Calathus: A sample-return mission to Ceres

Ceres, as revealed by NASA's Dawn spacecraft, is an ancient, crater-saturated body dominated by low-albedo clays. Yet, localised sites display a bright, carbonate mineralogy that may be as young as 2 Myr. The largest of these bright regions (faculae) are found in the 92 km Occator Crater, and would have formed by the eruption of alkaline brines from a subsurface reservoir of fluids. The internal structure and surface chemistry suggest that Ceres is an extant host for a number of the known prerequisites for terrestrial biota, and as such, represents an accessible insight into a potentially habitable “ocean world”. In this paper, the case and the means for a return mission to Ceres are outlined, presenting the Calathus mission to return to Earth a sample of the Occator Crater faculae for high-precision laboratory analyses. Calathus consists of an orbiter and a lander with an ascent module: the orbiter is equipped with a high-resolution camera, a thermal imager, and a radar; the lander contains a sampling arm, a camera, and an on-board gas chromatograph mass spectrometer; and the ascent module contains vessels for four cerean samples, collectively amounting to a maximum 40 g. Upon return to Earth, the samples would be characterised via high-precision analyses to understand the salt and organic composition of the Occator faculae, and from there to assess both the habitability and the evolution of a relict ocean world from the dawn of the Solar System.The attached document is the authors’ final accepted version of the journal article provided here with a Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Creative Commons Licence. You are advised to consult the publisher’s version if you wish to cite from it.

On the Relationship Between Energetic Electron Precipitation and Mesopause Temperature

Energetic Particle Precipitation (EPP) can potentially change the neutral atmospheric temperatureat the mesopause region. Cresswell-Moorcock et al. (2013) used European IncoherentScatter Scientific Association (EISCAT) radar data to identify strong electron precipitationevents. Here we use a similar approach and search for electron precipitation events to investigatethe simultaneous and co-located neutral temperature measurements. The temperature ofthe excited hydroxyl (OH) molecules is representative for the neutral air temperature at theheight of the OH layer, assuming there is local thermodynamical equilibrium.We use electron density datasets from the EISCAT Svalbard radar ranging from a historicaldata set from the International Polar Year (IPY) in 2007-2008, when EISCAT Svalbard radarwas run continuously, up to February 2019. Following Cresswell–Moorcock et al. (2013)particle precipitation events are characterized by a rapid increase of the electron density by afactor of 5 at an altitude range of 80-100 km. To determine the neutral temperature, we useairglow data. Spectrometer measurements of OH airglow are collected at Kjell Henriksen-Observatory (KHO), only about 1 km away from the radar site. The neutral temperatures areaveraged over one hour and half an hour and are available since the IPY.The study shows different temperature responses to EPP, which are classified accordingly.Most events show an initial decrease in the order of 20 K. The temperature decrease maymean that the EPP ionisation changes the chemical composition in the mesosphere anddecreases the population of excited OH at the top of the layer. As a consequence, theairglow peak height changes and the temperatures are probed at lower altitudes. SporadicE-layers were additionally captured by the automatic routine to search for electron densityenhancements and were examined separately. The response of sporadic E-layers on themesopause temperature at the onset is comparable to the ones for EPP, even though thedecrease in temperature is smaller than for EPP.Energetisk partikelprecipitation (EPP) kan potentiellt ändra atmosfärstemperaturen i mesopausområdet.Cresswell-Moorcock et al. (2013) använde radardata från European Incoherent ScatterScientific Association (EISCAT) för att identifiera fall av stark elektronprecipitation. Häranvänder vi ett liknande tillvägagångssätt. Temperaturen hos exciterade hydroxylmolekyler(OH) är representativ för temperaturen av den neutrala atmosfären vid OH-skiktets höjd,förutsatt att lokal termodynamisk jämvikt gäller.Vi använder observationer av elektrontäthet med hjälp av EISCAT Svalbardradar från ochmed ett historiskt dataset från det internationella polaråret (IPY) 2007–2008, fram till februari2019. Som hos Cresswell-Moorcock et al. (2013), kännetecknas fall av elektronprecipitationav en snabb ökning av elektrontätheten i ett höjdintervall av 80–100 km. För att bestämmaden neutrala atmosfärens temperatur använder vi observationer av luftsken (engl. Airglow).En spektromäter observerar spekra av OH-luftsken vid Kjell Henriksen-observatoriet (KHO),endast cirka 1 km från radarplatsen. Temperaturdata kan fås från spektra medelvärdesbildadeen timme, samt en halvtimme och är tillgängliga sedan IPY.Studien visar olika temperaturreaktioner på EPP. De flesta händelserna visar en initial minskningi storleksordningen 20 K. Temperaturminskningen kan innebära att EPP-joniseringenförändrar den kemiska kompositionen i mesosfären, vilket minskar populationen av exciteradOH vid toppen av skiktet. Som en konsekvens förändras topphöjden för airglow och temperaturermäts vid lägre höjder. Sporadiska E-skikt fångades dessutom av den automatiskarutinen för att söka efter elektrondensitetsförbättringar och undersöktes separat. Reaktionenav sporadiska E-skikt på mesopaustemperaturen vid starten är jämförbar med de för EPP,även om temperaturminskningen är mindre än för EPP

On the relationship of energetic particle precipitation and mesopause temperature

Abstract. Energetic particle precipitation (EPP) has the potential to change the neutral atmospheric temperature in the mesopause region. However, recent results are inconsistent, leaving the mechanism and the actual effect still unresolved. In this study we have searched for electron precipitation events and investigated a possible correlation between D-region electron density enhancements and simultaneous neutral temperature changes. The rotational temperature of the excited hydroxyl (OH) molecules is retrieved from the infrared spectrum of the OH airglow. The electron density is monitored by the European Incoherent Scatter Scientific Association (EISCAT) Svalbard Radar. We use all available experiments from the International Polar Year (IPY) in 2007–2008 until February 2019. Particle precipitation events are characterized by rapid increases in electron density by a factor of 4 at an altitude range of 80–95 km, which overlaps with the nominal altitude of the infrared OH airglow layer. The OH airglow measurements and the electron density measurements are co-located. Six of the 10 analysed electron precipitation events are associated with a temperature decrease of 10–20 K. Four events were related to a temperature change of less than 10 K. We interpret the results in terms of the change in the chemical composition in the mesosphere. Due to EPP ionization the population of excited OH at the top of the airglow layer may decrease. As a consequence, the airglow peak height changes and the temperatures are probed at lower altitudes. The observed change in temperature thus depends on the behaviour of the vertical temperature profile within the airglow layer. This is in agreement with conclusions of earlier studies but is, for the first time, constructed from electron precipitation measurements as opposed to proxies. The EPP-related temperature change recovers very fast, typically within less than 60 min. We therefore further conclude that this type of EPP event reaching the mesopause region would only have a significant impact on the longer-term heat balance in the mesosphere if the lifetime of the precipitation was much longer than that of an EPP event (30–60 min) found in this study

Ionospheric plasma structuring in relation to auroral particle precipitation

Auroral particle precipitation potentially plays the main role in ionospheric plasma structuring. The impact of auroral particle precipitation on plasma structuring is investigated using multi-point measurements from scintillation receivers and all-sky cameras from Longyearbyen, Ny-Ålesund, and Hornsund on Svalbard. This provides us with the unique possibility of studying the spatial and temporal dynamics of the aurora. Here we consider three case studies to investigate how plasma structuring is related to different auroral forms. We demonstrate that plasma structuring impacting the GNSS signals is largest at the edges of auroral forms. Here we studied two stable arcs, two dynamic auroral bands, and a spiral. Specifically for arcs, we find elevated phase scintillation index values at the poleward edge of the aurora. This is observed for auroral oxygen emissions (557.7 nm) at 150 km in the ionospheric E-region. This altitude is also used as the ionospheric piercing point for the GNSS signals as the observations remain the same regardless of different satellite elevations and azimuths. Further, there may be a time delay between the temporal evolution of aurora (e.g., commencement and fading of auroral activity) and observations of elevated phase scintillation index values. The time delay could be explained by the intense influx of particles, which increases the plasma density and causes recombination to carry on longer, which may lead to a persistence of structures – a “memory effect”. High values of phase scintillation index values can be observed even shortly after strong visible aurora and can then remain significant at low intensities of the aurora

Characterization of Jason-3 Spacecraft Surface Charging in LEO Polar Regions From AMBER Observations

International audienceWe have characterized spacecraft charging events in low Earth orbit (LEO) polar regions with the Active Monitor Box of Electrostatic Risk (AMBER) instrument onboard the Joint Altimetry Satellite Oceanography Network-3 (Jason-3) ocean topography mission for the first time for this spacecraft. AMBER data, taken at an altitude of 1336 km, over the period January 2017-March 2020, with measurements recorded close to the current solar minimum have been analyzed, using systematic filtering of ions spectrograms with selected threshold energies and time windows to detect negative spacecraft charging events; 109 spacecraft charging events were found. The events are examined visually and characterized by their spatial and temporal location, duration, and intensity (e.g., spacecraft potential). At the Jason-3 altitude (1336 km), the ion signature predominately lasts under 30 s in conjunction with auroral inverted V crossings, while intense fluxes of electrons corresponding to the encounter of the discrete auroral region last between 30 s and 1 min. Most of the detected spacecraft charging events show charging levels between −30 and −1000 V. The spacecraft charging events are located in the magnetic local time (MLT) sector 17h-05h, predominately before midnight. The distribution is equal between the northern and southern hemispheres. We found a high correlation between the charging time profile and that of the auroral electron average energy and energy flux along the satellite path. Overall statistics over three years as well as different event morphologies, electron spectra, and comparisons to worst case electron flux spectral distributions are presented and discussed

M5 — Mars Magnetospheric Multipoint Measurement Mission: A multi-spacecraft plasma physics mission to Mars

Mars, lacking an intrinsic dynamo, is an ideal laboratory to comparatively study induced magnetospheres, which can be found in other terrestrial bodies as well as comets. Additionally, Mars is of particular interest to further exploration due to its loss of habitability by atmospheric escape and possible future human exploration. In this context, we propose the Mars Magnetospheric Multipoint Measurement Mission (M5), a multi-spacecraft mission to study the dynamics and energy transport of the Martian induced magnetosphere comprehensively. Particular focus is dedicated to the largely unexplored magnetotail region, where signatures of magnetic reconnection have been found. Furthermore, a reliable knowledge of the upstream solar wind conditions is needed to study the dynamics of the Martian magnetosphere, especially the different dayside boundary regions but also for energy transport phenomena like the current system and plasma waves. This will aid the study of atmospheric escape processes of planets with induced magnetospheres. In order to resolve the three-dimensional structures varying both in time and space, multi-point measurements are required. Thus, M5 is a five spacecraft mission, with one solar wind monitor orbiting Mars in a circular orbit at 5 Martian radii, and four smaller spacecraft in a tetrahedral configuration orbiting Mars in an elliptical orbit, spanning the far magnetotail up to 6 Mars radii with a periapsis within the Martian magnetosphere of 1.8 Mars radii. We not only present a detailed assessment of the scientific need for such a mission but also show the resulting mission and spacecraft design taking into account all aspects of the mission requirements and constraints such as mass, power, and link budgets. Additionally, different aspects of the mission programmatics like a possible mission timeline, cost estimates, or public outreach are shown. The common requirements for acceptance for an ESA mission are considered. The mission outlined in this paper was developed during the Alpbach Summer School 2022 on the topic of “Comparative Plasma Physics in the Universe”