bluuebunny/crossref_metadata_2025 huggingface dataset:
Our Space Our Future – Space Careers for everyone!
Authors: Almeida Maria Luísa , Doran Rosa
Published: October 2020

Our Space Our Future – Space Careers for everyone!Our Space our Future (OurSpace), an H2020 Project, visions a society that enables and empowers all students, regardless of gender, ethnicity, disability or socio-economic background, to consider a career related to space science as a relevant, attainable and exciting aspiration for their future.The OurSpace project is designing and running sustainable education and outreach activities, and taking these out into communities, ensuring that underserved audiences are embraced and integrated into the project. These actions aim to foster the interest of young students in space-related topics and show them how space impacts their daily life, even though they might not be aware of it. Working closely with teachers and educators, OurSpace helps them develop attractive interdisciplinary activities that raise their interest in STEAM subjects.The project encompasses space science, industry and careers globally, but there is a strong focus on planetary sciences since it is one of the first space topics in primary school and is also easily related to the curriculum later on.There are three main lines of action: school activities, family and community events, and teacher training. Strategies have been outlined by the consortium to make sure we reach students/families/communities that have less opportunities to be exposed to this theme.Schools are being chosen taking into account indicators of disadvantage status such as FSM, geographical isolation, number of immigrants. Activities are planned to be interdisciplinary,  interactive and inquiry-based, such as doing workshops on space subjects with non-science teachers, having students designing missions collaboratively, designing accessible activities for a range of ages and abilities.Events are being prepared to make space relevant to family/community daily life - getting role models from the local school or community,  that challenge gender and other stereotypes; having students co-creating activities with family and community; preparing events that explore space science but does not mention it explicitly.Teachers are the key link to students, families and community, so there is a big emphasis on teacher training. Working closely with teachers, we can support them, prioritize inclusion, co-create inspirational activities, and open a door to the future.Space is a stable growing sector, that provides many career opportunities for young students. However, few young people consider pursuing a career in a space-related field. We want to inspire our students, families and communities, guiding them towards new paths they didn’t know were available.OurSpace will engage over 60,000 people across the programme, with a longitudinal evaluation study that explores improved scientific literacy, interest and confidence in space science themes and assesses the impact on space-related and STEM choices and career aspirations of 5,000 directly-participating students across 4 delivery countries.
Landslides on Comet 67P/Churyumov–Gerasimenko: Stability of Ejecta in Places of their Depositions
Authors: Czechowski Leszek , Kossacki Konrad
Published: October 2020

Introduction: The phenomenon of landslide is a form of the gravity movement. Comets have weak gravity field, so it is believed that probability of landslides is very low. However observations from space missions to comets 9P/Tempe 1 and 67P/Churyumov – Gerasimenko revealed existence of these mass motion.The causes of landslides are usually related to instabilities of slopes. It is often possible to indicate a few causes of the landslide but usually only one factor is considered to be a trigger. Causes are the factors responsible for making the slope unstable in respect to small disturbances. Some causes could also trigger landslides [1].In the present paper we consider comet 67P/Churyumov–Gerasimenko. Investigation of its nucleus indicated existence of deposits typical for landslides. In previous works we consider ejecta from some places of the comets. In presen paper we investigate stability of ejecta in the place of landing.   Slopes of the surface: On the small bodies of spherical shape the area with large slope (in respect to the local gravity) is rather limited. The different situation could be observed on highly asymmetric bodies [2].The gravitational field of 67P/Churyumov–Gerasimenko comet is very complicated. There are several regions of different slopes of the physical surface in respect to the gravity. The most of the surface (~74%) has the slope in the range 0< α
CaRM: Retrieving exoplanets transmission spectra with high resolution spectroscopy
Authors: Cristo Eduardo
Published: October 2020

High resolution spectra is the standard source to derive precise radial velocities. With the development of state-of-art instrumentation, like ESPRESSO, we are able to have higher resolutions and long term stability.During a transit the star light from a observer point of view is filtered in the day-night terminator of the exoplanet. As the light transverses it, diverse chemical species, dust, hazes and clouds let an imprint in the host star light. This allows to detect exoplanet atmospheres using transmission spectroscopy. However, a chromatic approach of the Rossiter-McLaughlin (RM) effect also permits to measure the planet radius wavelength dependence as a composition proxy.The Rossiter-McLaughlin effect is an phenomenon in radial velocities. When a star rotates, there is a velocity distribution created by the half of the surface that is moving towards the observer, presenting a intrinsic blueshift, compensated by the redshifted portion rotating away. A transiting planet produces an asymmetric distortion of the stellar line profiles of an observer giving origin to a RM profile.We present CaRM (Chromatic Rossiter-McLaughlin), a code developed to retrieve the transmission spectrum of an exoplanet using HARPS and ESPRESSO data. It employs a Markov chain Monte Carlo algorithm to fit two distinct RM models, with a linear or quadratic limb-darkening law, to Cross Correlated spectra. The orbital parameters retrieved as result, e.g. spin-orbit misalignment, are of foremost importance when constraining the models of planetary formation and evolution.A chromatic approach to the RM has been used in HD 189733b HARPS transit data, which is reproduced by this code with a good degree of agreement to previous results. We expect now to apply CaRM to ESPRESSO data (ESO-VLT), taking this method to a new level.
Towards a Multi-Decadal Dataset of Auroral Kilometric Radiation (AKR) Source Parameters with Wind/WAVES
Authors: Waters James , Jackman Caitriona , Whiter Daniel , Lamy Laurent , Bonnin Xavier , Cecconi Baptiste , Issautier Karine
Published: October 2020

Auroral Kilometric Radiation (AKR) is radio emission that originates in particle acceleration regions along magnetic field lines that coincide with discrete auroral arcs. Radio astronomy instruments aboard various spacecraft have been used to derive the flux density, source direction and other parameters of emissions of various origin. The Wind spacecraft has been in operation for 25 years and the WAVES radio instrument has previously been considered for a technique to also derive the Stokes parameters of a partially polarised radio source. While previous applications of the technique have seen it modified to study solar radio emissions, further examination is needed for its application to AKR. After correcting appropriately for the characteristics of the AKR emissions, this technique can be used to produce a utile dataset of AKR observations. Statistical properties of AKR can be examined, with the extent of local time sampling of Wind bolstering previous studies. The previously observed correlation between morphological changes in the source region and magnetospheric substorm onset can be studied further, and lists of substorm phase timings can be used to examine the general variability during these events.
Ancient Martian Climate with ROCKE-3D
Authors: Guzewich Scott , Way Michael , Aleinov Igor , Wolf Eric , Del Genio Anthony , Tsigaridis Kostas , Wordsworth Robin
Published: October 2020

AbstractWe present simulations of the ancient Martian climate with the Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) general circulation model.  We evaluate the efficacy of CO2-H2 and CO2-CH4 collision-induced absorption (CIA) in producing temperate conditions on Mars during the late Noachian-early Hesperian period near 3.7 Gya.  We additionally study the fate of liquid water if it was on the surface during that time period in history.Geologic evidence indicates that ancient Mars supported widespread surface liquid water approximately 3.5-4 Ga (e.g., [1], [2]).  For nearly as long, climate modeling has attempted to find a self-consistent mixture of atmospheric gases with realistic atmospheric pressures that could support a hydrological cycle that is consistent with the geologic evidence (see [3] for an overview).  Despite those efforts, substantial doubt remains about the feasibility of a “warm and wet” climate that could have existed for sufficient time to produce the geologic evidence during the period of the faint young Sun. Recently, [4] and [5] (among others) have shown that H2, in combination with CO2 and CH4, can produce efficient CIA that provides substantial warming at plausible surface pressures (i.e.,
Combining Kepler, TESS and ground based data for characterising exoplanets and stellar activity
Authors: Foing Victoria , Heras Ana , Foing Bernard
Published: October 2020

This work compares the information obtained from TESS and Kepler lightcurves, and integrates information obtained from ground based observatories. We apply Machine learning methods for modelling stellar and instrumental systematics in lightcurves because they can quickly identify patterns in data without prior knowledge of the functional form. We use a Gaussian Process to model the stellar activity, background granulation, and transit signals simultaneously because we expect that using a multi-component model can improve planetary characterisation.  This work seeks to address the following questions:RQ1: How accurately can we model the stellar activity and transit signals in TESS and Kepler lightcurves with machine learning?RQ2: To what extent can we use these models to interpret the rotation periods and activity cycles of the stars?RQ3: To what extent can we use these models to detrend the lightcurves and improve transit exoplanet characterization?The model is initialized using information from Box Least Squares, LombScargle analysis, and Autocorrelation functions, and then Markov Chain Monte Carlo algorithms are run to fit rotational modulation parameters and planet parameters.  We compare the results of this method across different missions (TESS and Kepler) and compare the results of this method with results obtained from ground based surveys. We illustrate the comparison and the astrophysical results in the case of WASP62 and Kepler 78 targets. 
Calculating the dust properties of the class I source Elias29
Authors: Koutoulaki Maria , Testi Leonardo , Miotello Anna , Szűcs László , Yamamoto Satoshi , Ceccarelli Cecilia , Chandlder Claire , Codella Claudio , Sakai Nami , collaboration Faust
Published: October 2020

A first step towards understanding planetary formation is the characterisation of the structure and evolution of protoplanetary discs. A variety of planetary systems has been discovered in recent years and it likely depends on the early history of their formation. Thus understanding the chemical composition of early solar-like protostars is crucial. To be able to study the lines in detail though, a good knowledge of the dust properties and in particular the optical depth is needed in order to interpreted the lines correctly.

 

In this talk I want to present our results of the class I source Elias29 as part of the FAUST (fifty au study of the chemistry in the disk/envelope system of solar-like protostars) collaboration. The goal of FAUST is to quantify the chemical composition of the envelope/disk system of solar-lie class 0 and I protostars. With the high spatial resolution of 50 au in band 3 and band 6 ALMA data we can spatially resolve the envelope and the disk on this source and calculate the dust properties of the two components.
Operation of future lunar society in 204
Authors: Imai Shigeru
Published: October 2020

In 2040, a world where 1,000 people stay on the moon all the time and 10,000 people visit every year is imagined and its feasibility and technology roadmap are discussed. In such a world, not only the minimuminfrastructure necessary for residents and travelers to survive such as habitation, transportation, power, communication,  food  and  water, but  also  comfortable  living  and entertainment  are  required.   Also,  in order to make a lunar society sustainable, not only the individual elements such as in-situ use of resources (ISRU) technology and closed circulation system, which are currently being researched and developed all over the world, but it is also important to design architecture and operate the infrastructure and facilities on lunar surface and lunar orbit so that they work together in an organic manner to improve efficiency and optimization as a whole.  In this session, we will present one way of thinking about the comfortable lifestyle for residents in the 2040 lunar society, and the overall operation and management that enables a sustainable lunar society.
Community Access to CHEOPS
Authors: Isaak Kate
Published: October 2020

Launched on 18 December 2019, CHEOPS (CHaracterising ExOPlanet Satellite) is the first exoplanet mission dedicated to the search for transits of exoplanets by means of ultrahigh precision photometry of bright stars already known to host planets. It is the first S-(small) class mission in ESA’s Cosmic Vision 2015-2025, and a partnership between Switzerland and ESA, with important contributions from 10 other member states.CHEOPS will provide the unique capability of determining accurate radii for a subset of planets in the super-Earth to Neptune mass range, for which masses have already been estimated from ground- based spectroscopic surveys. It will also provide precision radii for new planets discovered by ground- and space-based transit surveys, including TESS. By combining known masses with CHEOPS sizes, it will be possible to determine accurate densities for these smaller planets, providing key insight into their composition and internal structure. By identifying transiting exoplanets with high potential for in-depth characterisation – e.g. those that are potentially rocky and have thin atmospheres - CHEOPS will also provide prime targets for future instruments suited to the spectroscopic characterisation of exoplanetary atmospheres.80 % of the obsering time in the 3.5 year nominal mission lifetime on the satellite is dedicated to the Guaranteed Time Observing Programme defined by the CHEOPS Science Team. The remaining 20% is available to the Community through the ESA Guest Observers Programme, which comprises annual calls and a discretionary time component.    In this final poster in a series of three, we provide an overview of Community Access to CHEOPS, with an emphasis on the CHEOPS Guest Observers Programme.
A comprehensive comparative exoplanetology program to probe atmospheric properties of close-in giant exoplanets
Authors: Panwar Vatsal , Désert Jean-Michel , Todorov Kamen , Bean Jacob , Huitson Catherine , Fortney Jonathan , Stevenson Kevin , Bergmann Marcel
Published: October 2020

We present a comparative exoplanetology program of a broad sample of transiting gas giant exoplanet atmospheres using a multi-wavelength ground-based survey. The survey comprises optical and near-infrared spectrophotometric observations with Gemini/GMOS and Keck/MOSFIRE respectively. By observing transits and eclipses of an ensemble of close-in gas giants spanning a range of varying bulk and stellar host properties, and using a consistent methodology for modeling systematics and stellar activity, we put constraints on the presence and properties of clouds, alkali metals, and molecular absorbers in their atmospheres. Combining these results with observations from other observatories (TESS, HST, and Spitzer), we probe the overall properties of close-in giant exoplanet atmospheres, including their metallicity, using multiple tracers across the wide wavelength range. Characterizing the bulk chemical and physical properties of the whole sample helps to constrain the formation and evolution histories of these planets. We also discuss the opportunities of low-resolution spectroscopy observations of exoplanet atmospheres in the JWST era.
Modelling high-resolution transmission spectra of the ultra-hot jupiter wasp-76b with 3D Monte-Carlo radiative transfer
Authors: Wardenier Joost , Parmentier Vivien , Lee Graham
Published: October 2020

Ultra-hot Jupiters are tidally-locked gas giants with two chemical regimes: on the scorching dayside molecular species are dissociated and metals are ionised, while the permanent nightside is cool enough for cloud formation to occur. This means that the abundances of particular chemical species, such as iron, will exhibit a sharp gradient across the terminator region, which can be probed by transmission spectroscopy. We present a state-of-the-art 3D Monte-Carlo radiative transfer framework, adapted from Lee et al. (2017, 2019), that allows for the 3D modelling of high-resolution spectra of ultra-hot Jupiters. We use this tool to post-process the output of the SPARC/MITgcm global circulation model, with the aim to better understand how inhomogeneous chemistry, clouds and Doppler shifts due to atmospheric dynamics impact the appearance of a transit spectrum and its cross-correlation signal.
 
In this talk, we apply our model to the transit of WASP-76b, for which Ehrenreich et al. (2020) recently presented a time-varying iron signature at high spectral resolution. The observation suggests that iron condenses on the nightside of the planet. We show that different parts of the limb lead to very different cross-correlation signals and we show that the relative contributions from the east and west limb change during the transit, resulting in a time-varying cross-correlation signal. Finally, we explore different atmospheric scenarios for WASP-76b and we demonstrate that the occurrence of iron condensation, combined with the specific time-varying geometry during the transit, can quantitatively reproduce the Ehrenreich et al. (2020) result.

 
The Characterizing Exoplanet Satellite (CHEOPS): news and first results
Authors: Lendl Monika
Published: October 2020

The Characterizing Exoplanets Satellite (CHEOPS) is the first ESA space mission dedicated primarily to the study of exoplanetary systems. The satellite, carrying a 30cm photometric telescope, has been launched successfully in December 2019 and has seen first light in January 2020. Throughout it's nominal mission of 3.5 years, it will perform ultra-high precision photometry of bright stars know to host extrasolar planets. Next to searching for transits of planets known from radial velocities and measuring precise radii of known transiting planets, CHEOPS will dedicate approximately 25% of its observing time to characterizing exoplanet atmospheres. In this talk, I will describe the CHEOPS space mission, summarize its scientific program and detail how we will use CHEOPS to probe exoplanet atmospheres, such as optical-light occultations and planetary phase curves. After introducing the mission, I will give an update on it's current status, performances and show first results. I will conclude by discussing synergies with other facilities, both ground- and space-based, and illustrate how together they will advance our global understanding of planetary atmospheres.
Scientific Co-operative Rover with Artificial Intelligence for Futuristic Scientific Experiments on Moon
Authors: Rao Sandhya , Chowdhury Sreemon
Published: October 2020

With recent scientific experiments carried out and results have shown an immense studies inoperation in the complex lunar environment and exploiting the moon base as a scientific platformfor both research and major challenges in exploration. Notion Robotics Lab proposes a highlyadvanced lunar lander to prepare future missions on moon. The scientific areas for investigationon the lunar lander include the radiation environmental and its effect, dust, plasma, the mostimportant being the properties of moon dust and its effect on human intervention. NotionRobotics Lab will propose a payload which interfaces the information and the boundaryconditions. This paper discusses the scientific objectives for the futuristic mission whichemphasizes human robot exploration and builds a prototype scientific payload to be part of themission and also design of scientific instruments.Notion Robotics Lab has developed the sophisticated autonomous co-operative rovers withmultiple intelligence systems to study life on lunar base and capable of handling multipledecisions without human interference. This rover will be built as per the map of the terrains inthe lunar base thus operating different tasks. With advancement of different payloads andscientific instruments the rover may able to map the large tracts of the surface thus do complextasks and experiments. Notion Robotics Lab plans to execute with the partnership withUniversities and Space Agencies thus proposing broader experiments in futuristic lunar mission.Keywords:- Autonomous Co-operative Rover, Artificial Intelligence, Scientific Instruments,Understanding Life, Lunar Lander
The detection of circumbinary exoplanets through gravitational waves astronomy
Authors: Danielski Camilla , Korol Valeria , Tamanini Nicola
Published: October 2020

The discovery and study of exoplanets in their diversity is arguably one of the most exciting development in astronomy over the past 25 years, rivalled by the detection of gravitational waves.In this talk I will merge these two fields presenting an original observational method which employs gravitational waves to detect exoplanets. In particular I will show how the Laser Interferometer Space Antenna (LISA) mission will be able to observe Jupiter-like exoplanets orbiting white dwarfs binaries. This technique will allow us to both overcome the selection bias of current electromagnetic detection techniques, whose observations are limited to the Solar neighbourhood, and to search for post-main sequence exoplanets everywhere within the Milky Way and the Magellanic Clouds. Detections by LISA will deepen our knowledge on the life of exoplanets subsequent to the most extreme evolution phases of their hosts, clarifying whether new phases of planetary formation take place later in the life of the stars. Finally, in the spirit of the new era of multi-messenger astronomy, I will discuss the possibilities that could open for the field of exoplanets when standard electromagnetic techniques work in synergy with gravitational-wave astronomy.
Verification of the V-type asteroids rotation distribution outside Vesta family
Authors: Troianskyi Volodymyr ,   V-type asteroid team
Published: October 2020

The main objective of the study is the verification of the V-type rotation distribution. Though numerical modelling, Nesvorny et al. (2008) showed that asteroids can migrate through Yarkovsky effect and resonaces outside the boundaries of the Vesta family. In particular they found that objects which end up in the scattered resonances region (so-called Cell I, defined by orbital elements 2.2 AU < a < 2.3 AU, 0.05 < e < 0.2, 0 < i deg < 10 deg) typically have retrograde rotation and thermal parameters that maximize the Yarkovsky drift. Consequently, most of the V-types in Cell I should be retrograde rotating. Similarly showed that asteroids migrating to the low inclination region (Cell II defined by 2.32 AU < a < 2.48 AU, 0.05 < e < 0.2, 2 deg < i < 6 deg) should be predominantly rotating prograde (60% of objects).We perform photometric observations and determine spins and shapes of V-type objects in Cell I and II to verify the predicted statistics of sense of rotation. Finding significantly un-matching statistics for rotational properties may strengthen the idea that there may be fragments of other (than Vesta) differentiated planetesimals in the inner main belt. We show preliminary results for the first few asteroids in Cell I and II.
Solar cycle changes in the interplanetary magnetic field variability at Mars
Authors: Durward Sofija , Wild Jim , Lillis Rob
Published: October 2020

As Mars has no intrinsic magnetic field, it is inherently strongly influenced by the solar wind. However, little is known about the scale of variability of the solar wind at this distance from the Sun. The lack of an upstream solar wind monitor at Mars sometimes necessitates assumptions about the variability of solar wind and interplanetary magnetic field (IMF) conditions at Mars, and without a clear understanding of how the solar wind varies at Mars it is difficult to know whether these assumptions are appropriate. We present a study which quantifies the variation of the IMF at Mars during periods near solar maximum and minimum, by comparing magnetometer measurements of the pristine IMF from the Mars Global Surveyor (MGS) mission (between 1997 and 1999) and the MArs Volatile EvolutioN (MAVEN) mission (between 2014 and 2016). This study finds the IMF to be notably steadier in field strength and cone angle direction during the MAVEN mission than the MGS mission (shown in Figures 1 and 2), with little difference in the clock angle variation between the two missions. Additionally, the variability of both the field strength and the clock angle is found to be dependant on the cone angle of the measurements, with periods of IMF oriented close to the orbital plane of Mars being considerably steadier than periods of IMF oriented approximately perpendicular to it. Results from this study suggest that the IMF at Mars is steadier at times near solar maximum than at times near solar minimum, and quantify the error in estimates of IMF parameters hours after measurement. However, using solar 10.7cm flux as a proxy for solar activity, we show that the time for the IMF to decorrelate does not directly depend on the solar activity. Figure 3 shows the decorrelation time and the solar activity for both the MGS and MAVEN datasets. No clear correlation is visible in the graphs, suggesting that the reason for the differences in the IMF variability between the two missions is still unclear.
Breaking spin-orbit measurement degeneracies with precise photometric and spectroscopic transit observations
Authors: Wyttenbach Aurélien
Published: October 2020

Spin-orbit angle measurments (e.g., with the Rossiter-McLaughlin effect) are often degenerates. This is due to fundamental symetries in the problem, to complex correlations between parameters, and to the difficulty to measure some parameters (e.g., the stellar inclination). Recently, independent teams reported spin-orbit angle measurments of the same systems (e.g., KELT-9) using different instruments and methods. In particular, exoplanetary systems around rapidly rotating and pulsating early-type stars present different possibilities to measure their spin-orbit angles. For these systems, one can access the stellar inclination thanks to the independent detections and studies of stellar differential rotations, of stellar gravity darkening, and of stellar pulsations. In this presentation, we will show that these measurments don't necessary have the same symetries. Thus, it may be possible to break degenaracies in the spin-orbit angle measurment by combining precise photometric transit (that allow us to measure, e.g., gravity darkening) and precise spectroscopic transit measurments (that allow us to measure, e.g., differential rotation and pulsations). A tentative coherent explanation of recent data on the KELT-9 system will be presented as an example and as a motivation to develop new synergies in this domain.
Retrieving the atmospheric properties of directly imaged planets
Authors: Mollière Paul ,   ExoGRAVITY team and collaborators
Published: October 2020

Young gas giant planets still glow hot from formation, sometimes even showing signs of active accretion. Studying the atmospheres of these directly imaged planets may help placing constraints on how they formed, which may also shed light on the formation process of the planetary systems they reside in. In general, this may be achieved by connecting atmospheric to planetary composition, and planetary composition to planet formation. In my talk I will present our work that investigates the first step of this process, namely constraining the atmospheric abundances of gas giant exoplanets via free retrievals of GRAVITY, SPHERE and GPI observations. Free retrievals work by parameterizing the atmospheric structure as much as possible when calculating spectra, thereby allowing the data to constrain the atmosphere’s state. This relaxes the need for a model to fulfill given assumptions which may not accurately describe the atmospheric physics, due to modeling uncertainties and oversimplifications. At the same time caution is required because unphysical atmospheric models can potentially lead to excellent fits to spectroscopic observations. I will show why including clouds and scattering is crucial for the analysis of directly imaged planets, what the effects of using inappropriate cloud models are, and outline the next steps to develop this analysis method further.
Sulfuric acid vapor and sulfur dioxide in the atmosphere of Venus as observed by VeRa
Authors: Oschlisniok Janusz , Häusler Bernd , Pätzold Martin , Tellmann Silvia , Bird Michael
Published: October 2020

The main Venus clouds, covering the entire planet between approx. 50 and 70 km altitude, are believed to consist mostly of liquid sulfuric acid. Below the clouds, the temperature is high enough to evaporate those droplets into gaseous sulfuric acid forming a haze layer which extends to altitudes as deep as 35 km. H2SO4(g) is the main absorber of radio waves as was observed in Mariner, Pioneer Venus, Magellan and Venera radio occultation measurements. Radio wave absorption measurements can be used to derive the amount of H2SO4 as well as to estimate upper limits of SO2 in Venus’ atmosphere. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2014 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. Thanks to the orbit of VEX, a wide range of latitudes and local times was covered so that a global picture of the H2SO4(g) ditribution was obtained. We present H2SO4(g) profiles as well as upper limits of sulfur dioxide near the cloud base derived from the X-band radio signal from the entire Venus Express mission. More than 600 H2SO4(g) profiles show the global sulfuric acid vapor distribution covering the northern and southern hemisphere on the day- and night side of the planet. A distinct latitudinal H2SO4(g) and SO2 variation and a southern northern symmetry are clearly visible. Observations over 8 years allow to study also long-term variations. Indications for temporal H2SO4(g) and SO2 variations are found, at least at northern polar latitudes. The results shall be compared with observations retrieved by other experiments onboard Venus Express. Additionally, the observed H2SO4(g) distribution will be compared with results obtained from a mass transport model.
Fatigue-driven boulder exfoliation as a driving mechanism for Bennu’s activity
Authors: Molaro Jamie , Hergenrother Carl , Chesley Steve , Hanna Romy , Haberle Chris , Ballouz Ronald , Schwartz Steve , Bottke William , Walsh Kevin , Campins Humberto , Lauretta Dante
Published: October 2020

Abstract: Thermally driven fracture processes, such as thermal fatigue, have been hypothesized to drive rock breakdown and regolith production on asteroid surfaces [e.g., 1-7]. Thermal cycling induces mechanical stresses in rocks that drive the propagation of microcracks, which may grow into larger-scale features. This can drive the development of morphological signatures such as surface fracturing and disaggregation, and through-going fractures that split boulders apart. The nature and rate of boulder breakdown is controlled by rock composition, as well as the rotation period and solar distance of the body, suggesting its signature varies widely across the diverse asteroid population. Understanding how the process operates is critical to characterizing their surface properties and evolution.Images from the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft of the surface of Bennu provide the opportunity to search for in situ evidence of thermal breakdown over a wide range of scales. Recent works by the authors [7-9] show observations of boulder morphologies consistent with terrestrial observations [e.g., 10] and models of fatigue-driven boulder exfoliation [e.g., 11], i.e., the flaking of thin layers or shells of material from boulder surfaces. Relating these observations to thermally induced stress fields in phyllosilicate boulders reveals that such features develop via the propagation of surface-parallel fractures during periods of day when boulder surfaces are heating. The magnitude of these stress fields ranges from ~0.3 to 3 MPa for boulders up to 6 m in diameter, which is comparable to the tensile strengths of terrestrial phyllosilicate rocks (e.g., serpentinite) and sufficient to drive subcritical crack growth (thermal fatigue). The thickness of resulting exfoliation layers predicted by the model ranges from ~1 mm to 10 cm, which is consistent with terrestrial observations of exfoliation cracks [10] and with the thicknesses of exfoliation layers observed on Bennu’s boulders [9].Further, we explore how boulder exfoliation may lead to the ejection of particles observed at Bennu’s surface [9] in an analogous manner to mobilization of rock fragments during large-scale, terrestrial dome exfoliation events [12]. We have observed particle ejection events from Bennu’s surface repeatedly since first entering orbit in January 2019. Observed particles range in size from
Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H2O, Na, and K
Authors: Welbanks Luis , Madhusudhan Nikku , Allard Nicole F. , Hubeny Ivan , Spiegelman Fernand , Leininger Thierry
Published: October 2020

Atmospheric compositions can provide powerful diagnostics of formation and migration histories of planetary systems. In this talk, I will present the results of our latest survey of atmospheric compositions focused on atmospheric abundances of H2O, Na, and K. We employ a sample of 19 exoplanets spanning from cool mini-Neptunes to hot Jupiters, with equilibrium temperatures between ~300 and 2700 K. We employ the latest transmission spectra, new H2 broadened opacities of Na and K, and homogeneous Bayesian retrievals. We confirm detections of H2O in 14 planets and detections of Na and K in 6 planets each. Among our sample, we find a mass-metallicity trend of increasing H2O abundances with decreasing mass, spanning generally substellar values for gas giants and stellar/superstellar for Neptunes and mini-Neptunes. However, the overall trend in H2O abundances, is significantly lower than the mass-metallicity relation for carbon in the solar system giant planets and similar predictions for exoplanets. On the other hand, the Na and K abundances for the gas giants are stellar or superstellar, consistent with each other, and generally consistent with the solar system metallicity trend. The H2O abundances in hot gas giants are likely due to low oxygen abundances relative to other elements rather than low overall metallicities, and provide new constraints on their formation mechanisms. Our results show that the differing trends in the abundances of species argue against the use of chemical equilibrium models with metallicity as one free parameter in atmospheric retrievals, as different elements can be differently enhanced.
Lunar Xenon from Ancient Earth-Wind
Authors: Bochsler Peter , Rainer Wieler
Published: October 2020

Lunar Xenon from Ancient Earth-Wind The apparent secular variability of the Xe/Kr abundance ratio in the solar wind implanted in grains of the lunar regolith is a long-standing problem (Wieler, 2016): Recently irradiated soils (
The statistical probability of deep flow structures that fit Jupiter's asymmetric gravity
Authors: Duer Keren , Galanti Eli , Kaspi Yohai
Published: October 2020

Juno's measurements of Jupiter's North-South asymmetric gravity field allowed estimating the depth of the zonal jets trough the relation between the measured density anomaly and the flow field. While the deep zonal jets structure has many degrees of freedom, the gravity measurements are manifested only by four gravity harmonics, which implies that the problem is ill-posed. Hence, any suggested solution for Jupiter's deep jets that fit the gravity measurements is non-unique. Here, we perform a thorough statistical analysis of the deep flow structures' range that is bounded by physical considerations. We begin by examining the vertical range of the deep flow, where the meridional structure of the zonal wind is identical to the measured cloud-level profile. Then, we relax the constraint on the meridional profile and allow reasonable variations from the cloud-level profile along with the varying vertical decay. Finally, we examine random meridional profiles that are independent of Jupiter's measured cloud-level profile and explore the possibility that the interior wind structure, which influences the gravity measurements, is entirely different from the cloud-level flow. A sample population of vertical decay structures is used to compare the statistical likelihood of the various cases. We find that only a relatively narrow envelope of vertical solutions can fit the gravity data. Deep flow profiles constructed from perturbations to the cloud-level winds allow a more extensive range of solutions, yet when the patterns differ substantially from the cloud-level observed wind profile, the ability to match the gravity data reduces significantly. Moreover, only 1% of the tested random zonal wind profiles yield any solution that fits the gravity data. Overall, we find that while interior wind profiles that diverge considerably from those at the cloud-level are possible, they are statistically unlikely. In addition to the gravity measurements, Juno's microwave radiometer (MWR) measurements might reveal information about the wind's structure below the cloud level. Inspired by the MWR's nadir brightness temperature estimations, which are dominated by ammonia abundance, we show that depth-dependent flow profiles are still compatible with the gravity measurements if the variation at depth from the measured cloud-level meridional profile is not too substantial.
Water and lava both seem viable for the formation of one of Mars' densest and largest channel networks
Authors: Bernhardt Hannes , Williams David A.
Published: October 2020

The Axius Valles on the Malea Planum region’s (MPR) northern flank down into the Hellas basin are one of the most extensive and densest channel networks on Mars [1,2]. While previous studies tentatively interpreted the area as pyroclastic deposits dissected by sapped water/lahar flows [3-8] we considered their viability versus low-viscosity lava flows. PhysiographyThe Axius Valles and adjacent channels to the west consist of ~22,550 km of mostly parallel sinuous valleys dissecting a plain (drainage density of 0.09 km-1) of gentle but relatively uniform northnortheast tilt, i.e., long-wavelength dip, at ~0.6 to 0.9° (~1 to 1.6%) towards the Hellas basin floor. The channels are up to ~20 km wide and ~100 m deep, although most are narrower and shallower than ~5 km and ~50 m, respectively. The majority of the valleys originates around the rim of Amphitrites Patera between elevations of ~1,200 and ~1,600 m. Smaller subsets originate at or below the rim of Peneus Patera between elevations of ~0 m and ~600 m, or are traceable further south into the wrinkle-ridged plains of the MPR. The longest continuously traceable valley of the Axius Valles is ~325 km long and follows the topographic gradient from ~600 m above the datum down to ~ -4,800 m. The valleys’ sinuosity is relatively low, ranging from ~1 up to ~1.15, and anabranching is very common. In several locations, sinuous valleys are levéed, i.e., bound by ridges that can be up to ~100 m high. DiscussionBased on their morphology and location, the Axius Valles have been tentatively interpreted as the result of sapped water or lahar flows that carved into friable pyroclastic deposits [3-7]. However, diagnostic features such as short, digitate levée-overspill deposits, bulged, lobate flow fronts (both typical for high viscosity flows, i.e., most lavas or mud/sludge), and associated pit-chains (typical for lava tubes, i.e., lava flows) are absent but might have been covered by 10s of meters thick dust-ice mantling [12] or eroded by intense deflation [e.g., 13]. In any case, the fact that the channels extend over 100s of kilometers on a slope of
Earth’s polar outflow evolution from mid-Archean to present
Authors: Kislyakova Kristina , Johnstone Colin , Scherf Manuel , Holmström Mats , Alexeev Igor , Lammer Helmut , Khodachenko Maxim , Güdel Manuel
Published: October 2020

Habitable conditions on Earth developed in a tight connection to the evolution of terrestrial atmosphere which was strongly influenced by atmospheric escape. In this study, we investigated the evolution of the polar ion outflow from the Earth’s open field line bundle starting from mid-Archean (three gigayears ago) and to present. We performed Direct Simulation Monte Carlo (DSMC) simulations and estimated upper limits on escape rates from the Earth's polar areas assuming the present-day composition of the atmosphere. We performed two additional simulations with lower mixing ratios of oxygen of 1% and 15% to account for the composition changes after the Great Oxydation Event (GOE).According to our estimates, the maximum loss rates due to polar outflow was reached three gigayears ago equal to 3.3 x 1027 s-1 and 2.4 x 1027 s-1 for oxygen and nitrogen, respectively. We estimate the total maximum integrated mass loss equal to 39% and 10% of the modern atmosphere's mass, for oxygen and nitrogen, respectively. We also show that escape rates increase, if the oxygen mixing ratio is decreased (GOE simulations), which is due to reduced thermospheric cooling. According to these results, the main factors that governed the polar outflow in the considered time period are the evolution of the XUV radiation of the Sun and the atmosphere's composition. The evolution of the Earth's magnetic field plays a less important role. We conclude that although the atmosphere that has a present-day composition can survive the escape due to polar outflow from 3 gigayears ago and later, a higher level of CO2 between 3.0 and 2.0 Ga is likely necessary to reduce the escape.
Ultra-low frequency foreshock waves at Venus and Mercury in a global hybrid simulation
Authors: Jarvinen Riku , Kallio Esa , Pulkkinen Tuija I.
Published: October 2020

We study the solar wind interaction with Venus and Mercury in a 3-dimensional global hybrid simulation where ions are treated as particles and electrons are a charge-neutralizing fluid. We concentrate on the formation of large-scale ultra-low frequency (ULF) waves in ion foreshocks and their dependence on the solar wind and interplanetary magnetic field conditions. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is smaller than about 45 degrees. The magnetic connection with the bow shock allows backstreaming of the solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter the bow shock. We compare the waves between Venus and Mercury, and analyze the coupling of the ULF waves with the planetary ion acceleration at Venus.References:Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Oxygen Ion Escape From Venus Is Modulated by Ultra-Low Frequency Waves, Geophys. Res. Lett., 47, 11, doi:10.1029/2020GL087462Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Ultra-low frequency waves in the ion foreshock of Mercury: A global hybrid modeling study, Mon. Notices Royal Astron. Soc., 491, 3, 4147-4161, doi:10.1093/mnras/stz3257
The dance of snow-lines
Authors: Owen James
Published: October 2020

Snow-lines are thought to play a vital role in the evolution of protoplanetary discs and planet formation at all scales. Snow-lines occur in regions of the protoplanetary discs where the temperature reaches the sublimation temperature and volatiles transition from the solid phase to the vapour phase (or vice-versa). However, in the outer region of protoplanetary discs (beyond a few AU), the temperature is set by the distribution of solids and their ability to absorb stellar light. Thus, the thermodynamics of the disc and the volatile phases are inextricably linked. In this talk, I will show this coupling is thermally unstable, and snow-lines continually evolve in regions of the disc that are marginally optically thick. Patches of the disc proceeding through a limit cycle, where volatiles in a region of the disc continually condense and then sublimate. Using numerical simulations of the CO snow-line I will show it can move 10s AU over 10,000 years, repeatedly. I will use these simulations to discuss how this new process may effect measured Carbon abundances, solid evolution and ultimately planet formation, making connections to high-resolution images of protoplanetary discs. 