| 1. |
- Aizawa, S., et al.
(författare)
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Cross-comparison of global simulation models applied to Mercury's dayside magnetosphere
- 2021
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- We present the first comparison of multiple global simulations of the solar wind interaction with Mercury's dayside magnetosphere, conducted in the framework of the international collaborative project SHOTS - Studies on Hermean magnetosphere Oriented Theories and Simulations. Two 3D magnetohydrodynamic and two 3D hybrid simulation codes are used to investigate the global response of the Hermean magnetosphere without its exosphere to a northward-oriented interplanetary magnetic field. We cross-compare the results of the four codes for a theoretical case and a MESSENGER orbit with similar upstream plasma conditions. The models agree on bowshock and magnetopause locations at 2.1 ± 0.11 and 1.4 ± 0.1 Mercury planetary radii, respectively. The latter locations may be influenced by subtle differences in the treatment of the plasma boundary at the planetary surface. The predicted magnetosheath thickness varies less between the codes. Finally, we also sample the plasma data along virtual trajectories of BepiColombo's Magnetospheric and Planetary Orbiter. Our ability to accurately predict the structure of the Hermean magnetosphere aids the analysis of the onboard plasma measurements of past and future magnetospheric missions.
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| 2. |
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| 3. |
- Blanc, Michel, et al.
(författare)
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Joint Europa Mission (JEM) : a multi-scale study of Europa to characterize its habitability and search for extant life
- 2020
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Europa is the closest and probably the most promising target to search for extant life in the Solar System, based on complementary evidence that it may fulfil the key criteria for habitability: the Galileo discovery of a sub-surface ocean; the many indications that the ice shell is active and may be partly permeable to transfer of chemical species, biomolecules and elementary forms of life; the identification of candidate thermal and chemical energy sources necessary to drive a metabolic activity near the ocean floor. In this article we are proposing that ESA collaborates with NASA to design and fly jointly an ambitious and exciting planetary mission, which we call the Joint Europa Mission (JEM), to reach two objectives: perform a full characterization of Europa's habitability with the capabilities of a Europa orbiter, and search for bio-signatures in the environment of Europa (surface, subsurface and exosphere) by the combination of an orbiter and a lander. JEM can build on the advanced understanding of this system which the missions preceding JEM will provide: Juno, JUICE and Europa Clipper, and on the Europa lander concept currently designed by NASA (Maize, report to OPAG, 2019). We propose the following overarching goals for our Joint Europa Mission (JEM): Understand Europa as a complex system responding to Jupiter system forcing, characterize the habitability of its potential biosphere, and search for life at its surface and in its sub-surface and exosphere. We address these goals by a combination of five Priority Scientific Objectives, each with focused measurement objectives providing detailed constraints on the science payloads and on the platforms used by the mission. The JEM observation strategy will combine three types of scientific measurement sequences: measurements on a high-latitude, low-altitude Europan orbit; in-situ measurements to be performed at the surface, using a soft lander; and measurements during the final descent to Europa's surface. The implementation of these three observation sequences will rest on the combination of two science platforms: a soft lander to perform all scientific measurements at the surface and sub-surface at a selected landing site, and an orbiter to perform the orbital survey and descent sequences. We describe a science payload for the lander and orbiter that will meet our science objectives. We propose an innovative distribution of roles for NASA and ESA; while NASA would provide an SLS launcher, the lander stack and most of the mission operations, ESA would provide the carrier-orbiter-relay platform and a stand-alone astrobiology module for the characterization of life at Europa's surface: the Astrobiology We Laboratory (AWL). Following this approach, JEM will be a major exciting joint venture to the outer Solar System of NASA and ESA, working together toward one of the most exciting scientific endeavours of the 21st century: to search for life beyond our own planet.
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| 4. |
- Blöcker, Aljona, et al.
(författare)
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Variability of Io's poynting flux : A parameter study using MHD simulations
- 2020
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- Io's plasma interaction creates an electromagnetic coupling between Io and Jupiter through Alfvén waves triggering the generation of auroral footprints in Jupiter's southern and northern hemispheres. The brightness of Io's footprints undergoes periodic variations that are primarily modulated by Io's local plasma interaction through the Poynting flux radiated away from the moon. The periodic pattern with two maxima near 110∘ and 290∘ Jovian longitude where Io crosses the dense plasma sheet is generally understood. However, some characteristics, like the 2-4 times stronger brightening of the southern footprint near Jovian longitude 110∘ or the lack of response to Io's eclipse passage, are not fully understood. We systematically study variations in Io's plasma interaction and the Poynting flux using a 3D magnetohydrodynamic model, performing a series of simulations with different upstream plasma conditions and models of Io's atmosphere. Our results indicate that the strong Jovian magnetic field near 110∘ plays a more important role than previously estimated for the strong brightening there. We find that the Poynting flux is not fully saturated for a wide range of possible atmospheric densities (6 ×1018 - 6 ×1021 m-2) and that density changes in the atmosphere by a factor of > 3, as possibly happening during Io's eclipse passage, lead to a change of the Poynting flux by > 20%. Assuming that these expected changes in Poynting flux also apply to the footprints, the non-detection of a dimming in the footprint during the eclipse by Juno-UVS suggests that Io's global atmospheric density decreases by a factor of < 2.5. We show that for smaller atmospheric scale heights (i.e. a more confined atmosphere), changes in the atmospheric density have less effect on the Poynting flux. The missing response of the footprint to the eclipse hence might also be consistent with a density decrease by a factor of > 3, if the effective atmospheric scale height is small (< 120 km). Finally, we provide new analytical approximations that can be used for analyzing the effect of the local interaction responsible for the footprint variability in future studies.
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| 5. |
- De Keyser, J., et al.
(författare)
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In situ plasma and neutral gas observation time windows during a comet flyby : Application to the Comet Interceptor mission
- 2024
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- A comet flyby, like the one planned for ESA's Comet Interceptor mission, places stringent requirements on spacecraft resources. To plan the time line of in situ plasma and neutral gas observations during the flyby, the size of the comet magnetosphere and neutral coma must be estimated well. For given solar irradiance and solar wind conditions, comet composition, and neutral gas expansion speed, the size of gas coma and magnetosphere during the flyby can be estimated from the gas production rate and the flyby geometry. Combined with flyby velocity, the time spent in these regions can be inferred and a data acquisition plan can be elaborated for each instrument, compatible with the limited data storage capacity. The sizes of magnetosphere and gas coma are found from a statistical analysis based on the probability distributions of gas production rate, flyby velocity, and solar wind conditions. The size of the magnetosphere as measured by bow shock standoff distance is 105-106 km near 1 au in the unlikely case of a Halley-type target comet, down to a nonexistent bow shock for targets with low activity. This translates into durations up to 103-104 seconds. These estimates can be narrowed down when a target is identified far from the Sun, and even more so as its activity can be predicted more reliably closer to the Sun. Plasma and neutral gas instruments on the Comet Interceptor main spacecraft can monitor the entire flyby by using an adaptive data acquisition strategy in the context of a record-and-playback scenario. For probes released from the main spacecraft, the inter-satellite communication link limits the data return. For a slow flyby of an active comet, the probes may not yet be released during the inbound bow shock crossing.
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| 6. |
- Escamilla-Roa, Elizabeth, et al.
(författare)
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DFT study of electronic and redox properties of TiO2 supported on olivine for modelling regolith on Moon and Mars conditions
- 2020
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide TiO2 is one of the most studied oxides in photocatalysis, due to its electronic structure and its wide variety of applications, such as gas sensors and biomaterials, and especially in methane-reforming catalysis. Titanium dioxide and olivine have been detected both on Mars and our Moon. It has been postulated that on Mars photocatalytic processes may be relevant for atmospheric methane fluctuation, radicals and perchlorate productions etc. However, to date no investigation has been devoted to modelling the properties of TiO2 adsorbed on olivine surface.The goal of this study is to investigate at atomic level with electronic structure calculations based on the Density Functional Theory (DFT), the atomic interactions that take place during the adsorption processes for formation of a TiO regolith. This model is formed with different TiO films adsorbed on olivine (forsterite) surfaces, one of the most common minerals in Universe, Earth, Mars, cometary and interstellar dust. We propose three regolith models to simulate the principal phase of titanium oxide (TiO, Ti2O3 and TiO2). The models show different adsorption processes i.e. physisorption and chemisorption. Our results suggest that the TiO is the most reactive phase and produces a strong exothermic effect. Besides, we have detailed, from a theoretical point of view, the effect that has the adsorption process in the electronic properties such as electronic density of state (DOS) and oxide reduction process (redox). This theoretical study can be important to understand the formation of new materials (supports) that can be used as support in the catalytic processes that occur in the Earth, Mars and Moon. Also, it may be important to interpret the present day photochemistry and interaction of regolith and airborne aerosols in the atmosphere on Mars or to define possible catalytic reactions of the volatiles captured on the Moon regolith.
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| 7. |
- Fleith, Patrick, et al.
(författare)
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In-situ approach for thermal energy storage and thermoelectricity generation on the Moon: Modelling and simulation
- 2020
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- Human, tele-operated rovers, and surface infrastructures are now being actively considered for lunar polar exploration. Current approaches to energy provision consider, among others, hybrid direct energy/chemical technologies, such as solar photovoltaic arrays, batteries, and regenerative fuel cells. Due to the long period of darkness on the Moon and the challenges this poses to the aforementioned conventional energy generation and storage technologies, there is a need to assess the potential of In-Situ Resources Utilization (ISRU) methods to enable or supplement long duration missions. We present a computational model (MATLAB) of a Thermal Energy Storage (TES) system coupled to drive a heat engine (Thermoelectric Generator) to produce electricity. The TES medium designed is based off processed lunar regolith, an abundant material present on the surface of the Moon. The architecture has been optimized to provide a minimum electrical power of 36 W per unit after 66 h of polar night, but the modular nature of the model allows other ranges of parameter to be simulated. A trade-off between this ISRU-based concept and conventional approaches for energy production and storage was performed and ranked TES and thermoelectricity generation as the least appropriate option. This result is valuable in a period of enthusiasm towards ISRU. It shows that processes exploiting extraterrestrial materials instead of Earth supplies are not systematically attractive. Despite the non-favorable performances for the proposed concept, some perspectives for the TES system are given as well as potential model improvements such as the need to assess the use of a Stirling heat engine.
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| 8. |
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| 9. |
- Madanian, H., et al.
(författare)
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Electron dynamics near diamagnetic regions of comet 67P/Churyumov- Gerasimenko
- 2020
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Ingår i: Planetary and Space Science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0032-0633 .- 1873-5088. ; 187
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Tidskriftsartikel (refereegranskat)abstract
- The Rosetta spacecraft detected transient and sporadic diamagnetic regions around comet 67P/Churyumov-Gerasimenko. In this paper we present a statistical analysis of bulk and suprathermal electron dynamics, as well as a case study of suprathermal electron pitch angle distributions (PADs) near a diamagnetic region. Bulk electron densities are correlated with the local neutral density and we find a distinct enhancement in electron densities measured over the southern latitudes of the comet. Flux of suprathermal electrons with energies between tens of eV to a couple of hundred eV decreases each time the spacecraft enters a diamagnetic region. We propose a mechanism in which this reduction can be explained by solar wind electrons that are tied to the magnetic field and after having been transported adiabatically in a decaying magnetic field environment, have limited access to the diamagnetic regions. Our analysis shows that suprathermal electron PADs evolve from an almost isotropic outside the diamagnetic cavity to a field-aligned distribution near the boundary. Electron transport becomes chaotic and non-adiabatic when electron gyroradius becomes comparable to the size of the magnetic field line curvature, which determines the upper energy limit of the flux variation. This study is based on Rosetta observations at around 200 km cometocentric distance when the comet was at 1.24 AU from the Sun and during the southern summer cometary season.
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| 10. |
- Martin-Torres, Javier, et al.
(författare)
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The HABIT (HabitAbility: Brine Irradiation and Temperature) environmental instrument for the ExoMars 2022 Surface Platform
- 2020
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- The HABIT (HabitAbility: Brine Irradiation and Temperature) instrument is a European payload of the ExoMars 2022 Surface Platform Kazachok that will characterize the present-day habitability at its landing place in Oxia Planum, Mars. HABIT consists of two modules: (i) EnvPack (Environmental Package) that monitors the thermal environment (air and ground), the incident ultraviolet radiation, the near surface winds and the atmospheric dust cycle; and (ii) BOTTLE (Brine Observation Transition To Liquid Experiment), an In-situ Resource Utilization instrument to produce liquid water for future Mars exploration. BOTTLE will be used also to investigate the electrical conductivity properties of the martian atmosphere, the present-day atmospheric-ground water cycle and to evaluate if liquid water can exist on Mars in the form of brines, and for how long. These variables measured by HABIT are critical to determine the present and future habitability of the martian surface. In this paper, we describe in detail the HABIT instrument and sensors, together with the calibration of its Flight Model (FM) and the Engineering Qualification Model (EQM) versions. The EnvPack module has heritage from previous missions operating on the surface of Mars, and the environmental observations of its sensors will be directly comparable to those delivered by those missions. HABIT can provide information of the local temperature with ±0.2 °C accuracy, local winds with ±0.3 m/s, surface brightness temperature with ±0.8 °C, incident UV irradiance with 10% error of its absolute value in the UV-A, UV-B, UV-C ranges, as well as in the total UV-ABC range, and two additional wavebands, dedicated to ozone absorption. The UV observations can be used to derive the total opacity column and thus monitor the dust and ozone cycles. BOTTLE can demonstrate the hydration state of a set of four deliquescent salts, which have been found on Mars (calcium chloride, ferric sulphate, magnesium perchlorate and sodium perchlorate) by monitoring their electric conductivity (EC). The EC of the air and the dry salts under Earth ambient, clean room conditions is of the order of 0.1 μScm−1. We have simulated HABIT operations, within an environmental chamber, under martian conditions similar to those expected at Oxia Planum. For dry, CO2 atmospheric conditions at martian pressures, the air EC can be as low as 10−8 μScm−1, however it increases with the relative humidity (RH) percentage. The laboratory experiments show that after an increase from 0 to 60% RH within a few hours, the EC of the air increased up to 10−1 μScm−1, magnesium perchlorate hydrated and reached values of 10 μScm-1, whereas calcium chloride deliquesced forming a liquid state with EC of 102 μScm−1. HABIT will operate with a regular cadence, through day and night. The Electronic Unit (EU) is protected with a heater that is activated when its temperature is below −33 °C and disabled if the temperature of the surface platform rises above −30 °C. Additionally, the heaters of the BOTTLE unit can be activated to dehydrate the salts and reset the experiment. HABIT weighs only 918 g. Its power consumption depends on the operation mode and internal temperature, and it varies between 0.7 W, for nominal operation, and 13.1 W (when heaters are turned on at full intensity). HABIT has a baseline data rate of 1.5 MB/sol. In addition to providing critical environmental observations, this light and robust instrument, will be the first demonstrator of a water capturing system on the surface of Mars, and the first European In-Situ Resource Utilization in the surface of another planet.
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