the Martian dynamical flattening $J_{2}$ term of its gravity field and particle-particle inelastic collisions, eccentricity and inclination are damped and an inner dense and outer light equatorial circular disk is eventually formed. Our results strengthen the giant impact origin of Phobos and Deimos that can finally be tested by a future sample return mission such as JAXA's Martian Moons eXploration (MMX) mission., 13 pages, 5 figures. Accepted for publication in ApJ

The paper provides the current understanding of the dust particle dynamics near the surface and in the circummatrian space of the Martian moons based on existing models developed for airless and non-magnetized bodies. In particular we discuss the response of the regolith of the Martian moons to exposure to radiation, the dynamics of charged dust on their surfaces, their plasma environments, the models and indirect observations of their putative dust tori. It is concluded that there is a good theoretical understanding of the behavior of the dynamics of dust particles near the moons Phobos and Deimos. Current models predict dust rings near orbits of the Martian moons based on detailed estimates for the sources and sinks of the dust particles as well as their lifetimes. However, there is no compelling observational evidence for the predicted dust torus around Phobos or Deimos orbits, and there are no observations yet of dust dynamics near their surfaces. Naturally, in order to detect the motion of dust near the surfaces of these moons, and their dust tori we need measurements using a complementary set of sensitive instruments, including impart dust detectors, electric field sensors, and optical cameras in future missions to Mars and its moons.

CHOMIK is the name of a penetrator constructed for sampling and retrieval of Phobos surface material. It formed an integral part of the Phobos Sample Return Mission. In this paper we present its construction and intended mode of operation, since the concept is still viable for future missions either to Phobos or to other small bodies of similar dimensions. We take Phobos as an example to describe the science case for such an instrument and how it might be utilized to resolve important open issues regarding the origin of the Martian moons. Concerning the latter, we place emphasis on measurement techniques and analysis tools for mapping trace element concentrations in returned sample.

Absorption features on Phobos and Deimos in the visible/near infrared wavelength region (0.4–3.9 μm) are mapped using observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Fe 2+ electronic absorptions diagnostic of olivine and pyroxene are not detected. A broad absorption centered around 0.65 μm within the red spectral units of both moons is detected, and this feature is also evident in telescopic, Pathfinder, and Phobos-2 observations of Phobos. A 2.8 μm metal–OH combination absorption on both moons is also detected in the CRISM data, and this absorption is shallower in the Phobos blue unit than in the Phobos red unit and Deimos. The strength, position, and shape of both of the 0.65 μm and 2.8 μm absorptions are similar to features seen on red-sloped, low-albedo primitive asteroids. Two end-member hypotheses are presented to explain the spectral features on Phobos and Deimos. The first invokes the presence of highly desiccated Fe-phyllosilicate minerals indigenous to the bodies, and the second invokes Rayleigh scattering and absorption of small iron particles formed by exogenic space weathering processing, coupled with implantation of H from solar wind. Both end-member hypotheses may play a role, and in situ exploration will be needed to ultimately determine the underlying causes for the pair of spectral features observed on Phobos and Deimos.

Phobos and Deimos are the two small moons of Mars. Recent works have shown that they can accrete within an impact-generated disk. However, the detailed structure and initial thermodynamic properties of the disk are poorly understood. In this paper, we perform high-resolution SPH simulations of the Martian moon-forming giant impact that can also form the Borealis basin. This giant impact heats up the disk material (around $\sim 2000$ K in temperature) with an entropy increase of $\sim 1500$ J K$^{-1}$ kg$^{-1}$. Thus, the disk material should be mostly molten, though a tiny fraction of disk material ($< 5\%$) would even experience vaporization. Typically, a piece of molten disk material is estimated to be meter sized due to the fragmentation regulated by their shear velocity and surface tension during the impact process. The disk materials initially have highly eccentric orbits ($e \sim 0.6-0.9$) and successive collisions between meter-sized fragments at high impact velocity ($\sim 3-5$ km s$^{-1}$) can grind them down to $\sim100 \mu$m-sized particles. On the other hand, a tiny amount of vaporized disk material condenses into $\sim 0.1 \mu$m-sized grains. Thus, the building blocks of the Martian moons are expected to be a mixture of these different sized particles from meter-sized down to $\sim 100 \mu$m-sized particles and $\sim 0.1 \mu$m-sized grains. Our simulations also suggest that the building blocks of Phobos and Deimos contain both impactor and Martian materials (at least 35%), most of which come from the Martian mantle (50-150 km in depth; at least 50%). Our results will give useful information for planning a future sample return mission to Martian moons, such as JAXA's MMX (Martian Moons eXploration) mission., Comment: 11 pages, 6 figures. Accepted for publication in ApJ

Aims. We aim to explore the behavior of the opposition effect as an important tool in optical remote sensing on the nucleus of comet 67P/Churyumov-Gerasimenko (67P), using Rosetta-OSIRIS images acquired in different filters during the approach phase, July-August 2014 and the close flyby images on 14 of February 2015, which contain the spacecraft shadow. Methods. We based our investigation on the global and local brightness from the surface of 67P with respect to the phase angle, also known as phase curve. The local phase curve corresponds to a region that is located at the Imhotep-Ash boundary of 67P. Assuming that the region at the Imhotep-Ash boundary and the entire nucleus have similar albedo, we combined the global and local phase curves to study the opposition-surge morphology and constrain the structure and properties of 67P. The model parameters were furthermore compared with other bodies in the solar system and existing laboratory study. Results. We found that the morphological parameters of the opposition surge decrease monotonically with wavelength, whereas in the case of coherent backscattering this behavior should be the reverse. The results from comparative analysis place 67P in the same category as the two Mars satellites, Phobos and Deimos, which are notably different from all airless bodies in the solar system. The similarity between the surface phase function of 67P and a carbon soot sample at extremely small angles is identified, introducing regolith at the boundary of the Imhotep-Ash region of 67P as a very dark and fluffy layer.© ESO, 2017., The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged

International audience; The origin of Phobos and Deimos is still an open question. Currently, none of the three proposed scenarios for their origin (intact capture of two distinct outer solar system small bodies, co-accretion with Mars, and accretion within an impact-generated disk) are. able to reconcile their orbital and physical properties. Here. we investigate the expected mineralogical composition and size of the grains from which the moons once accreted assuming they formed within an impact-generated accretion disk. A comparison of our results with the present-day spectral properties of the moons allows us to conclude that their building blocks cannot originate from a magma phase, thus preventing their formation in the innermost part of the disk. Instead, gas-to-solid condensation of the building blocks in the outer part of an extended gaseous disk is found as a possible formation mechanism as it does allow reproducing both the spectral and physical properties of the moons. Such a scenario may finally reconcile their orbital and physical properties, alleviating the need to invoke an unlikely capture scenario to explain their physical properties.

One of the paramount stepping stones towards NASA׳s long-term goal of undertaking human missions to Mars is the exploration of the Martian moons. Since a precursor mission to Phobos would be easier than landing on Mars itself, NASA is targeting this moon for future exploration, and ESA has also announced Phootprint as a candidate Phobos sample-and-return mission. Orbital dynamics around small planetary satellites are particularly complex because many strong perturbations are involved, and the classical circular restricted three-body problem (R3BP) does not provide an accurate approximation to describe the system׳s dynamics. Phobos is a special case, since the combination of a small mass-ratio and length-scale means that the sphere-of-influence of the moon moves very close to its surface. Thus, an accurate nonlinear model of a spacecraft׳s motion in the vicinity of this moon must consider the additional perturbations due to the orbital eccentricity and the complete gravity field of Phobos, which is far from a spherical-shaped body, and it is incorporated into an elliptic R3BP using the gravity harmonics series-expansion (ER3BP-GH). In this paper, a showcase of various classes of non-keplerian orbits is identified and a number of potential mission applications in the Mars–Phobos system are proposed: these results could be exploited in upcoming unmanned missions targeting the exploration of this Martian moon. These applications include: low-thrust hovering and orbits around Phobos for close-range observations; the dynamical substitutes of periodic and quasi-periodic Libration Point Orbits in the ER3BP-GH to enable unique low-cost operations for space missions in the proximity of Phobos; their manifold structure for high-performance landing/take-off maneuvers to and from Phobos’ surface and for transfers from and to Martian orbits; Quasi-Satellite Orbits for long-period station-keeping and maintenance. In particular, these orbits could exploit Phobos’ occulting bulk and shadowing wake as a passive radiation shield during future manned flights to Mars to reduce human exposure to radiation, and the latter orbits can be used as an orbital garage, requiring no orbital maintenance, where a spacecraft could make planned pit-stops during a round-trip mission to Mars.

We reconsider two scenarios for the formation of Phobos and Deimos from a circum-martian accretion disk of debris: the strong tide regime for which accretion occurs close to the planet at the Roche limit and the weak tide regime for which accretion occurs farther from the planet. We assume a disk with an initial mass of 10 18 kg (Craddock, R.A. [2011]. Icarus 211, 1150–1161). In the strong tide regime, the disk loses its material by viscous spreading inward to and outward from the planet. When outward moving material crosses the Roche limit, small-sized moonlets are accreted from gravitational instabilities with a shape and density similar to Phobos and Deimos. Due to the gravitational torque exerted by the disk, the moonlets migrate away from the planet, though they cannot reach the synchronous orbit (lying at 6 Mars’ radii). After the disk has lost most of its mass they rapidly fall back onto Mars due to the tidal decay of their orbits. Although, the total mass of moonlets is comparable to the mass of Phobos, their survival time does not exceed 200 Ma, which is incompatible with the formation of Phobos and Deimos early in Mars’ history. In the weak tide regime, moonlets can accrete near the synchronous orbit with the mass of Deimos in a disk of up to 10 18 kg (similarly to planetary embryos formation in the protoplanetary disk). A Phobos-mass embryo can also be formed in the same disk but closer to Mars (at 3–4 Mars’ radii) so that it rapidly falls back onto Mars by tidal decay of its orbit. However, several embryos may accrete together in the disk (similarly to the final stage of terrestrial planet formation), and Phobos and Deimos may be the last two remnants of those bodies formed near the synchronous distance to Mars. Further investigations are still needed to understand such accretion mechanism within a circum-martian disk primarily extending below the synchronous orbit.

GETEMME (Gravity, Einstein’s Theory, and Exploration of the Martian Moons’ Environment), a mission which is being proposed in ESA’s Cosmic Vision program, shall be launched for Mars on a Soyuz Fregat in 2020. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive Laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine Laser range measurements to the reflectors on Phobos and Deimos. Also, asynchronous two-way Laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellite system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter β as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame.

Despite many efforts an adequate theory describing the origin of Phobos and Deimos has not been realized. In recent years a number of separate observations suggest the possibility that the martian satellites may have been the result of giant impact. Similar to the Earth–Moon system, Mars has too much angular momentum. A planetesimal with 0.02 Mars masses must have collided with that planet early in its history in order for Mars to spin at its current rate (Dones, L., Tremaine, S. [1993]. Science 259, 350–354). Although subject to considerable error, current crater-scaling laws and an analysis of the largest known impact basins on the martian surface suggest that this planetesimal could have formed either the proposed 10,600 by 8500-km-diameter Borealis basin, the 4970-km-diameter Elysium basin, the 4500km-diameter Daedalia basin or, alternatively, some other basin that is no longer identifiable. It is also probable that this object impacted Mars at a velocity great enough to vaporize rock (>7 km/s), which is necessary to place large amounts of material into orbit. If material vaporized from the collision with the Mars-spinning planetesimal were placed into orbit, an accretion disk would have resulted. It is possible that as material condensed and dissipated beyond the Roche limit forming small, low-mass satellites due to gravity instabilities within the disk. Once the accretion disk dissipated, tidal forces and libration would have pulled these satellites back down toward the martian surface. In this scenario, Phobos and Deimos would have been among the first two satellites to form, and Deimos the only satellite formed—and preserved—beyond synchronous rotation. The low mass of Phobos and Deimos is explained by the possibility that they are composed of loosely aggregated material from the accretion disk, which also implies that they do not contain any volatile elements. Their orbital eccentricity and inclination, which are the most difficult parameters to explain easily with the various capture scenarios, are the natural result of accretion from a circum-planetary disk.

Dusty plasmas are shown to be formed in a surface layer over the illuminated part of Martian satellites Phobos and Deimos owing to photoelectric and electrostatic processes. The distribution functions of photoelectrons near surfaces of the satellites, altitude dependences of the density of dust particles, and their charges and sizes, as well as electric fields, have been determined within a physical-mathematical model for the self-consistent description of densities of photoelectrons and dust particles over the surface of the illuminated parts of Phobos and Deimos. In view of a weak gravitational field, dust particles rising over the surfaces of Phobos and Deimos are larger than those over the surface of the Moon. In this case, the role of adhesion, which is a significant process preventing the separation of dust particles from the lunar surface, is much smaller on Phobos and Deimos.

This review provides explanations of how geodesy, rotation and gravity can be addressed using radioscience data of an orbiter around a planet or of the lander on its surface. The planet Mars is the center of the discussion. The information one can get from orbitography and radioscience in general concerns the global static gravitational field, the time variation of the gravitational field induced by mass exchange between the atmosphere and the ice caps, the time variation of the gravitational field induced by the tides, the secular changes in the spacecraft's orbit induced by the little moons of Mars named Phobos and Deimos, the gravity induced by particular targets, the Martian ephemerides, and Mars' rotation and orientation. The paper addresses as well the determination of the geophysical parameters of Mars and, in particular, the state of Mars' core and its size, which is important for understanding the planet's evolution. Indeed, the state and dimension of the core determined from the moment of inertia and nutation depend in turn on the percentage of light elements in the core as well as on the core temperature, which is related to heat transport in the mantle. For example, the radius of the core has implications for possible mantle convection scenarios and, in particular, for the presence of a perovskite phase transition at the bottom of the mantle. This is also important for our understanding of the large volcanic province Tharsis on the surface of Mars.

Recent works have shown that Martian moons Phobos and Deimos may have accreted within a giant impact-generated disk whose composition is about an equal mixture of Martian material and impactor material. Just after the giant impact, the Martian surface is heated up to $\sim3000-6000$ K and the building blocks of moons, including volatile-rich vapor, are heated up to $\sim2000$ K. In this paper, we investigate the volatile loss from the building blocks of Phobos and Deimos by hydrodynamic escape of vapor and radiation pressure on condensed particles. We show that a non-negligible amount of volatiles ($> 10\%$ of the vapor with temperature $> 1000$ K via hydrodynamic escape, and moderately volatile dusts that condense at $\sim700-2000$ K via radiation pressure) could be removed just after the impact during their first signle orbit from their pericenters to apocenters. Our results indicate that bulk Phobos and Deimos are depleted in volatile elements. Together with future explorations such as JAXA's MMX (Martian Moons eXploration) mission, our results would be used to constrain the origin of Phobos and Deimos., 15 pages, 8 figures. Accepted for publication in ApJ

Context. Both Martian moons, Phobos and Deimos, have been observed during several imaging campaigns by the Super Resolution Channel (SRC) on the Mars Express probe. Several tens of images are obtained during mutual event observations – when the Martian moons are both observed or together with another solar system body. These observations provide new opportunities to determine the bodies’ positions in their orbits. Aims. A method was sought to automate the observation of the positions of the imaged bodies. Within one image sequence a similarly accurate localization of the objects in all images should be possible. Methods. Shape models of Phobos and Deimos are applied to simulate the appearance of the bodies in the images. Matching the illuminated simulation against the observation provides a reliable determination of the bodies’ location within the image. To enhance the matching confidence several corrections need to be applied to the simulation to closely reconstruct the observation. Results. A list of 884 relative positions between the different objects is provided through the Centre de Données astronomiques de Strasbourg (CDS).

Observations and meteorites indicate that the Martian materials are enigmatically distributed within the inner solar system. A mega impact on Mars creating a Martian hemispheric dichotomy and the Martian moons can potentially eject Martian materials. A recent work has shown that the mega-impact-induced debris is potentially captured as the Martian Trojans and implanted in the asteroid belt. However, the amount, distribution, and composition of the debris has not been studied. Here, using hydrodynamic simulations, we report that a large amount of debris ($\sim 1\%$ of Mars' mass), including Martian crust/mantle and the impactor's materials ($\sim 20:80$), are ejected by a dichotomy-forming impact, and distributed between $\sim 0.5-3.0$ astronomical units. Our result indicates that unmelted Martian mantle debris ($\sim 0.02\%$ of Mars' mass) can be the source of Martian Trojans, olivine-rich asteroids in the Hungarian region and the main asteroid belt, and some of which even hit early Earth. A mega impact can naturally implant Martian mantle materials within the inner solar system., 8 pages, 5 figures. Accepted for publication in ApJL

More than 490 elliptical aerobraking and science phasing orbits made by Mars Global Surveyor (MGS) in 1997 and 1998 provide unprecedented coverage of the solar wind in the vicinity of the orbits of the martian moons Phobos and Deimos. We have performed a comprehensive survey of magnetic field perturbations in the solar wind to search for possible signatures of solar wind interaction with dust or gas escaping from the moons. A total of 1246 solar wind disturbance events were identified and their distribution was examined relative to Phobos, the Phobos orbit, and the Deimos orbit. We find that the spatial distribution of solar wind perturbations does not increase near or downstream of Phobos, Phobos’ orbit, or Deimos’ orbit, which would have been expected if there is significant outgassing or dust escape from the martian moons. Of the 1246 magnetic field perturbation events found in the MGS data set, 11 events were found within 2000 km of the Phobos orbit, while three events were found within 2000 km of the Deimos orbit. These events were analyzed in detail and found to likely have other causes than outgassing/dust escape from the martian moons. Thus we conclude that the amount of gas/dust escaping the martian moons is not significant enough to induce detectable magnetic field perturbations in the solar wind. In essence we have not found any clear evidence in the MGS magnetic field data for outgassing or dust escape from the martian moons.

The Phobos-Soil project, based on a new generation of spacecraft, is aimed at the study of Phobos, one of the Martian moons. The main goal of the project is to bring soil samples from the surface of Phobos to the Earth for a scrutinized analysis of the relic matter collected on one of the Solar System’s minor bodies. The project is considered to be a step in the long-scale extensive quest for data on planets, comets, asteroids, and solving a vast number of other theoretical and applied problems.

This paper reports on an update to the orbits and masses of the Martian satellites Phobos and Deimos. We obtained the orbits by fitting a numerical integration to all available Earth-based astrometry through the opposition of 2003, spacecraft imaging observations through 2007, and the Doppler tracking of the Viking and Phobos 2 spacecraft; the Doppler data provide information on the satellite masses. Our dynamical model included the figure acceleration due to a librating Phobos; we determined the amplitude of the forced libration. We also took into account the secular acceleration of Phobos due to the tide that it raises on Mars and estimated the Martian tidal quality factor Q. We provide an assessment of the accuracy of the orbits and a geometrical description of the orbits in the form of mean elements.

Many new small moons of the giant planets have been discovered recently. In parallel, satellites of several asteroids, e.g., Ida, have been found. Strikingly, a majority of these new-found planetary moons are estimated to have very low densities, which, along with their hypothesized accretionary origins, suggests a rubble internal structure. This, coupled to the fact that many asteroids are also thought to be particle aggregates held together principally by self-gravity, motivates the present investigation into the possible ellipsoidal shapes that a rubble-pile satellite may achieve as it orbits an aspherical primary. Conversely, knowledge of the shape will constrain the granular aggregate's orbit—the closer it gets to a primary, both primary's tidal effect and the satellite's spin are greater. We will assume that the primary body is sufficiently massive so as not to be influenced by the satellite. However, we will incorporate the primary's possible ellipsoidal shape, e.g., flattening at its poles in the case of a planet, and the proloidal shape of asteroids. In this, the present investigation is an extension of the first classical Darwin problem to granular aggregates. General equations defining an ellipsoidal rubble pile's equilibrium about an ellipsoidal primary are developed. They are then utilized to scrutinize the possible granular nature of small inner moons of the giant planets. It is found that most satellites satisfy constraints necessary to exist as equilibrated granular aggregates. Objects like Naiad, Metis and Adrastea appear to violate these limits, but in doing so, provide clues to their internal density and/or structure. We also recover the Roche limit for a granular satellite of a spherical primary, and employ it to study the martian satellites, Phobos and Deimos, as well as to make contact with earlier work of Davidsson [Davidsson, B., 2001. Icarus 149, 375–383]. The satellite's interior will be modeled as a rigid-plastic, cohesion-less material with a Drucker–Prager yield criterion. This rheology is a reasonable first model for rubble piles. We will employ an approximate volume-averaging procedure that is based on the classical method of moments, and is an extension of the virial method [Chandrasekhar, S., 1969. Ellipsoidal Figures of Equilibrium. Yale Univ. Press, New Haven] to granular solid bodies.

The Moon and the moons of Mars should be extremely quiet seismically and could therefore become sensitive gravitational wave detectors, if instrumented properly. Highly sensitive displacement sensors could be deployed on these planetary bodies to monitor the motion induced by gravitational waves. A superconducting displacement sensor with a 10-kg test mass cooled to 2 K will have an intrinsic instrument noise of 10 −16 m Hz −1/2 . These sensors could be tuned to the lowest two quadrupole modes of the body or operated as a wideband detector below its fundamental mode. An interesting frequency range is 0.1–1 Hz, which will be missed by both the ground detectors on the Earth and LISA and would be the best window for searching for stochastic background gravitational waves. Phobos and Deimos have their lowest quadrupole modes at 0.2–0.3 Hz and could offer a sensitivity h min ⩽ 10 −22 Hz −1/2 within their resonance peaks, which is within two orders of magnitude from the goal of the Big Bang Observer (BBO). The lunar and Martian moon detectors would detect many interesting foreground sources in a new frequency window and could serve as a valuable precursor for BBO.

Aims. This paper give positions of Martian satellites system from CCD observations obtained at the Cassegrain focus of a 1.6 m reflector for the years 1995 and 2003. Methods. These positions were reduced using the scale and orientation parameters, determined from star field positions of Uranus and Pluto systems’ observations that were made in the same night as Mars observations. Results. They are compared with the theoretically calculated positions from JPL Development planetary Ephemeris – DE405. The standard deviations of the residuals, observed minus calculated positions, right ascension and declination of Phobos and Deimos, respectively are σ = 0. �� 079 and σ = 0. 072.

International audience; The determination of the ephemeris of the Martian moons has benefited from observations of their plane-of-sky positions derived from images taken by cameras onboard spacecraft orbiting Mars. Images obtained by the Super Resolution Camera (SRC) onboard Mars Express (MEX) have been used to derive moon positions relative to Mars on the basis of a fit of a complete dynamical model of their motion around Mars. Since, these positions are computed from the relative position of the spacecraft when the images are taken, those positions need to be known as accurately as possible. An accurate MEX orbit is obtained by fitting two years of tracking data of the Mars Express Radio Science (MaRS) experiment onboard MEX. The average accuracy of the orbits has been estimated to be around 20-25 m. From these orbits, we have re-derived the positions of Phobos and Deimos at the epoch of the SRC observations and compared them with the positions derived by using the MEX orbits provided by the ESOC navigation team. After fit of the orbital model of Phobos and Deimos, the gain in precision in the Phobos position is roughly 30 m, corresponding to the estimated gain of accuracy of the MEX orbits. A new solution of the GM of the Martian moons has also been obtained from the accurate MEX orbits, which is consistent with previous solutions and, for Phobos, is more precise than the solution from the Mars Global Surveyor (MGS) and Mars Odyssey (ODY) tracking data. It will be further improved with data from MEX-Phobos closer encounters (at a distance less than 300 km). This study also demonstrates the advantage of combining observations of the moon positions from a spacecraft and from the Earth to assess the real accuracy of the spacecraft orbit. In turn, the natural satellite ephemerides can be improved and participate to a better knowledge of the origin and evolution of the Martian moons.

Celestial mechanical integrations for the whole solar system are carried out over four billion years before and after the present. The orbital solution of the solar system is stable during this whole time period. An instantaneous spin axis model including triaxiality is developed. In particular, spin axis precession, the Martian obliquity, solar torques, and the orbital eccentricity/inclination of Mars are studied. Model dependences from general relativity, solar oblateness, the Martian moons, solar mass loss, etc. are tested. Although the obliquity of Mars sometimes shows dramatic variations, some structures are robust and seem insensitive to the initial spin precession rate. A full integration is carried out during a total of 8000 Myr resulting in a Martian obliquity that is restricted between 10 and 60°. The problems with numerical noise due to limited machine precision, integration step sizes, and the chaotic sensitivity of the solutions are studied and discussed. The limited machine precision (15-16 figures) alone is found to limit the duration of exact obliquity solutions to about 80 Myr.

International audience; We present new ephemerides of Phobos and Deimos that are fit to observations from 1877 to 2005 and include recent spacecraft observations by Mars Global Surveyor and Mars Express. In contrast to earlier models, this is the first completely numerical one. In particular, the tidal effects have been modeled by the tidal bulge raised by each moon on the planet, instead of fitting secular accelerations in the satellite longitudes. This partly avoids absorbing the Deimos observational errors in its related tidal acceleration. Moreover, applying this model to other systems will be easier. Our estimate of the Martian dissipation is Q = 79.91±0.69 (1sigma-formal error) when assuming k2 = 0.152 for the Martian Love number and G{m}_Ph = 0.68×106 m^3/s2 for the Phobos mass. We also report the possibility of fitting the Phobos oblateness gravity field. We suspect a non-uniform density for Phobos or a bias in either the observations or the Martian gravity field. A FORTRAN subroutine that computes the Martian moons' ephemerides is available on request.

The electric solar wind sail (E-sail) propellantless propulsion device uses long, charged metallic tethers to tap momentum from the solar wind to produce spacecraft propulsion. If flying through planetary or moon eclipse, the long E-sail tethers can undergo significant thermal contraction and expansion. Rapid shortening of the tether increases its tension due to inertia of the tether and a Remote Unit that is located on the tether tip (a Remote Unit is part of typical E-sail designs). We analyse by numerical simulation the conditions under which eclipse induced stresses are safe for E-sail tethers. We calculate the closest safe approach distances for Earth, Moon, Venus, Mars, Jupiter, Ceres and an exemplary 300 km main belt asteroid Interamnia for circular, parabolic and hyperbolic orbits. We find that any kind of eclipsing is safe beyond approximately 2.5 au distance, but for terrestrial planets safety depends on the parameters of the orbit. For example, for Mars the safe distance with 20 km E-sail tether lies between Phobos and Deimos orbits., 12 pages, 4 figures, 2 tables, accepted in Acta Astronautica

It has long been suspected that Mars might be encircled by two faint rings, one originating from each of its moons Phobos and Deimos. Meteoroid impacts into these moons should release clouds of dust that quickly spread out to become rings; similar dust rings have been associated with several small inner moons of the gas giants. On May 28, 2001 Mars’ hypothetical ring plane appeared edge-on to Earth within weeks of its opposition, providing the best Earth-based opportunity to detect these rings in several decades. Using the Wide Field/Planetary Camera 2 (WFPC2) on the Hubble Space Telescope, we obtained a set of deep exposures off the east and west limbs of Mars to search for these hypothetical rings. No rings were detected. This result limits normal optical depths to ∼3×10−8 for the Phobos ring and ∼10−7 for the Deimos ring. These limits fall at the low end of prior dynamical predictions and a factor of 1000 below previous observational limits. However, our limit for the Deimos ring is more tentative because of large uncertainties about this ring's expected shape, size and orientation. Our data set is also sensitive to small, previously undetected inner moons. No moons were detected down to a radius limit of 75–125 m. Longitudinal coverage of the region near and between Phobos and Deimos is 40–80% complete. We conclude by describing a promising opportunity for further Martian ring viewing in December 2007.

With the collection of six years of MGS tracking data and three years of Mars Odyssey tracking data, there has been a continual improvement in the JPL Mars gravity field determination. This includes the measurement of the seasonal changes in the gravity coefficients (e.g., J ¯ 2 , J ¯ 3 , C ¯ 21 , S ¯ 21 , C ¯ 31 , S ¯ 31 ) caused by the mass exchange between the polar ice caps and atmosphere. This paper describes the latest gravity field MGS95J to degree and order 95. The improvement comes from additional tracking data and the adoption of a more complete Mars orientation model with nutation, instead of the IAU 2000 model. Free wobble of the Mars' spin axis, i.e. polar motion, has been constrained to be less than 10 mas by looking at the temporal history of C ¯ 21 and S ¯ 21 . A strong annual signature is observed in C ¯ 21 , and this is a mixture of polar motion and ice mass redistribution. The Love number solution with a subset of Odyssey tracking data is consistent with the previous liquid outer core determination from MGS tracking data [Yoder et al., 2003. Science 300, 299–303], giving a combined solution of k 2 = 0.152 ± 0.009 using MGS and Odyssey tracking data. The solutions for the masses of the Mars' moons show consistency between MGS, Odyssey, and Viking data sets; Phobos GM = ( 7.16 ± 0.005 ) × 10 −4 km 3 / s 2 and Deimos GM = ( 0.98 ± 0.07 ) × 10 −4 km 3 / s 2 . Average MGS orbit errors, determined from differences in the overlaps of orbit solutions, have been reduced to 10-cm in the radial direction and 1.5 m along the spacecraft velocity and normal to the orbit plane. Hence, the ranging to the MGS and Odyssey spacecraft has resulted in position measurements of the Mars system center-of-mass relative to the Earth to an accuracy of one meter, greatly reducing the Mars ephemeris errors by several orders of magnitude, and providing mass estimates for Asteroids 1 Ceres, 2 Pallas, 3 Juno, 4 Vesta, and 324 Bamberga.

Observations of Phobos and Deimos, carried out by the SRC (Super Resolution Channel) on the Mars Express spacecraft between May 2004-April 2005, were used to determine the center-of-figure positions of the two Satellites with accuracies of 0.5-5 km (Phobos) and 1.0 km (Deimos). We find that the Phobos and Deimos orbit predictions from NASA-JPL (Jet Propulsion Laboratory) and ESA-ESOC (European Space Operation Center) differ substantially among each other and also do not agree with the actually observed positions of the satellites. Hence, our new astrometric data may motivate new efforts for Phobos and Deimos orbit modeling.

A high priority mission currently being formulated by NASA is to capture all or part of an asteroid and return it to cis-lunar space for examination by an astronaut crew. Two major mission architectures are currently being considered: in the first (Mission Concept A), a spacecraft would rendezvous and capture an entire free flying asteroid (up to 14 meters in diameter), and in the second (Mission Concept B), a spacecraft would rendezvous with a large asteroid (which could include one of the Martian moons) and retrieve a boulder (up to 4 meters in diameter). A critical element of the mission is the system that will capture the asteroid or boulder material, enclose it and secure it for the return flight. This paper describes the design concepts, concept of operations, structural sizing and masses of capture systems that are based on a new and novel Tendon-Actuated Lightweight In-Space MANipulator (TALISMAN) general-purpose robotic system. Features of the TALISMAN system are described and the status of its technology development is summarized. TALISMAN-based asteroid material retrieval system concepts and concepts-of-operations are defined for each asteroid mission architecture. The TALISMAN-based capture systems are shown to dramatically increase operational versatility while reducing mission risk. Total masses of TALISMAN-based systems are presented, reinforcing the mission viability of using a manipulator-based approach for the asteroid redirect mission.

The Mars Dust Counter (MDC) is an impact-ionization dust detector on board the Japanese Mars mission NOZOMI, which was launched on 1998-07-04. It is an improved type of MDC-HITEN and MDC-BREMSAT and has three detection channels (electron, iron, and neutral) to discriminate noise signals from impact signals. The main aim of the MDC is to measure dust particles around Mars and reveal the distribution of the predicted Martian ring or torus of dust from Phobos and Deimos. On 1998-07-13, the MDC detected the first impact signal. On 1998-11-18, NOZOMI encountered the Leonids meteoroid stream. The MDC detected two dust impacts, but directional analysis showed that those particles probably did not belong to the Leonids. The NOZOMI orbital plan was changed; Mars insertion was postponed to be on 2004-01-01. By the end of 1999, MDC had detected more than 40 particles, including at least three — maybe five - particles of interstellar origin. Between 1999 and 2003, MDC-NOZOMI can thus continuously measure interplanetary dust.

Celestial mechanical simulations from a purely classical point of view of the whole solar system, including our Moon and the Mars moons { Phobos and Deimos { are carried out for 2 millions of years before present. Within the classical approximation, the results are derived at a very high level of accuracy. Eects from general relativity for a number of variables are investigated and found to be small. For climatic studies of about 1 Myr, general relativity can safely be ignored. Three dierent and independent integrations schemes are used in order to exclude numerical anomalies. The converged results from all methods are found to be in complete agreement. For verication, a number of properties such as spin axis precession, nutation, and orbit inclination for Earth and Mars have been calculated. Times and positions of equinoxes and solstices are continously monitored. As also observed earlier, the obliquity of the Earth is stabilized by the Moon. On the other hand, the obliquity of Mars shows dramatic variations. Climatic influences due to celestial variables for the Earth and Mars are studied. Instead of using mean insolation as in the usual applications of Milankovitch theory, the present approach focuses on the instantaneous solar radiation power (insolation) at each summer solstice. Solar radiation power is compared to the derivative of the icevolume and these quantities are found to be in excellent agreement. Orbital precessions for the inner planets are studied as well. In the case of Mercury, it is investigated in detail.