bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental investigation of impact cratering on Phobos
Authors: Avdellidou Chrysa , Finch Ethan , Spathis Vassi , Tandy Jon , Wozniakiewicz Penelope , Alesbrook Luke , Burchell Mark
Published: July 2024

JAXA’s Martian Moon eXploration (MMX) sample return mission aims to solve the long-debated origin of Martian moons Phobos and Deimos [1].This will be the first attempt to sample an object that either formed in the outer solar system and implanted [2,3] into the terrestrial planet region by a major dynamical process (the first origin scenario); or formed from a large impact and subsequently accumulated material from two, very possibly compositionally different, bodies, i.e. Mars and the impactor (the second scenario). In either scenario, impact processes by asteroids, meteoroids as well as Martian eject have altered the surfaces of the Martian moons and require investigation to study several aspects such as the crater formation and exposure of fresh sub-surface material, the comminution of surface boulders and regolith production, and the delivery of exogenous materials. To provide a frame for the MMX data interpretation, a laboratory experimental campaign is proposed simulating the impact processes on Phobos. We will present the preliminary results of our laboratory investigation of impact experiments using Phobos simulant materials at the Impact Lab of the University of Kent.Acknowledgements: We acknowledge CNES and ESA-OSIP funding for initiating this work. References:1. Usui et al. Space Science Reviews 216, Issue 4, article id.49 (2020). 2. Levison et al. Nature 460, Issue 7253, pp. 364-366 (2009). 3. Vokrouhlicky, Bottke, Nesvorny. The Astronomical Journal 152, Issue 2, article id. 39, 20 pp. (2016).
Radar Blackouts at Mars and Solar Energetic Particles: The Low Altitude Ionisation Layer
Authors: Lester Mark , Sanchez-Cano Beatriz , Joyce Simon , Meggi Dikshita , Stergiopolou Katerina , Opgenoorth Hermann , Lillis Robert , Witasse Olivier , Orosei Roberto , Cartacci Marco , Harada Yuki
Published: July 2024

We present observations of a low-altitude nightside ionisation layer in the Martian ionosphere during a period of Solar Energetic Particle induced radar blackout.  The interval, in December 2014, has an unprecedented coverage of data from the MARSIS Advanced Ionospheric Sounder (AIS) onboard Mars Express.  The orbit of Mars Express is ideal during this interval as it has periapsis close to the terminator and spends much of the AIS observational period on the nightside, where the layer is observed to form.  During the SEP period, the surface return signal is lost as a result of absorption of the radar signal along its path to and from the surface.  This absorption appears to have been caused by a low-altitude layer of ionisation created by the SEP event.  The AIS observed an ionospheric trace, unusual for the nightside, which we interpret as evidence for the low-altitude layer.  We demonstrate the variation of the peak electron density of this layer as a function of time and the SEP electron and ion energy flux.  We conclude that although the ions may have played a role in the creation of this layer, the electrons are most likely the major cause. 
Directly imaging massive planets sculpting the inneredges of debris discs with JWST-MIRI
Authors: James Andrew
Published: July 2024

Directly imaged debris discs can be a signpost in the darkness for finding exoplanets; those with sharp inner edges can be evidence for exoplanets, and can be responsible for sculpting these inner edges. All three targets in our JWST Cycle 1 proposal, HD202628, HD21997, and GJ14, have well-resolved ALMA imaging and all show evidence of having sharp inner edges. With the goal of utilising the deep mid-infrared sensitivity of the JWST-MIRI instrument, we used pre-launch performance estimates to customise our observations to be sensitive to sub-Jovian mass companions. In this talk, I will present these MIRI coronagraphic observations at 11.4 microns with emphasis on the new detection parameter space we cover and the sensitives we reach utilising the streamlined python package SpaceKLIP. Although our results have shown no evidence for planets down to ∼ 1MJup in all cases, combined with other factors such as proper motion anomalies - which we are exploring in our JWST Cycle 2 proposal - we can place important constraints on the presence of any bodies that might be responsible for these sharp inner edges.
Influence of a subsurface ocean on the Cassini States and the polar motion of the Galilean satellites
Authors: Coyette Alexis , Baland Rose-Marie , Van Hoolst Tim
Published: July 2024

The Galilean satellites are in an equilibrium rotation state called Cassini State and characterized by a synchronous rotation and a precession rate of the rotation axis that is equal to that of the normal to the orbit. Moreover, the spin axis of the satellite, the normal to its orbit and the normal to the inertial plane remain coplanar and the obliquity (angle between the normal to the orbit and the spin axis) remains theoretically constant over time. For satellites with a slow orbital precession rate like the Galilean moons, up to four Cassini states are possible, characterized by an obliquity close to 0 (CSI), ± π/2 (CSII and IV) and  π (CSIII). The Galilean satellites are assumed to be in CSI.We here study the influence of a subsurface ocean on the CSI of triaxial satellites using an angular momentum approach. In our model, the motion of the spin motion in space is coupled with the polar motion of the satellite and we extend our model by considering terms up to order 2 in small quantities. Moreover, and contrary to what is usually done in the classical Cassini States studies, we here do not average the external gravitational torque over short period terms. In addition to the mean obliquity value of the different satellites, we therefore also compute the nutations (small periodic variations), both in obliquity and in longitude, that arise due to the periodic variations of the gravitational torque acting on the satellites and study the influence of a subsurface ocean on the obliquity and polar motion of these satellites.
Svalbard Permafrost Landforms as Analogues for Mars (SPLAM): Scientific outcomes and outlook   
Authors: Johnsson Andreas , Hauber Ernst , Hiesinger Harald , Scmedemann Nico , Johantges Adam , Sassenroth Cynthia , Bucher Tilman , Gessner Matthias
Published: July 2024

We have been conducting Earth-analog studies for Mars in Svalbard since 2008. The program includes qualitative studies of individual landforms, mapping efforts, and long-term monitoring studies. We have acquired high-resolution aerial datasets covering the years 2008, 2020, and 2024 of selected key regions in Svalbard. Data include the visual, NIR, thermal, and high-resolution DEMs. Interpretations using remote sensing have been accompanied by annual ground truth. Fieldwork involves structure-from-motion techniques, kite imagery, and measuring several weather and soil parameters during the active warm season. We will showcase some of the outcomes of previous studies and provide an outlook on the seasons to come.   
Hiding in Plain Sight: Searching for Evidence of Subduction on Europa's Icy Shell
Authors: Kim Hyunseong , Grima Antoniette , Daly Luke
Published: July 2024

Satellite images from Voyager 1/2 and Galileo indicate that the Jovian moon Europa has a geologically young surface (40-90 Myr) and might host active tectonics within its icy shell. Previous work has interpreted many of the surface features on Europa as evidence of extensional deformation. However, outside the relatively smooth and asymmetric subsumption bands, evidence of compressional topography is very limited. This suggests that compression induced topographic uplift on Europa must be either; a) very diffuse, potentially due to the elastic properties of the ice, b) undetectable in current satellite images due to photoclinometry and resolution limitations, or c) some of the ice mass must subduct below the surface. To investigate this hypothesis, we first calculate the total volume of new ice that is generated at extension bands and rifts for a first order approximation of the expected amount of compressional uplift, assuming icy shell mass conservation and considering isostatic balance. Using the finite element code ASPECT, we will then run visco- elastic-plastic numerical models of subduction to investigate whether any ‘missing’ topographic signal can result from the subduction of ice and its associated (diffuse) compressional deformation at subsumption bands. Our results have the potential to unravel the mystery of Europa’s topography and provide new insights into the tectonics of icy planetary bodies.
Testing the vortex hypothesis in a protoplanetary disk
Authors: Ma Xiaoyi , Dong Ruobing
Published: July 2024

The HD34282 is a protoplanetary disk that hosts an azimuthal asymmetry in the mm dust continuum observed by ALMA. The asymmetry coincides with a one-arm spiral and shadow on the outer disk in near-infrared scattered light, which is coherent with signatures of a vortex shown in simulations. HD34282 thus one of few disks with solid evidence for the presence of a vortex in both NIR and mm observations. The presence of vortices is key to planet formation since they are prime sites to form planetesimals and the potential birthplace of the planets. In our work, we aim to further test the vortex hypothesis for HD34282 by examining two additional theoretical predictions for vortices: i) smaller dust traced at shorter wavelengths is less concentrated azimuthally than larger dust traced at longer wavelengths; ii) dust at the vortex center can reach a maximum dust size of several mm, one order of magnitude or larger than that in the background rings. This is done by carrying out high-resolution multi-wavelength dust continuum observations. We will compare the azimuthal extent of the structure at multiple wavelengths and constrain the dust properties via multi-wavelength spectral energy distribution modelling. Once two predictions are verified, this project will have the potential to provide the most definitive verification of a vortex in a protoplanetary disk and associate the azimuthal asymmetries mm continuum observation with vortices. On the other hand, the negative result would challenge the current theory and motivate alternative explanations for both azimuthal asymmetries in the mm continuum and one-arm spirals in NIR.
Exploring Polygonal Patterned Grounds in the Hyper-arid Atacama Desert: Insights into Formation Mechanisms and Implications for Martian Analogues
Authors: Anderson Josephine , Sager Christof , Airo Alessandro , Miedtank Andrea , Schwonke Franziska , Feige Jenny
Published: July 2024

Understanding the formation mechanisms of polygonal patterned grounds in hyper-arid environments like the Atacama Desert is crucial for unraveling their significance as an analogue for extraterrestrial landscapes, notably Mars. Unlike their extensively studied periglacial counterparts, the genesis of hyper-arid polygons requires more detailed exploration, since multiple processes, such as, desiccation [1] (including gypsum dehydration), thermal contraction [2], and haloturbation [3] are currently under debate. Therefore, we excavated a trench in polygonated ground in the Yungay area of the Atacama Desert and systematically collected over 80 soil samples covering an entire polygon, its adjacent sand wedges, and underlying sediments (190 x 190 cm). Sedimentological and geochemical analyses indicate a continuous interplay of atmospheric salt deposition, dissolution, precipitation, and inducing clast heave and shattering, under extreme dry conditions. Our findings emphasize that polygons in the Atacama Desert provide a promising analogue to Martian saline polygons, emphasizing the relevance of terrestrial studies for advancing our understanding of extraterrestrial landscapes.References:1 Ewing 2006² Sager 2021³ Zineabelidin 2024 (preprint)
Compositional variations within the TRAPPIST-1 planets
Authors: Thamm Alexander , Balduin Alexander , Carone Ludmila , Noack Lena
Published: July 2024

Since stars and their planetary accretion disks are formed by the collapse of the same interstellar dust cloud, the composition of a star can be used as a first estimate for the upper limit of the composition of the accretion disk. However, the stellar composition of TRAPPIST-1 has not yet been determined. We therefore derive elemental abundances for the main planet-forming elements from the stellar metallicity using large-scale astronomical surveys (GALAH and Hypatia).  We then apply a stoichiometric model extended from Bitsch & Battistini (2020) to obtain a first-order estimate on the compositional variation of planetary building material depending on the local temperature within an accretion disk. In this approach, the gas within the accretion disk is assumed to have achieved the state of chemical equilibrium before condensation, with the complete set of molecules preexisting in the gas. Consequently, the relative abundance of molecules can be calculatedstochiometrically and based on their condensation temperature (Lodders 2003). We assume a fixed temperature profile within the accretion disk and do not consider planet migration to obtain a first prediction of compositional variability within the TRAPPIST-1 accretion disk. Our predicted composition of the planetary building blocks of the seven planets in the system is shown in Fig. 1. We obtain three different compositional clusters including dominantly dry (b,c,d), water-rich (e,f) and water- and ammonium-rich building blocks.  We then apply our interior-structure model (Noack et al. 2016) employing look-up tables created with Perple_X (Connolly 2009) for thermodynamic properties of the silicate mantles. We apply an Earth-like mantle iron number of 0.1 (i.e. a magnesium number of 0.9) for the silicate mantle, which leads to a predicted core-mass fraction of 25% for the three inner-most planets (Carone et al. in review). This core-mass fraction leads to planet radii matching the observed values from Agol et al. (2021) for all thre planets, which suggests, that our compositional model is able to correctly predict the planetary composition of the TRAPPIST-1 planets and that their composition was not strongly altered during accretion (by e.g. impact erosion).  For the outer planets of the system, the appearance of volatiles adds a degeneracy to our interior structure, since melting processes during planet accretion implies volatile losses. The final planetary composition is therefore expected to be considerably less volatile-rich than predicted here for the planetary building blocks. Assuming the same mantle-core composition as for the three inner-most planets, our model suggests that the outer planets should have a maximum water fraction below 20 wt-% to match their observed radii, which is in accordance with earlier studies, even though here we apply our TRAPPIST-1 adapted compositional model instead of an Earth-like mineralogy.  
Direct imaging of exoplanets with JWST/MIRI
Authors: Boccaletti Anthony , Mâlin Mathilde , Rouan Daniel , Perrot Clément , Lagage Pierre-Olivier , Lagrange Anne-Marie , Charnay Benjamin , Pierre Baudoz
Published: July 2024

JWST has opened a completely new spectral range in the mid IR for the study of exoplanetary systems which promise to offer unprecedented results both in terms of characterization but also discovery space.  Two observing modes in MIRI are of particular interest : 1) the coronagraphic mode installed in the imager made of four independent coronagraphic masks paired with dedicated filters covering the ~10 to ~20 microns window, and 2) the Medium Resolution Spectrograph which has a much wider spectral range from 5 to 28 microns but without coronagraphic capacity.  We will first describe these two modes and their respective performances, based on actual observations or from simulations. Then we will present the first results from the exoplanet Guaranteed Time Observations team of the MIRI consortium, focusing for instance on the multiplanet system HR8799 (see figure 1 and 2), and highlight some results obtained from General Observers programs. Finally we will discuss the broad interest of MIRI for science cases like cold planets at large orbital separations as well as protoplanets.   Figure 1 : Raw coronagraphic and reference star subtracted images of the multiple planet systems HR8799 obtained with MIRI in 4 different filters at mid IR wavelenghts.   Figure 2: spectral energy distribution of planet HR8799 b compared to 2 atmospheric models fitted on near IR and mid IR photometric data points.   
Guiding and Target Acquisition for the Ariel Space Mission: Algorithms and Performance
Authors: Mösenlechner Gerald , Ottensamer Roland , Kerschbaum Franz
Published: July 2024

Nothing in space is ever truly stable. For space telescopes such as Ariel, this leads to a noise source in photometric and spectroscopic measurements caused by the movement of the target star or spectra (also refereed to as jitter) across the detectors inconsistent pixels. In order to minimise this source, continuously guiding the telescope becomes a necessity. Ariel will perform both photometric and spectroscopic observations of transiting exoplanets across multiple phases of their orbit in order to study the chemical composition of their atmosphere. Given the long duration of these observations, an unstable pointing of the telescope would add significant noise to the time series of the measurements. Therefore, Ariel is equipped with a dedicated instrument: the Fine Guidance Sensor (FGS). While the FGS is a scientific instrument that provides both low-resolution spectra and photometry in bands specific to atmospheric molecular features, it also doubles as an input for the closed loop guiding of the telescope. For this task, the FGS uses two of its three photometric channels to measure the position of the target star at a rate of 10 Hz. This positional information is then sent to the spacecrafts Attitude and Orbit Control System (AOCS), which applies the necessary corrections using the platforms actuators. In order to obtain the necessary measurements, the FGS will be equipped with dedicated guiding algorithms as part of its Instrument Application Software (IASW), which is developed by the University of Vienna.In this paper we present the current state of the design of these methods. The algorithms are split into Target Acquisition and Tracking, where the former is used to correctly identify the star on a large field of view. On the other hand, Tracking is used during the scientific observations of the target in order to keep the instruments line of sight as stable as possible. In addition to the design and implementation of these algorithms, we also discuss their performance and our tools for their evaluation and testing. The images we use for performance testing are generated using our own simulators. These simulators are able to properly represent the noise sources we expect in the real instrument such as detector noise, line of sight jitter and smearing. Additionally, the simulators are designed to be as fast as possible to allow their reuse in closed loop testing, both in simulation environments and using real hardware.
Using debris disk observations to infer exoplanets orbiting within or outside a planetesimal belt
Authors: Stuber Thomas , Löhne Torsten , Wolf Sebastian
Published: July 2024

We analyzed the potential to infer the presence of an exoplanet via spatially resolved observations of a coexisting debris disk.Using numerical simulations, we investigated the observable effects on a cold debris disk that are caused by secular gravitational perturbations. The perturbations originate from an exoplanet on an eccentric orbit either within (~ 40 au) or outside (~ 500 au) the planetesimal belt. We identified features in the resulting brightness distributions that are suitable to distinguish between those two types of systems and showed that these features are possibly detectable with present observatories, especially with combined observations using JWST/MIRI and ALMA.
Dimensionality reduction on MIR spectra of powdered silicate glasses as analogues for volcanic ashes
Authors: Baroni Marco , Pisello Alessandro , Petrelli Maurizio , Perugini Diego
Published: July 2024

Rationale Silicate glasses are significant components of volcanic products, but spectral libraries typically provide references of crystalline materials rather than amorphous ones, even if blurred/featureless spectra are observed on planetary terrains. Thus, the Petro-Volcanology Research Group (PVRG) started an investigation of the spectral response of silicate glasses developing a database, to distribute spectral data applying the FAIR (Findable, Accessible, Interoperable, Reusable) principles ​[1]​. We have analyzed these spectra using PCA and, in particular, we focused on MIR range, in which information about silicates’ arrangement in the material is detectable ​[2].Fig. 1: a) TAS diagram of all products. Circles:sub-alkaline , triangles:  alkaline. b) spectra of the entire dataset MethodologyThe investigated datasets consist of MIR spectra of 20 powdered silicate glasses (
ESCAPADE Update: unraveling cause and effect in Mars’ hybrid magnetosphere
Authors: Xu Shaosui , Lillis Robert , Curry Shannon , Hara Takuya , Curtis David , Taylor Ellen , Courtade Sarah ,   ESCAPADE Team
Published: July 2024

Multi-spacecraft missions after 2000 (Cluster II, THEMIS, Van Allen Probes, and MMS) have revolutionized our understanding of the causes, patterns and variability of a wide array of plasma phenomena in the terrestrial magnetospheric environment. ESCAPADE is a twin-spacecraft Mars mission concept that will similarly revolutionize our understanding of how solar wind momentum and energy flow throughout Mars’ magnetosphere to drive ion and sputtering escape, two processes that have helped shape Mars’ climate evolution over solar system history.ESCAPADE will measure magnetic field strength and topology, ion plasma distributions as well as suprathermal electron flows and thermal electron and ion densities, from precessing elliptical 150 x ~8500 km orbits. ESCAPADE are small spacecraft (
Mercury's tidal Love number h2 from co-registration of reprocessed MLA profiles
Authors: Xiao Haifeng , Stark Alexander , Steinbrügge Gregor , Briaud Arthur , M. Lara Luisa , J. Gutierrez Pedro
Published: July 2024

Due to its eccentric orbit, Mercury experiences varying gravitational pull from the Sun along its orbital course, leading to periodic tidal deformation, i.e, stretching and squeezing of the planet. Prectically speaking, Mercury’s surface will rise “up and down” periodically. The magnitude of these surface height variations, typically quantified by the tidal Love number h2, depends on properties of the deep interior.  A reliable measurement of the tidal h2 can thus shed crucial insights into Mercury’s interior structure, especially the size and physical state of its core.  The estimation of the tidal deformation requires laser or radar altimetric measurements. So far, the tidal h2 of Mercury has only been measured by Bertone et al. (2021) through minimizing height misfits at the intersection points, cross-overs, of the Mercury Laser Altimeter (MLA) profiles. However, only their lower bound is consistent with the existing modeling results (Steinbrügge et al., 2018; Goossens et al., 2022; Figure 1).In this study, we look into Mercury's tidal deformation by applying an alternative approach to reprocessed MLA profiles, which is based on the co-registration techniques. Previously, we have successfully applied these techniques to Mars Orbiter Laser Altimeter (MOLA) profiles to obtain the spatio-temporal thickness variations of the seasonal CO2 snow/ice at Martian polar regions (Xiao et al., 2022a, b). By employing the co-registration procedures to the MLA profiles, the interpolation errors associated with the usage of cross-overs are avoided. During the reprocessing to improve the profiles’ geolocation, we correct for a pointing aberration due to relativity effects (Xiao et al., 2021) and incorporate an updated spacecraft orbit model that has better accounted for the non-gravitational forces (Andolfo et al., 2024). We carry out the study at the very polar region of 77°N to 84°N where footprints are the densest and off-nadir pointing angles are generally the smallest. For verification of the proposed approach and quantification of its uncertainty, we generate realistic synthetic profiles and conduct extensive simulations. We obtain a tidal h2 of 0.92±0.51 (3-sigma), with a central value 0.63 smaller than that of Bertone et al. (2021, 1.55±0.65), but compatible with existing models (Figure 1). Combined with the most recent gravitational deformation measurements, our measured tidal h2 favors a small to medium-sized solid inner core (
ExoClock Unlocked: Fostering Public Engagement in Exoplanet Research
Authors: Pantelidou Georgia , Kokori Anastasia
Published: July 2024

ExoClock Unlocked, an initiative of the ExoClock project team, aims to democratize the field of exoplanet research by enabling public participation in support of ESA’s Ariel space mission. The project has been running for two years and participants get the opportunity to observe exoplanet transits by using remote observing facilities. ExoClock Unlocked invites all exoplanet enthusiasts, regardless of their previous experience, that don’t have access to equipment to participate in a real space mission. During the project seminars, all members engage as citizen scientists. They learn how to perform remote observations, with support from the ExoClock team, which includes scientists and public engagement specialists, and analyze the gathered data utilizing user-friendly tools. This presentation will outline the key procedures and strategies that have led to successful project outcomes. We will discuss the challenges encountered and the solutions implemented by our team, and highlight the tangible benefits realized through this inclusive scientific initiative.
Shape model of the binary NEA (385186) 1994 AW1 from 2015 radar observations and long term lightcurve dataset. 
Authors: Ferrais Marin , Marshall Sean , Venditti Flaviane , Devogèle Maxime , Pravec Petr , Scheirich Petr , Jehin Emmanuël
Published: July 2024

(385186) 1994 AW1 is a potentially hazardous asteroid, the first near-Earth asteroid suspected to be a binary [1,2] and was selected as the initial target of the DART and HERA mission. 1994 AW1 made a close approach to Earth in July 2015, getting as close as 25 lunar distances on the 15th. This flyby was a great opportunity for observations in photometry [3] and radar.Continuous wave (CW) and Delay Doppler imaging modes were used, first at Goldstone for the 14-19 July period (0.066-0.070 au), and then by Arecibo for the 20-30 July 2015 (0.075-0.126 au). A range resolution of 150 m was achieved at Goldstone in bistatic configuration with Green Bank Telescope (8560 MHz), while monostatic observation in S-band (2380 MHz, 12.6 cm) at Arecibo were obtained at resolutions of 30 m and 75 m. The rotation period of the primary (2.52 h) and orbital period of the secondary (22 h) derived from optical light curves  [4] were confirmed by these observations. The primary is about 800 m in diameter and the secondary is about half of the primary size. A more recent but relatively distant approach (July 8, 2022; 0.11 au) allowed CW spectra to be obtained at Goldstone [5].We also obtained new light curves in 13-24 January 2023 while it was at V ~16-17 mag. We used the TRAPPIST-South (I40, Chile) and -North (Z53, Morocco) [6] to gather 10 light curves in total. For 4 of them, brightness drops indicate mutual events between 1994 AW1 and its satellite.We searched for the sidereal rotation period of 1994 AW1 by combining the TRAPPIST data with data from the Ondřejov Observatory 0.65m telescope and the Danish 1.54m telescope, obtained between 2014 and 2023. We used the lightcurve inversion method of [7] and [8] and derived a convex shape model with sidereal period of 2.518586 ± 0.000011 h, a pole orientation of 187° of ecliptic longitude and +67° of ecliptic latitude, and a b/a axis ratio of 0.97.    Figure: Convex shape model of 1994 AW1 derived from lightcurve inversion and viewed along the rotation (z) axis on the left, the x axis (middle) and the y axis (right). The black arrow indicates the rotation axis.Finally, we combined our radar and optical datasets with SHAPE [9] to perform shape modeling of the primary component. We will present our preliminary non-convex 3D shape model, pole coordinates and system density. References:[1] Pravec, P. and Hahn, G. (1997), Icarus, 127.[2] Mottola, S. et al. (1995), Icarus 117, 62-70.[3] Warner D. B. (2016), MPB, 43.[4] Pravec et al. (2006), Icarus, 181, 63-93.[5] Brozovic, M. et al. (2022) DPS 54.[6] Jehin, E. et al. (2011), The Messenger 145, 2–6.[7] Kaasalainen & Torppa (2001), Icarus, 153, 24.[8] Kaasalainen, M. et al. (2001), Icarus, 153, 37.[9] Magri, C. et al. (2007), Icarus 186, 152-177.
Evolution of the ion dynamics at comet 67P during the escort phase
Authors: Lewis Zoe , Stephenson Peter , Kallio Esa , Galand Marina , Beth Arnaud
Published: July 2024

Comet 67P/Churyumov-Gerasimenko was escorted by the Rosetta spacecraft through a 2 year section of its 6 year orbit around the Sun. This enabled the observation of a large variation in comet outgassing and the resulting evolution of the plasma environment. The diamagnetic cavity, a region of negligible magnetic field arising from the interaction of the unmagnetised cometary plasma with the solar wind, began to be detected sporadically by the Rosetta Plasma Consortium/ Magnetometer (RPC/MAG) in April 2015 at a heliocentric distance of 1.8 au [1]. The last detections were in February 2016 at 2.4 au. Within this cavity, the flow of cometary ions has been shown to be largely radial [2]; the ions are accelerated above the neutral gas speed by an ambipolar electric field, but many newborn ions still undergo multiple ion-neutral chemical reactions before escaping [3,4]. Outside the diamagnetic cavity boundary, which is itself highly variable, the ion flow is considerably more complex, and the ambipolar electric field plays a more minor role compared to the convective electric field of the solar wind [2].  At large heliocentric distances (>2.5 au), the total plasma density observed from RPC plasma sensors is well explained by a simple flux conservation model that assumes the ions travel radially away from the nucleus at speed close to that of neutrals [5,6]. However, closer to perihelion and once the diamagnetic cavity has formed, such an approach does not hold [7]. We aim to better understand this transition, the driver of ions' acceleration, and the role that the diamagnetic cavity plays.In this study, we explore the varying ion dynamics both in the presence (e.g. during high outgassing activity) and absence (low outgassing activity) of a diamagnetic cavity. Electric and magnetic fields from hybrid simulations of the cometary environment are used to drive a 3D test particle model of the cometary ions for a range of comet activity levels. We model the behaviour of three key ion species, H2O+, H3O+, and NH4+, in order to assess the impact of the ion dynamics on the ionospheric composition and density. [1] Goetz et al. MNRAS S 462, S459–S467 (2016)[2] Koenders et al., Planetary and Space Science, 101-116, 105 (2015)[3] Lewis et al., MNRAS, 523, 6208–6219 (2023)[4] Lewis et al 2024, MNRAS, 530, 66–81 (2024)[5] Galand et al., MNRAS, S331-S351, 462 (2016)[6] Heritier et al., A&A, 618 (2018)[7] Vigren et al., ApJ 6, 881(1) (2019)
The influence of ammonia on the primordial distribution of volatiles in the hydrosphere of Europa
Authors: Amsler Moulanier Alizée , Mousis Olivier , Bouquet Alexis
Published: July 2024

The question of the habitable environments within the Galilean moons is raised by the presence of hydrospheres in those worlds. The study of the current volatiles inventory on those moons is indicative of their formation processes and how they could affect this inventory. However, for the ability to disentangle between the possible scenarios, it is necessary to examine the post-accretion processes that could impact the volatile inventory of the hydrospheres. Especially, an “open-ocean” phase that occurred shortly after accretion, before the icy crust formation, must be considered, in view of its influence on the volatile inventory. More specifically, the abundance of ammonia in Europa’s building blocks is a key constrain, both on the habitability conditions of the ocean and the composition of the primordial thick atmosphere of the moon.Our work focuses on modelling the ocean-atmosphere equilibrium which took place over this period, based on the type of material accreted by Europa at its formation. To do so, we compute the vapour-liquid equilibrium between water and volatiles, as well as the chemical equilibria happening within the ocean to model the primitive hydrosphere of Europa. Our model allows for an assessment of the impact of the initial distribution of volatiles resulting from the thermodynamic equilibrium between Europa’s primordial atmosphere and ocean. In particular, we show the correlation between the ratio of dissolved CO2 and NH3 and the distribution of partial pressures in the primordial atmosphere of Europa.Fig1: Evolution at T = 300 K of the distribution of species in both the atmosphere and the ocean as a function of the mole fraction of initially NH3 incorporated into the atmosphere. All the other species’ initial mole fractions remain constant.Navigating between different compositions of accreted material and varying the proportion of ammonia incorporated into the ocean after accretion, we obtain a range of primordial volatile distributions in the hydrosphere, to be linked to nowadays inventory. We also find ammonia abundance thresholds above which CO2 content is significantly depleted by NH2COO-  formation (fig 1).
Ariel detrending: algorithms to mitigate the jitter disturbance
Authors: Bocchieri Andrea , Mugnai Lorenzo V. , Pascale Enzo , Syty Angèle
Published: July 2024

The European Space Agency’s Ariel mission, scheduled for launch in 2029, aims to conduct the first large-scale survey of atmospheric spectra of transiting exo-planets. Jitter in the spacecraft’s line of sight is a source of disturbance when measuring the spectra of exoplanet atmospheres. We will describe an improved algorithm for de-jittering Ariel observations simulated in the time domain using ExoSim2, the new Exoplanet Observation Simulator, adapted to Ariel. The jitter is based on representative simulations from Airbus Defence and Space, the Ariel spacecraft’s prime contractor. We investigate the accuracy and biases of the retrieved atmospheric spectra from the jitter-detrended observations. Using our algorithm to de-jitter photometric and spectroscopic data, we will demonstrate the possibility of achieving the photon noise limited performance compliant with the mission requirements across the whole Ariel spectrum. This work contributes to the development of the data reduction pipeline for Ariel, aligning with its scientific goals, while potentially benefiting other astronomical telescopes and instrumentation.
Rotation state of asteroid (99942) Apophis and its change during the 2029 flyby
Authors: Ďurech Josef , Pravec Petr , Vokrouhlický David , Hornoch Kamil , Kušnirák Peter , Fatka Petr , Kučáková Hana
Published: July 2024

The excited non-principal axis rotation state of asteroid Apophis can be described by two periods - rotation and precession. These periods (263 h and 27.38 h, respectively), together with other spin parameters and a convex shape model, were derived by [1] from photometric observations in 2012/13. Radar observations from the same apparition are consistent with the spin state derived from light curves and suggest that the shape of Apophis might be bifurcated [2]. During another favorable apparition in 2020/21, Apophis was observed extensively, and an updated shape and spin model was derived [3].We carried out photometric observations of Apophis between November 2020 and May 2021 with the Danish 1.5m telescope at La Silla, ESO. This data set consists of 1280 calibrated photometric measurements in Cousins R filter distributed over 67 individual nights.We used all available photometric data from 2012/13 and 2020/21 to determine Apophis's spin state and convex shape with the light curve inversion method [4]. Due to the large gap of eight years between observations, the rotation parameters cannot be determined uniquely. However, all acceptable models have about the same orientation in 2029 due to the same separation of eight years between 2021 and 2029. This enables us to reliably predict Apophis attitude during the close approach in 2029 and estimate the change of its spin state caused by the Earth's gravitation torque during the encounter.Acknowledgments: This work was supported by the grant 23-04946S of the Czech Science Foundation.References: [1] Pravec P. et al. (2014) Icarus, 233, 48. [2] Brozovic M. et al. (2018) Icarus, 300, 115. [3] Lee H.-J. et al. (2022) A&A, 661, L3. [4] Kaasalainen M. (2001) A&A, 376, 302. 
The contribution of Jupiter-family comets to the fireball population
Authors: Shober Patrick , Tancredi Gonzalo , Vaubaillon Jeremie , Devillepoix Hadrien , Deam Sophie , Anghel Simon , Sansom Eleanor , Colas Francois , Martino Silvia
Published: July 2024

BackgroundJupiter-family comets (JFCs) are distinct low-inclination comets predominantly originating from the Kuiper belt and the scattered disk. These regions, extending beyond Neptune’s orbit, are home to icy primitive bodies that have retained many of their volatile components. JFCs, characterized by their short orbital periods (
Rock Specimens for Laboratory Drill and Compositional Testing for the Ma_MISS experiment onboard ESA/ExoMars Rosalind Franklin Mission to Mars
Authors: Frigeri Alessandro , De Sanctis Maria Cristina , Altieri Francesca , Ammannito Eleonora , De Angelis Simone , Ferrari Marco , Rossi Lorenzo , Valentini Giovanni , Team the Ma_MISS
Published: July 2024

The ESA ExoMars mission, which will look for traces of past and present life on Mars, is planned for 2028. The Rosalind Franklin rover will land within a 115 by 15 km ellipse centered at Oxia Planum, a gently sloped broad plain connecting the outlet of Cogoon Vallis channels with Chryse Planitia.  The Rosalind Franklin rover is equipped with a state-of-the-art drilling system capable of reaching depths 2 meters below the surface.    Next to the tip of the drill is the miniaturized spectrometer Ma_MISS, which will record the compositional variation along the drilling hole.    The combination of the advanced tool and instrument onboard Rosalind Franklin will provide us with unprecedented insights into the shallow subsurface of Mars, which we know little about but could potentially harbor life.The Ma_MISS scientific team is preparing for the ExoMars mission to Mars by studying terrestrial analogs in the field and the laboratory.   We are collecting samples from a pool of possible geological environments expected at Oxia.   We are using the recently published geologic map of the Oxia Planum ExoMars landing ellipse as a reference to select analog samples to bring to the laboratory. The samples collected in the field are stored and cataloged at the Istituto di Astrofisica e Planetologia Spaziali (IAPS) in Rome, Italy. The DAVIS (Drill for Analogues and Visible-Infrared Spectrometer) laboratory setup at IAPS will be used to drill and do compositional mapping on the samples.Here, we present the case of a set of samples acquired in a fluvial-lacustrine environment showing fossilized sedimentary structures representing an optimal environment for microbial life.    With DAVIS, we simulate the combined action of the Rosalind Franklin drill and Ma_MISS in-hole compositional analysis, building a library of experiments with different geologic settings in preparation for the actual mission.Acknowledgments:  This work is supported by the ASI-INAF Mars Exploration agreement code 2023-3-HH_0. 
The extreme ultraviolet camera and energetic neutral atomic imager onboard the Queqiao-2 satellite
Authors: Zhang Xiao-Xin , He Fei , Liu Wenlong , Sun Tianran , Zhang Xianguo , He Lingping , Chen Bo , Yu Qinglong
Published: July 2024

Energy circulation in geospace lies at the heart of space weather research. Establishing global mass and energy transportation image in the solar wind-magnetosphere coupling system is critical for space physics and space weather research. Remote sensing overcomes the difficulties of capturing global views and distinguishing spatiotemporal variations in in-situ particle and field detections. The moon is an idea platform for imaging the global magnetosphere. An extreme ultraviolet camera operating at 30.4 nm has successfully captured the global plasmaspheric images with the Chang’e-3 lunar landing mission. A new double-wavelength extreme ultraviolet camera and an energetic neutral atomic (ENA) imager have been carried by the Queqiao-2 satellite to image the magnetosheath at 30.4 nm, the plasmasphere at 30.4 nm, the ionospheric oxygen ion outflow and oxygen ion in the magnetosphere at 83.4 nm, and the ring current ENA. The two imagers will significantly benefit the investigations in solar wind-magnetosphere coupling.
Dynamics of the topside ionospheres of Venus and Mars as seen by recent radio science observations
Authors: Peter Kerstin , Pätzold Martin , Withers Paul , Ramstad Robin , Thiemann Edward , Fränz Markus , Häusler Bernd , Futaana Yoshifumi , Holmström Mats
Published: July 2024

Fig. 1: Topside ionospheres of Venus and Mars as seen by (a) VEX VeRa, (b) MEX MaRS and (c) MAVEN ROSE.radio science.While the orbital and environmental parameters of Venus and Mars show significant differences, their planetary ionospheres show notable similarities (Figure 1). The photochemically dominated regions of the undisturbed dayside ionospheres of Venus and Mars are both characterized by two major features. The ionospheric main peak region (V2 at Venus, M2 at Mars) is a result from photoionization by solar EUV irradiation. The weaker secondary V1/M1 region originates from the primary and secondary ionization of the neutral atmosphere caused by solar X-ray radiation. The upper region of the Venus and Mars dayside ionospheres is governed by transport processes.The extent and shape of the ionospheric topsides is observed with the radio science experiments Venus Express Radio Science (VeRa) onboard Venus Express (VEX) [1] at Venus and Mars Express Radio Science (MaRS) [2] onboard Mars Express (MEX) and  the Radio Occultation Science Experiment (ROSE) onboard the MAVEN spacecraft [3] at Mars. The observed electron density exhibits substantial variability on temporal scales and ranges from an undisturbed exponential decay (Fig. 1b) to strongly compressed shapes (Fig. 1a, c). This work combines 9 years of VEX-VeRa (2006-2014), 18 years of MEX-MaRS (2004-2021) and 8 years of MAVEN-ROSE (2014-2021) radio occultation observations to investigate the variability of the topside ionospheres of Venus and Mars on the planetary dayside. The derived ionospheric characteristics will be compared to accompanying observations of the solar wind dynamic pressure (from VEX-ASPERA4 [4], MEX-ASPERA3 [5, 6] and MAVEN instruments [7]), solar irradiation flux (FISM-V2 model [8], MAVEN EUV monitor [9]) and a model of the crustal magnetic field for Mars [10] to improve our understanding of the solar wind interaction of planets without a global magnetic field.References[1] Häusler et al. (2006)  PSS 54 (13-14)[2] Pätzold et al. (2004) in Fletcher (2004) Mars Express. The scientific payload. ESA[3] Withers et al. (2018)  JGR Space Phys. 123 (5)[4] Barabash et al. (2007)  PSS 55 (12)[5] Barabash et al. (2006)  SSR 126[6] Ramstad et al. (2015)  JGR Planets 120 (7)[7] Halekas et al. (2015)  SSR  195[8] Chamberlin et al. (2020) Space Weather 18 (12)[9] Thiemann et al. (2017) JGR Space Physics 122 (3)[10] Morschhauser et al. (2014)  JGR Planets 119 (6)
LimPa mission: A small mission proposal to characterize the enigmatic lunar dust exosphere
Authors: Futaana Yoshifumi , Kallio Esa , Knuuttila Olli , Nyman Leo , Shimoyama Manabu , Barabash Stas
Published: July 2024

The lunar environment is known to be characterized by complex interactions between plasma, the exosphere, dust, and the surface. However, our understanding of the environment is limited due to the lack of experimental evidence. Here we propose a small, low-cost mission to characterize the dust and exosphere environment of the Moon. Named the Limb Pathfinder (LimPa), this is a proof-of-concept mission aimed toward understanding the coupling between plasma, dust, and tenuous neutral atmosphere. The LimPa mission was proposed to a call for the Small Mission to the Moon issued by European Space Agency in 2023. LimPa is designed to examine the dust exosphere above the lunar polar regions by using an utterly novel remote-sensing technique to measure the solar wind hydrogen atoms—the solar wind protons that are neutralized to hydrogen atoms (Figure 1). Its goals are 1) to detect for the first time the neutralized solar wind hydrogen produced by exospheric gas and levitated dust; 2) to measure the height profiles of the levitated dust and exospheric gas densities; and 3) to determine the emission mechanism of the horizon glow. Our baseline design of the LimPa mission is a 12U CubeSat (Figure 2). Three highly matured instruments are used: an energetic neutral atom camera, a proton sensor, and a camera system. The LimPa CubeSat is proposed to be inserted into a circular lunar polar orbit, with an altitude of 100 km as a baseline. The Sun-pointing attitude will allow measurements of neutralized solar wind that are produced by the exosphere and dust grains above the polar regions. The nominal lifetime is for three months as a pathfinder mission. The LimPa mission will open a new window to remote characterization of the lunar dust exosphere environment above the poles, and will demonstrate that this monitoring can be achieved with a simple and low-cost instrument system and spacecraft operation. The concept to be proven by the LimPa mission will enable long-term monitoring of the fragile dust exosphere environment, which substantially impacts on lunar exploration and will be significantly altered by human activities.Figure 1: A conceptual illustration of the LimPa mission. The solar wind protons (pink trajectories) are neutralized by the exospheric gas or by the dust grains (green trajectories). By measuring these neutrals by LimPa Cubesat, we can retrieve the exosphere and dust information near the Moon.Figure 2: A conceptual design of the LimPa Cubesat (12U).
Detection of Chelyabinsk-type objects in the thermal infrared
Authors: Müller Thomas , Conversi Luca , Licandro Javier , Delbo Marco , Fitzsimmons Alan , Muinonen Karri , Popescu Marcel , Tanga Paolo , Moissl Richard
Published: July 2024

The Chelyabinsk progenitor asteroid approached Earth undetected, because its radiant was close to the Sun. In addition, the 20-m size object was very faint and very fast moving. Visible wavelength observations of such objects also suffer from the high phase angle illumination geometry. We examine this event within the framework of current and forthcoming infrared space initiatives, such as ESA’s planned NEOMIR space mission. We focus on strategies for early detection of similar objects before potential impact.
Infrared (IR) observations from space offer distinct advantages: (i) enhanced Sun-asteroid contrast compared to visible wavelengths, (ii) small, fast-rotating object are (nearly) isothermal which make IR detections at high phase angles easier, (iii) immediate good-quality size estimation upon IR detection, and (iv) feasibility of observations near the Sun.
We scrutinize the IR-detection scenario of a 20-m object on a Chelyabinsk-like orbit, acknowledging challenges such as high background levels from zodiacal light and high apparent sky motion of the targets. Our investigation addresses key questions: (1) optimal IR wavelengths for (theoretical) detection, (2) measurement strategies for high apparent motion targets, (3) practical aspects when searching for NEAs close to the Sun, (4) optimal placement of IR telescopes in space, and (5) estimated lead times for detecting Chelyabinsk-type objects before potential impact for different telescope sizes and detector integration time.