bluuebunny/crossref_metadata_2025 huggingface dataset:
MapX: An In-situ X-ray µ-Mapper for Habitability and Biosignature Studies
Authors: Blake David , Walroth Richard , Sarrazin Philippe , Bristow Thomas , Gailhanou Marc , Downs Robert , Thompson Kathleen
Published: October 2020

   Introduction: The search for evidence of life or its processes on Mars takes on two major themes: 1), the identification of environments that have or once had the potential to harbor life (habitability); and 2), the detection of morphological or chemical features suggestive of extinct or extant life (biosignatures).  Compositional heterogeneity at the mm-to-100µm scale can reveal geological processes indicative of past or present habitability, and morphological and compositional heterogeneity on a similar length scale can provide evidence of life’s processes.  The Mapping X-ray Fluorescence Spectrometer (MapX) is an arm-based in-situ instrument designed to identify these features on planetary surfaces [1]. Instrument Description: MapX is a full-field elemental imager capable of analyzing samples in situ without sample preparation. MapX has no moving parts, a 1-cm depth of field, and is designed to utilize 244Cm radioisotope sources, eliminating the need for a High Voltage Power Supply or X-ray tube.  Figure 1 shows a schematic of the instrument, which consists of X-ray / ϒ-ray / α-particle sources, a focusing optic, and a CCD. The focusing lens is an X-ray micro-pore optic (MPO) which focuses X-ray photons 1:1 onto the CCD. The MPO has a large depth of field (~1cm) allowing rough unprepared surfaces to be imaged with minimal loss of resolution. The CCD is read out fast enough (several frames per second) so that each pixel records either a single photon from the sample or background. The number of electron hole pairs generated in a single pixel is directly proportional to the energy of the X-ray photon, and after summing a large number of individual frames, an XRF spectrum is generated for each pixel of the CCD. Each individual 0.3 sec. frame is a complete image; however many frames are necessary to produce quantifiable XRF spectra. Longer collection times will allow for improved signal to noise, but in the event a collection is interrupted the partial data will still yield a complete image.  Downlinked data products include:  Elemental maps 11
Twinkle: a low-Earth orbit, visible and infrared observatory for exoplanet and solar system spectroscopy
Authors: Edwards Billy , Tessenyi Marcell , Savini Giorgio , Tinetti Giovanna , Stotesbury Ian , Archer Richard , Joshua Max , Wilcock Ben , Windred Philip , Tennyson Jonathan
Published: October 2020

The Twinkle Space Mission is a space-based observatory that has been conceived to measure the atmospheric composition of exoplanets, stars and solar system objects. The satellite is based on a high-heritage platform and will carry a 0.45 m telescope with a visible and infrared spectrograph providing simultaneous wavelength coverage from 0.5 - 4.5 μm. The spacecraft will be launched into a Sun-synchronous low-Earth polar orbit and will operate in this highly stable thermal environment for a baseline lifetime of seven years.Twinkle’s rapid pointing and non-sidereal tracking capabilities will enable the observation of a diverse array of Solar System objects, including asteroids and comets. Twinkle aims to provide a visible and near-infrared spectroscopic population study of asteroids and comets to study their surface composition and monitor activity. Its wavelength coverage and position above the atmosphere will make it particularly well-suited for studying hydration features that are obscured by telluric lines from the ground as well as searching for other spectral signatures such as organics, silicates and CO2.Twinkle is available for researchers around the globe in two ways:1) joining its collaborative multi-year survey programme, which will observe hundreds of exoplanets and solar system objects; and2) accessing dedicated telescope time on the spacecraft, which they can schedule for any combination of science cases.I will present an overview of Twinkle’s capabilities and discuss the broad range of targets the mission could observe, demonstrating the huge scientific potential of the spacecraft.
Retrieval of martian dust and cloud properties from ground-based radiance dust sensors
Authors: Toledo Daniel , Apéstigue Victor , Gómez Laura , Martinez-Oter Javier , Jiménez Juan Jose , Yela Margarita , Arruego Ignacio
Published: October 2020

On Mars, dust and clouds are primary elements for studying the interactions of solar radiation with the atmosphere and surface and their influence on the radiation balance. Depending on the dust opacity and other properties such as the particle size distribution, airborne dust can provide positive or negative radiative feedbacks into dynamical processes. This role played by dust in the circulation of the atmosphere points out the need of retrieving the dust optical properties at different time periods and locations. In order to perform these observations a number of ground-based radiance dust sensors were selected for Exomars and Mars 2020 missions (e.g. Arruego et al., Advances in Space Research, 60, 2016; Apéstigue et al., EPSC 2015). These instruments measure the solar flux at different wavelengths and sky locations along the day. From radiative transfer simulations of these observations, dust properties such as the number density or particles radius can be inferred. In this work, we will present and discuss different retrieval procedures developed for the characterization of dust and clouds on Mars.
Mars Express science highlights and future plans
Authors: Titov Dmitrij , Bibring Jean-Pierre , Cardesin Alejandro , Duxbury Tom , Forget Francois , Giuranna Marco , González-Galindo Francisco , Holmström Mats , Jaumann Ralf , Määttänen Anni , Martin Patrick , Montmessin Franck , Orosei Roberto , Pätzold Martin , Plaut Jeffrey ,   Mex Sgs Team
Published: October 2020

After 16 years in orbit Mars Express remains one of ESA’s most scientifically productive Solar System missions which publication record now approaches 1300 papers. Characterization of the geological processes on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent studies suggest geological evidence of a planet-wide groundwater system on Mars and surface clay formation during short-term warmer and wetter conditions on a largely cold ancient Mars. HRSC team released the Digital Elevation Model (DEM) of the MC-11 quadrangle and the Southern polar cap at 50 m/px resolution. Mars Express provided essential contribution to the selection of the Mars-2020 landing sites and supporting characterization of potential landing sites for Chinese Tianwen-1 mission.One-and-one-half decade of monitoring of atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO2 clouds distribution, collected by SPICAM, PFS, OMEGA, HRSC and VMC together with subsequent modeling have provided key contributions to our understanding of the Martian climate. In 2019 PFS confirmed observations of a methane abundance “spike” in the Gale crater observed in situ by the Curiosity Rover. Recent similar quasi-simultaneous observations were in disagreement, thus indicating that the methane “enigma” continues. This poses a significant challenge to both observers and modelers. The radio-science experiment MaRS revealed fine structure of the boundary layer which depth varies from 2 km in topographic lows to ~10 km over highlands.Observations of the ion escape during a complete solar cycle revealed that ion escape can be responsible for removal of about 10 mbar of the atmosphere over Mars’ history. This implies existence of other, more effective, escape channels. The structure of the ionosphere derived from MARSIS and MaRS sounding was found to be significantly affected by the solar activity, dust loading in the lower atmosphere, and crustal magnetic field. The observations suggest that the sunlit ionosphere over the regions with strong crustal fields is denser and extends to higher altitudes as compared to the regions with no crustal anomalies. Ionospheric models aim at creating user-friendly data base of plasma parameters that would be of great service to the planetary community. Focused exploration of the Martian moons continues.The mission is notionally extended till the end of 2022. A science case for the mission extension till the end of 2025 has been submitted. The talk will give the Mars Express status, review the recent science highlights, and outline future plans including synergistic science with TGO.
Relativistic electron acceleration at Saturn and Jupiter by global scale electric fields
Authors: Roussos Elias , Hao Yixin , Sun Yixin , Liu Ying , Kollmann Peter , Yuan Chongjing , Krupp Norbert , Paranicas Christopher , Zhou Xu-Zhi , Murakami Go , Kita Hajime , Zong Quigang
Published: October 2020

Electrons in Saturn's radiation belts are distributed along discrete energy bands, a feature often attributed to the energisation of charged particles following their rapid injection towards a planet's inner magnetosphere. However, the mechanism that could deliver electrons deep into Saturn's radiation belts remains elusive, as for instance, the efficiency of magnetospheric interchange injections drops rapidly for electrons above 100 keV and at low L-shells. Using Cassini measurements and simulations we demonstrate that the banding derives from slow radial plasma flows associated to a persistent convection pattern in Saturn's magnetosphere (noon to midnight electric field), making the need for rapid injections obsolete. This transport mode impacts electron acceleration throughout most the planet's radiation belts and at quasi and fully relativistic energies, suggesting that this global scale electric field is ultimately responsible for the bulk of the highest energy electrons near the planet. We also present evidence from Galileo and Juno that the influence of Jupiter's inner magnetospheric convection pattern on its radiation belts is fundamentally similar to Saturn's but affects its higher energy ultra-relativistic electrons. The comparison of the two radiation belts indicates there is an energy range above which there is a transition from interchange to global scale electric field driven electron acceleration. This transiroty energy range can be scaled by the two planets' magnetic moment and strength of corotation, allowing us to study these two systems in complement.
Small Mars Mission Architectural Study
Authors: Parfitt Claire , McSweeney Adam , Ball Andrew , De Backer Lisa , Orgel Csilla , Vijendran Sanjay
Published: October 2020

ESA’s current Mars exploration programme consists of the flying orbiters Mars Express and the Exomars TGO, while the Exomars rover is planned for launch in 2022. The Nov 2019 ESA Council of Ministers meeting, Space19+, has approved ESA contributions to a Mars Sample Return Campaign, led by NASA, with a launch of the sample retrieval missions planned to occur as early as 2026.While the vast majority of ESA’s funding for Mars exploration in 2020’s is planned to be invested in Mars Sample Return, there is interest to assess, at Phase 0-level, the possibility of implementing a small mission to Mars in parallel with or soon after the completion of the MSR programme, in order to further the exploration of Mars in areas not directly addressed by MSR.A study was undertaken in the Concurrent Design Facility at ESA, ESTEC in order to assess low cost mission architectures for small satellite missions to Mars. Given strict programmatic constraints, the focus of the study was on a low cost, short mission development schedule with a cost-driven spacecraft design and mission architecture.Three mission cases were studied:The study assessed a wide range of mission architectures and focused on commercial rideshare options to GTO from which the satellite(s) would transfer to Mars utilising either chemical or electric propulsion. The study results showing the feasibility of such missions meeting the programmatic constraints and options for future work will be presented.
Analysis of solar events with Mars Express radio occultation data
Authors: Karatekin Özgür , Krishnan Ananya , Drevon Julien , El Fadhel Ahmed , Bergeot Nicolas , Hinson David , Witasse Olivier
Published: October 2020

ESA’s Mars Exress spacecraft has been exploring the red planet since January 2004. The spacecraft is able to receive and transmit signals at both S-band and X-band. Changes in the radio signals properties while propagating through the atmosphere yield information on the electron density profile. The Mars’ ionosphere is very variable in time. One source of its variability is the solar activity. Here we study the effect of solar flares and coronal mass ejections on the Mars’ ionosphere using the publicly available Mars Express radio occultation data. A new software in python was developed to process the residual frequencies data sets, and was validated using higher-level archival data. We calculate the electron density profiles before, during, and after such solar events. The variations in ionospheric parameters (total electron content, peak density and altitude) are quantified in order to understand the ionospheric changes due to solar activity. As expected, significant variations in these parameters have been identified. The results are compared with additional measurements and models.  Figure 1: The snapshots of the solar wind disturbances on 9 June  2011 (left).  Electron density profiles observed by  MEX  (Right)
Lower atmosphere water/hydrogen activity during the MY 34 regional dust storm
Authors: Holmes James A. , Lewis Stephen R. , Patel Manish R. , Aoki Shohei , Fedorova Anna A. , Chaffin Michael S. , Schneider Nicholas M. , Kass David M. , Vandaele Ann C.
Published: October 2020

Our understanding of the evolution of water on Mars can be advanced through the provision of bounded constraints on the rates of water loss. To understand observed variations in the loss rate, the processes via which hydrogen escapes the martian atmosphere and coupling to the lower atmosphere water cycle also need to be explored. During the Mars Year (MY) 34 regional dust storm that occurred from LS = 320.6-336.5°, an increase in the Lyman alpha brightness (a proxy for hydrogen escape) was observed by the Mars Atmosphere and Volatile EvolutioN Imaging Ultraviolet Spectrograph (MAVEN/IUVS) instrument.  Vertical profiles of water vapour can be retrieved from the Nadir and Occultation for MArs Discovery (NOMAD) and Atmospheric Chemistry Suite (ACS) instruments on the ExoMars Trace Gas Orbiter (TGO). Retrievals could not be made, however, at the time of peak activity observed by MAVEN/IUVS, during the MY 34 regional dust storm. 

We investigate the global distribution of lower atmosphere water using data assimilation covering the time period leading up to and during the MY 34 regional dust storm. The data includes observations of water vapour from NOMAD/ACS (that constrain the initial global distribution of water), temperature profiles from ACS and the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter spacecraft, and dust column from MCS, which are combined with the Open University modelling group Mars Global Circulation model. During the time period of the MY 34 regional dust storm unobserved by ExoMars TGO we can still constrain the simulation using MCS temperature and dust column retrievals, a powerful advantage of multi-spacecraft data assimilation. This method provides the most realistic simulation possible of the chemical and dynamical structure of the lower atmosphere during the observed peak in MAVEN/IUVS observations.  

We identify peak abundance of water vapour and hydrogen at altitudes above 70 km that are consistent with the peak emission observed by MAVEN/IUVS. Spatial variations in elevated water/hydrogen across the globe are linked to the underlying circulation patterns during the MY 34 regional dust storm. 
A two-spacecraft study of Mars induced magnetosphere's response to upstream conditions
Authors: Stergiopoulou Katerina , Edberg Niklas , Andrews David , Sánchez-Cano Beatriz
Published: October 2020

We investigate the effects of the upstream solar wind magnetic field on the Martian induced magnetosphere. This is a two-spacecraft study, for which we use Mars Express (MEX) magnetic field magnitude data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument and Interplanetary Magnetic Field (IMF) measurements and solar wind density and velocity from the magnetometer (MAG) and the Solar Wind Ion Analyzer (SWIA) on board Mars Atmosphere and Volatile EvolutioN (MAVEN), from November 2014 to November 2018. Equally temporally spaced echoes appear in MARSIS' ionograms from which the electron cyclotron frequency and eventually the magnitude of the local magnetic field can be calculated. At the same time solar wind magnetic field data and solar wind parameters from MAG and SWIA respectively are utilized, providing the solar wind input to the Martian system. We make real time comparisons of the IMF and the induced magnetic field in the environment of Mars and we test the ratio B(MEX) /B(MAVEN)  against various parameters such as the solar wind dynamic pressure, velocity, density, Mach number as well as the Martian seasons, latitudes and heliocentric distances. Additionally, we search for disturbances in IMF which then can be traced in the induced field ultimately revealing the response time of the induced magnetosphere to the solar wind behaviour. MEX and MAVEN measurements combined allow us to investigate the response of the Martian induced magnetosphere to the solar wind magnetic field. Real time comparisons of the IMF and the induced field could help us understand the mechanisms controlling the structure of the Martian induced magnetosphere. 
The external and internal magnetic fields of Titan: Cassini observations
Authors: Wei Hanying , Russell Christopher , Ma Yingjuan , Dougherty Michele
Published: October 2020

Titan has a thick atmosphere, the top of which is ionized and interacts with its plasma environment, i.e. usually the Saturnian magnetospheric plasma, but occasionally the magnetosheath or even the solar wind plasma. When the upstream plasma flow encounters Titan, the plasma slows down and diverts around Titan, and the magnetic field slowly diffuses into Titan’s ionosphere and induces currents in the ionosphere. The resulting magnetic field pattern is that, in the upstream of Titan, field lines drape around it, and in the downstream, the field lines stretch tail-like. Gradually these external fields penetrate into the lower atmosphere and the interior of Titan, and induce currents in any conductive layer if a conductive layer does indeed exist in Titan’s interior. This internally induced current acts to exclude the penetrated field. Both the internally induced field and the externally induced ionospheric field have strength and orientation variable with certain time scales because they are responses to the penetrated external field. The Cassini observations are a sum of fields from both internal and external sources. In this paper, we review the low altitude observations from all Cassini Titan flybys and examine the different behaviors of the external and internal fields, which ultimately provide an upper limit to Titan’s internal field leading to indications for Titan’s interior.
Density spikes in Titan’s upper ionosphere
Authors: Edberg Niklas , Wahlund Jan-Erik , Vigren Erik
Published: October 2020

Titan, the largest moon of Saturn, has a dense and nitrogen-rich atmosphere, which is similar to that of early Earth before lived evolved. Solar EUV radiation and energetic particles ionizes the atmosphere and thereby forming a layer of plasma, the ionosphere, in the uppermost part of the atmosphere. The Cassini spacecraft flew past the moon Titan 127 times during its 14-year mission in the Saturn system. During most of these close flybys Cassini entered the ionosphere and some reached the ionospheric peak, located at some 1400 km above the moon surface. With the Langmuir probe instrument, we could study the plasma properties, e.g. ion and electron density, temperature etc., and a very dynamic ionospheric structure was found. In particular, significant and apparently sporadic density spikes in the upper ionosphere were found. These density peaks are manifested as a sudden increase in the measured density by some 10-100 cm-3 over a time period of roughly minutes. These have so far been left unattended in our studies of Titan. We will present some statistics on their appearance and initial result on the mechanism forming them.  
Cooling of Electrons in a Weakly Outgassing Comet
Authors: Stephenson Peter , Galand Marina , Deca Jan , Henri Pierre , Carnielli Gianluca
Published: October 2020

The plasma instruments, Mutual Impedance Probe (MIP) and Langmuir Probe (LAP), part of the Rosetta Plasma Consortium (RPC), onboard the Rosetta mission to comet 67P revealed a population of cold electrons (
BepiColombo – Status and first Results from Activities during Cruise
Authors: Benkhoff Johannes , Murakami Go , Zender Joe
Published: October 2020

BepiColombo was launched on 20 October 2018 the BepiColombo from the European spaceport in French Guyana and is now on route to Mercury to unveil Mercury’s secrets. BepiColombo with its state of the art and very comprehensive payload will perform measurements to increase our knowledge on the fundamental questions about Mercury’s evolution, composition, interior, magnetosphere, and exosphere. BepiColombo is a joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) and consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). The BepiColombo spacecraft is during its 7-year long journey to the innermost terrestrial planet in a so-called ‘stacked’ configuration: The Mio and the MPO are connected to each other, and stacked on-top of the Mercury Transfer Module (MTM). Only in late 2025, the ‘stack’ configuration is abandoned and the individual elements spacecraft are brought in to their final Mercury orbit: 480x1500km for MPO, and 590x11640km for Mio. The foreseen orbits of the MPO and Mio will allow close encounters of the two spacecraft throughout the mission. The mission has been named in honor of Giuseppe (Bepi) Colombo (1920–1984), who was a brilliant Italian mathematician, who made many significant contributions to planetary research and celestial mechanics.On its way BepiColombo has several opportunities for scientific observations - during the cruise into the inner solar system and during nine flybys (one at Earth, two at Venus and six at Mercury). However, since the spacecraft is in a stacked configuration during the flybys only some of the   instruments on both spacecraft will perform scientific observations. In April 2020 BepiColombo has passed Earth. The next planetary flyby will be on 15th October 2020 at Venus.A status of the mission and instruments and a summary of first results from measurements taken during the Earth flyby and during the first two years in cruise will be given. 
Meteor detection from space with Mini-EUSO telescope
Authors: Barghini Dario , Battisti Matteo , Belov Alexander , Bertaina Mario Edoardo , Bisconti Francesca , Capel Francesca , Casolino Marco , Ebisuzaki Toshikazu , Gardiol Daniele , Klimov Pavel , Marcelli Laura , Miyamoto Hiroko , Picozza Piergiorgio , Piotrowski Lech Wiktor , Prévot Guillaume , Reali Enzo , Sakaki Naoto , Takizawa Yoshiyuki ,   Mini-EUSO collaboration
Published: October 2020

Mini-EUSO is a very wide (44°x44°) field of view telescope installed on August 2019 inside the Zvezda Module of the ISS, looking nadir through a UV transparent window and taking data since October 2019. Its optical system consists of two Fresnel lenses, focusing the light onto an array of 36 multi-anode photomultiplier tubes. The focal surface counts a total of 2304 pixels, each one having a footprint of about 6.5 km on ground. The instrument triggers on two different timescales, respectively 2.5 μs (D1) and 320 μs (D2), and perform a continuous monitoring of the UV emission at a 40.96 ms timescale (D3). At time of writing, about one thousand meteors on D3 data have been classified as meteors using our current detection algorithm. We describe here a concept of an alternative algorithm to recognize meteors in the D3 continuous data-stream, which can be also implemented in the future for online triggering, and show some examples of detected meteors by our instrument. We also performed a search of possible coincident detections of Mini-EUSO meteors by ground meteor and fireball networks, such as PRISMA in Italy, to gain a stereoscopic vision of the event itself. In light of these initial results, we present here the capabilities of Mini-EUSO instrument in meteor science.
Enrichment of the HR 8799 planets by minor bodies and dust
Authors: Frantseva Kateryna , Mueller Michael , Pokorný Petr , van der Tak Floris F. S. , ten Kate Inge Loes
Published: October 2020

Are minor bodies and dust delivering volatile and/or refractory materials in exoplanetary systems? Around ~20% of the nearest stars are found to host analogues of the main asteroid belt and the Kuiper belt. Our aim is to study the possibility of material delivery through minor bodies and dust to the planetary surfaces. To shed light on these delivery processes we extrapolate our Solar System scenarios to the exoplanetary system HR 8799. The system is known to host four giant planets and two belts of minor bodies.We performed a set of N-body simulations to study the impact rates of minor bodies and dust on the HR 8799 planets. We find that the planets suffer impacts by objects from the inner and outer belt. We convert these to volatile and refractory delivery rates using our best estimates of the total mass contained in the belts and their volatile/refractory content. Over their lifetime, the four giant planets receive between 10-4 and 10-3 MEarth of material from both belts. This delivery leads to volatile and refractory enrichment of the planets that may be observable. Since the four giants HR 8799 e, d, c, b are located beyond the snow line (and presumably formed there), we expect them to be born volatile-rich. Therefore any future detection of refractories might imply delivery through impacts.
Rotation properties in the Hilda and Main-Belt asteroid families observed by K2 and TESS
Authors: Szabo Gyula , Kiss Csaba , Szakáts Róbert , Pál András , Molnár László , Sárneczky Krisztián , Vinkó József , Szabó Róbert , Marton Gábor , Kiss László
Published: October 2020

We identified 125 individual light curves of Hilda asteroids observed by the K2 mission. We found that despite of the mixed taxonomies, the Hilda group highly resembles the Trojans in the distribution of rotation periods and amplitudes, and even the LR group (mostly C- and X-type) Hildas follow this rule. Contrary to the Main Belt, the Hilda group lacks the very fast rotators. The ratio of extremely slow rotators (P > 100 hr) is a surprising 18%, which is unique in the solar system. The occurrence rate of asteroids with multiple periods (4%) and asteroids with three maxima in the light curves (5%) can be signs of a high rate of binarity, which we can estimate as 25% within the Hilda group. Based on our extraction of 10 thousand full asteroid light curves from the first year observations by TESS (P\'al et al. 2020) we can compare the distribution of rotation period and shape asphericity in the most populated asteroid families overall in the Main Belt. We reveal internal structure of some asteroid families in respect to rotation statistics and signs of rotation properties evolving with age.
Challenges in searching for hydrocarbons in CRISM-IR data
Authors: Manzari Paola , Marzo Cosimo , Ammannito Eleonora
Published: October 2020

After having observed  some absorptions around 3.3 μm band in some CRISM spectra, we begun a study in the range between 3.2 and 3.4 μm to exploit the high spatial resolution of CRISM spectrometer (~18 m/pixel) to look for methane or other C-H absorptions on Mars surface. Concerning methane, we were searching for high concentrations, comparable to the “methane spikes” concentrations detected by Curiosity on Mars surface and the methane plumes detected in Mars atmosphere from ground telescopes. The search for absorptions around 3.3 μm was carried out fitting the spectra of selected CRISM datasets with the MGM function in the 3.2-3.4 μm range.  From the MGM fit we obtained a map of the absorption depths. By this depth map, aside rare, suspected, absorptions, a spectral artifact was highlighted.  Therefore, we chose to consider spectra with absorptions around 3.3 μm not clearly related to known and unknown artifacts, and band depth values greater than 4*standard deviation of the depth map. We used the Planetary Spectrum Generator tool to find the relation between the absorption depths at 3.3 μm and methane concentration. We finally discuss the rare interesting spectra both as potentially true absorptions and as a still unknown artifact.
Dynamics of Titan's high-pressure ice layer
Authors: Kalousova Klara , Sotin Christophe
Published: October 2020

AbstractThe abundance of methane and 40Ar in Titan's atmosphere points to the exchange processes between the surface and the deep interior. Here, we study heat and water transport through Titan's high-pressure (HP) ice layer using a two-phase model of solid ice-liquid water mixture. Our results show that melting may occur at the interface with silicates and that the generated liquids then ascend through the layer before reaching the ocean. This process may facilitate the transport of volatiles from the core to the ocean. We also derive scaling laws to determine the occurrence of bottom melting. Using Cassini data and reasonable values of viscosity and heat flux, we predict that exchange processes through Titan's HP ice layer might be ongoing.IntroductionTitan is likely differentiated into a hydrated silicates core [4] and a hydrosphere composed of a high-pressure (HP) ice layer, an ocean, and an ice I crust. The presence of an ocean was suggested based on the interpretation of (i) measurements of Schumann-like resonance [3], (ii) Cassini-inferred large value of k2 [5], and (iii) the large measured value of obliquity [2].Several observations and their interpretations also point to exchange processes between the deep interior and the atmosphere, such as the large amount of 40Ar [9] and methane [1] and the observed 15N/14N isotope ratio [8]. Here, we study the dynamics of Titan's HP ice layer to investigate its permeability for volatiles transport between the silicate core and the ocean.Numerical modelWe solve the two-phase mixture equations [10] for the mixture of two coexisting phases - solid ice and liquid water. In this approach, the amount of water is described by porosity φ that is defined as a volume fraction of water in the mixture. We use the open source Finite Element Method library FEniCS [7]. For more details, see [6].ResultsFigure 1 shows the difference of temperature T from the melting temperature Tm (top) and the corresponding porosity φ (bottom) for the reference simulation. We observe that: (i) a layer of temperate ice (T=Tm, dark red) is established at the ocean interface, (ii) melt appears in the upwelling plumes and the top temperate layer from where it is extracted into the ocean, (iii) some melt may also be generated at the silicates interface, (iv) the amount of liquid water (porosity) is small (≤ few percent). Being less dense than the HP ice, the generated water provides additional buoyancy that promotes the ascent of hot temperate plumes and the extraction of most of the water produced at the silicates interface. The main model parameters (HP ice layer thickness H, HP ice viscosity μ, incoming silicates heat flux qs) determine the convection and melt generation pattern.The occurrence of melt at the silicates interface is determined by the efficiency of HP ice convection which is characterized by the Rayleigh number. To describe the thermal state of this interface when there is no melt (T
Automatic detection of magnetopause and bow shock crossing signatures in MESSENGER magnetometer data
Authors: Lavrukhin Alexander , Parunakian David , Nevskiy Dmitry , Amerstorfer Ute , Windisch Andreas , Julka Sahib , Möstl Christian , Reiss Martin , Bailey Rachel
Published: October 2020

The magnetosphere of Mercury is rather small and highly dynamic, due to its weak internal magnetic field and its close proximity to the Sun. The changing solar wind conditions principally determine the locations of both the Hermean bow shock and magnetopause. In 2011 – 2015 MESSENGER spacecraft completed more than 4000 orbits around Mercury, thus giving a data of more than 8000 crossings of bow shock and magnetopause of the planet. This makes it possible to study in detail the bow shock, the magnetopause and the magnetosheath structures.In this work, we determine crossings of the bow shock and the magnetopause of Mercury by applying machine learning methods to the MESSENGER magnetometer data. We try to identify the crossings for the complete orbital mission and model the average three-dimensional shape of these boundaries depending on the external interplanetary magnetic field (IMF). Further, we try to clarify the dependence of the two boundary locations on the heliocentric distance of Mercury and on the solar activity cycle phase. Also, we study the effect of the IMF partial penetration into the Hermean magnetosphere. The results are compared with the obtained previously in other works.This work may be of interest for future Mercury research related to the BepiColombo spacecraft mission, which will enter the orbit around the planet at December 2025.
Classifying Exoplanets with Machine Learning
Authors: Barboza Ana , Ulmer-Moll Solène , Faria João
Published: October 2020

More than 4200 exoplanets have been detected and their diversity is remarkable, ranging from very small rocky planets, topuffed gas giants. Several of their types are unknown in our Solar System, hence new classes have been defined to understand thisdiversity and the similarities within each group, such as their formation mechanism or core composition.We aimed to determine the main types of exoplanets, develop a method that automatically associates exoplanets to their type,classifying them into labels with a machine learning algorithm. We also worked to further understand each group, analysing theircharacteristics, and exploring correlations within each group.Given the planetary mass and orbital period of a large number of exoplanets, we used a K-Means clustering algorithm to classify three large groups: Hot Jupiters, Long Period Giants and Small Planets. In order to take into account more planetary and stellar parameters, we also work with the Uniform Manifold Approximation and Projection (UMAP) technique to visualizedata on a 2D map, aiming to find structures within the high dimensional parameter space. We identified different clusters ofexoplanets on this map with the help of groups already described in the literature. We explored how different sets of input parametersimpact the clustering of exoplanets and studied, in particular, the effect of stellar metallicity.We were able to identify 5 different groups: Hot Jupiters, Longer Period Giants, sub-Jupiters, sub-Neptunes and Rocky Planets.We described these groups in terms of values for each parameter, and discussed outliers. We also analysed metallicity separately and verifiedthat, on average, giant planets orbit around higher metallicity stars than non giant planets.The well known groups of giant exoplanets, such as Hot Jupiters and Longer Period giants, are clearly identified in theresulting UMAP 2D parameter space. For smaller planets, several groups were also visible but less separated. We also verified that the global structure is preserved, noticing, for example, the smaller planets (< 8R⨁) are grouped together and well separated from the Hot Jupiters. Adding more samplesof well characterized small planets would certainly help their classification.
Characterising the Hot Jupiters WASP-127\,b, WASP-79\,b and WASP-62\,b with HST
Authors: Skaf Nour
Published: October 2020

We would like to present the atmospheric characterisation of three large, gaseous planets: WASP-127b, WASP-79b and WASP-62b. We analysed spectroscopic data obtained with the G141 grism (1.088 - 1.68 um) of the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127b, which is the least dense planet discovered so far and is located in the short-period Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H$_2$O) = -2.71$^{+0.78}_{-1.05}$, and absorption compatible with an iron hydride abundance of log(FeH)=$-5.25^{+0.88}_{-1.10}$, with an extended cloudy atmosphere.We also detected water vapour in the atmospheres of WASP-79b and WASP-62b, with best-fit models indicating the presence of iron hydride, too.We used the Atmospheric Detectability Index (ADI) as well as Bayesian log evidence to quantify the strength of the detection and compared our results to the hot Jupiter population study by Tsiaras et al 2018.While all the planets studied here are suitable targets for characterisation with upcoming facilities such as the James Webb Space Telescope (JWST) and Ariel, WASP-127b is of particular interest due to its low density, and a thorough atmospheric study would develop our understanding of planet formation and migration. 
Momentum transfer from oblique impacts
Authors: Raducan Sabina D. , Davison Thomas M. , Collins Gareth S.
Published: October 2020

Introduction:Earth is continuously impacted by space debris and small asteroids, and, while large asteroid impacts are very rare, they have the potential to cause severe damage. NASA's Double Asteroid Redirection Test (DART) aims to be the first mission to test a controlled deflection of a Near-Earth binary asteroid [1, 2], by impacting the smaller component of the 65803 Didymos asteroid system, Dimorphos. The impact will thereby alter the binary orbit period by an amount detectable from Earth [3].ESA's Hera mission [3, 4], that will arrive at Dimorphos several years after the DART impact. It will rendezvous with the asteroid system and perform detailed characterisation of Dimorphos's volume and surface properties, as well as measure the DART impact outcome, such as change in the binary system orbit and the volume and morphology of the DART impact crater.In high velocity impacts on an asteroid the change in momentum of the asteroid ΔP can be amplified by the momentum of crater ejecta that exceeds the escape velocity, which is often expressed in terms of the parameter β=ΔP/mU, where mU is the impactor momentum [5]. The amount by which crater ejecta enhances asteroid deflection-that is, the normalised momentum of the crater ejecta that escapes the gravitational attraction of the target body (β-1)-has been found to vary significantly depending on the target asteroid's properties and composition [6].Previous numerical simulations [7, 8] have quantified the sensitivity of the asteroid deflection to target material properties. To allow for a large variety of material properties to be studied, these simulations employed a two-dimensional shock physics code with an axially-symmetric mesh geometry, which restricted the studies to vertical impacts only. However the DART spacecraft will impact the surface of Didymoon at an oblique angle [3]. Here we investigate the influence of impact angle on the ejecta momentum transfer with the aim of developing an empirical scaling relationship for β as a function of impact angle.Numerical methods:We used the iSALE3D shock physics code [9] to numerically simulate the DART impact in two and three dimensions. The DART spacecraft structure was modelled as a porous aluminium sphere, impacting a 20% porous, homogeneous basaltic regolith target at 7 km/s. The cohesive strength of the damaged material was 10 kPa.Influence of the impact angle on the net momentum:Consistent with previous laboratory-scale oblique impact experiments [10, 11] and DART impact models [12], our simulations show that the ejecta from oblique impacts displays higher speeds and lower ejection angles in the downrange direction, and lower speeds and higher ejection angles in the uprange direction of the impact.Figure 1 compares the surface topography of a vertical DART impact, at a 90o angle of incidence to the target plane, and an oblique DART impact at a 45o angle. The time-frames of the oblique impact Figure 1b show a highly asymmetric ejecta distribution at early times of the cratering process
Spectrosopy of interstellar comet 2I/Borisov with VLT X-Shooter
Authors: Guzik Piotr , Drahus Michał
Published: October 2020

AbstractDuring the journey through the solar system, interstellar comet 2I/Borisov has been observed spectroscopically by most of the largest telescopes on Earth, enabling comparative studies of its chemical composition versus solar system comets. Already a few weeks after the discovery, the detection of the CN (0-0 band) in the coma has been reported [1]. Subsequent detections of C2 suggested a significant depletion of this molecule [2,3], however, later evolution of C2 placed it close to the typical values [4]. Pre-discovery images of 2I/Borisov showing this object to be active when far away from the sun indicated that its activity is driven by low-temperature volatiles, later confirmed by the detection of a high abundance of CO [5,6]. High abundance was also reported for NH2 [4]. The water production rates derived from the detection of [OI] 6300 A line [7] were consistent with SWIFT/UVOT observations [8].Here we report our spectroscopic observations of 2I/Borisov from VLT X-Shooter. We collected over 10 hours of data on UT 2020 January 28th, 30th, and 31st obtaining the deep spectrum of this object taken around the time of its maximum brightness. The spectrum covers an unprecedented wavelength range of 300 - 2500 nm that comprises numerous characteristic cometary emissions. The excellent sensitivity of the spectrum, combined with the decent spectral resolution provided by X-Shooter over the entire, enormous wavelength range makes the collected material unique.AcknowledgementsAuthors are grateful for support from the National Science Centre of Poland through SONATA BIS grant number 2016/22/E/ST9/00109 to M.D. References[1] Fitzsimmons, A., Hainaut, O., Meech, K. et al.: Detection of CN Gas in Interstellar Object 2I/Borisov, ApJL, Vol. 885, L9, (2019)[2] Kareta, T., Andrews, J., Noonan, J. et al.: Carbon Chain Depletion of 2I/Borisov, ApJL, Vol. 889, L38, (2020)[3] Lin, H., Lee, C., Gerdes, D. et al.: Detection of Diatomic Carbon in 2I/Borisov, ApJL, Vol. 889, L30, (2020)[4] Bannister, M., Opitom, C., Fitzsimmons, A. et al.: Interstellar comet 2I/Borisov as seen by MUSE: C2, NH2 and red CN detections, https://arxiv.org/abs/2001.11605, (2020)[5] Bodewits, D., Noonan, J., Feldman, P. et al.: The carbon monoxide-rich interstellar comet 2I/Borisov, NatAst, (in press)[6] Cordiner, M., Milam, S., Biver, N. et al.: Unusually high CO abundance of the first active interstellar comet, NatAst, (in press)[7] McKay, A., Cochran, A., Dello Russo, N. et al.: Detection of a Water Tracer in Interstellar Comet 2I/Borisov, ApJL, Vol. 889, L10, (2020)[8] Xing, Z., Bodewits, D, Noonan, J. et al.: Water Production Rates and Activity of Interstellar Comet 2I/Borisov, ApJL, Vol. 893, L48, (2020)
Planetary inertial modes and their relation to nutations
Authors: Rekier Jérémy , Triana Santiago , Trinh Antony , Dehant Véronique
Published: October 2020

Inertial modes are global oscillations that take place inside rotating objects, such as stars and planets with a fluid core and/or liquid ocean, which result from the restoring effect of the Coriolis force. Experimental studies in laboratory have shown that these modes can be excited by the action of tidal deformation at the fluid boundary as well as precession of the rotation axis. However, the influence of inertial modes on the rotation of planets remains unclear. As these modes have frequencies contained within the band -2
Machine Learning Applications to Kronian Magnetospheric Reconnection Classification
Authors: Garton Tadhg , Jackman Caitriona , Smith Andrew , Yeakel Kiley , Maloney Shane
Published: October 2020

Signatures of magnetic reconnection in Saturn's magnetotail are identified in magnetometer observations by characteristic deviations in the northward component of the magnetic field. These magnetic deflections are caused by travelling plasma structures created by reconnection rapidly passing over the observing spacecraft. The identification of these reconnection signatures has long been performed by eye, and more recently through semi-automated methods, however these methods are often limited through a required human verification step. Here, we present a fully automated, supervised learning machine learning (ML) model to identify evidence of reconnection in Cassini MAG (magnetometer) observations of the Kronian magnetosphere, constructed using the Smith et al, 2016. reconnection catalogue which contains hundreds of examples of plasmoids, travelling compression regions and dipolarizations. This ML model is capable of rapidly identifying reconnection events in large time-span Cassini datasets, tested against the full year of 2010 with a high level of accuracy (99\%), true skill score (0.97), and Heidke skill score (0.85). From this ML model, a full cataloguing and examination of magnetic reconnection in the Kronian magnetosphere across Cassini's near Saturn lifetime is now possible.
Slow rotators and binary candidates among the Jovian Trojans with K2
Authors: Kalup Csilla , Molnár László , Kiss Csaba , Szabó Gyula M. , Pál András
Published: October 2020

The Kepler space telescope collected continuous photometry of several Jovian Trojan asteroids in the Solar System during its K2 mission. We extracted light curves 43 new targets from K2 Campaigns 11-19 using our own photometric package developed for moving objects in the Kepler images which, together with the 56 asteroids from Campaign 6, brings the total sample size up to 99 asteroids. We calculated rotational frequencies and amplitudes for each object and their distributions, and we derived statistics on the binary fraction and possible compositions of these asteroids. We find and excess of very slow rotators (>100 hours) and a possible dichotomy in the period distribution. When compared to other space-based photometric results, we find that the distribution of Hilda rotation periods detected with K2 shows the same possible dichotomy, but the large sample of main-belt asteroids measured with the TESS space telescope does not. The excess of slow rotators corroborates with an outward origin, with synchronized binaries migrating inwareds from the Kuiper belt, and some of them dissociating along the way, creating very slowly rotating single objects. Both a low critical density limit and comparison with strengthless ellipsoid models indicate that none of the objects exceed the density of icy objects, further strengthening an inward migration scenario. We estimate a binary fraction of at least 21% based on the number of high-amplitude, long-period objects, in agreement with earlier results. Large photometric amplitudes are prevalent over the entire period range, and we cannot fit all objects with a strengtless model in rotational equilibrium.We highlight a few individual objects as well. (99306) 2001 SC101 is the only asteroid observed in to Campaigns, from different sides of the Sun, and we find clear differences in the light curve shape. (13062) Podarkes is the principal body of a proposed small family: we detect a rotation period of 245 hr which puts it into the very slow rotator group. Finally, we present the first continuous light curve of (11351) Leucus, one of the targets of the Lucy spacecraft, and confirm that it also rotates exceedingly slowly, with a period of 445 hr.