bluuebunny/crossref_metadata_2025 huggingface dataset:
UV Protection of Bacteria Under Simulated Martian Conditions
Authors: Godin Paul , Schuerger Andrew , Moore Casey , Moores John
Published: October 2020

Ultraviolet (UV) irradiation on the surface of Mars is an important factor aﬀecting the survivability of microorganisms on Mars. The possibility of Martian brines made from Fe2(SO4)3, MnSO4, and MgSO4 salts providing a habitable niche on Mars via attenuation of UV radiation was investigated on the bacteria Bacillus subtilis and Enterococcus faecalis. Results demonstrated that it is possible for brines containing Fe2(SO4)3 on Mars to provide protection from harmful UV radiation, even at concentrations as low as 0.5%. Brines made from MnSO4 and MgSO4, did not provide significant UV protection and most spores/cells died over the course of short-term experiments.However, Fe2(SO4)3 brines are strongly acidic, and thus, were lethal to E. faecalis. In contrast, B. subtilis, as a spore-forming bacterium resistant to pH extremes, was unaﬀected by the acidic conditions of the brines and did not experience any significant lethal eﬀects. Any extant microbial life in Martian Fe2(SO4)3 brines (if present) would need to be capable of surviving acidic environments, if these brines are to be considered a possible habitable niche.The results from this work are important to both the search for life on planets with an atmosphere unable to significantly attenuate UV radiation (i.e., like Mars); and for planetary protection, since it is possible that terrestrial bacteria in the genus Bacillus are likely to survive in Fe-sulfate brines on Mars.Furthermore, preliminary work on UV and photosynthetically active radiation (PAR) light transmission and scattering through simulated Martian regolith and rock samples are also presented. Regoliths that block UV but allow for PAR would be likely candidates for supporting bacterial life.
The Lunar Environment Monitoring Station (LEMS)
Authors: Benna Mehdi , Schmerr Nicholas , Sarantos Menelaos , Bailey Hop , Gershman Daniel , Horanyi Mihaly , Sun Xiaoli , Szalay Jamey
Published: October 2020

The Lunar Environment Monitoring Station (LEMS) is an instrument concept funded by NASA’s Development of Advanced Lunar Instrumentation (DALI) Program, and undergoing maturation at NASA's Goddard Space Flight Center. LEMS has been proposed to the NASA's recent call for Payloads and Research Investigations on the Surface of the Moon (PRISM).LEMS is a compact, autonomous, self-sustaining and long-lasting instrument suite that enables in situ, continuous, long-term monitoring of the lunar exosphere and of the most relevant natural and manmade controlling processes (infall of interplanetary dust particles (IDP), influx of solar wind and magnetospheric particles, EUV irradiation, interior outgassing, disturbances by landers and human surface activities). LEMS can be delivered to the surface of the Moon by crewed or robotic missions. Once deployed (on a deck or directly on the surface), LEMS will operate day and night for a nominal duration of 2 years without requiring any additional support or resources from the carrying asset.LEMS integrates a Mass Spectrometer, a Laser Retro-reflector Array, a Lunar Micrometeoroid Monitor, a Lunar Energetic Ion Analyzer, and a 3-axis Seismometer. These sensors will collect concurrent observations that will lead to a comprehensive, time-resolved, and geographically-localized characterization of the composition and dynamics of volatiles gases in the lunar exosphere as a response to variations in solar forcing, IDP flux, seismicity, and known manmade events. Furthermore, owing to its expected longevity, LEMS will also improve upon the success of the Apollo Passive Seismic Experiment (PSE) by providing a new generation of seismological measurements that will address unanswered questions by the PSEs. These questions include the size and state of the lunar core, homogeneity of the mantle, variation in crustal thickness, the mechanism for deep moonquakes, and the relationship between shallow seismicity and the current tectonic state of the lunar crust.With its complementary and integrated multi-sensors and its autonomous concept of operation, LEMS is a science-enabling investigation that combines capabilities, in a single duplicable instrument package. The duplicative nature of the LEMS design enables a network of stations that focuses on exospheric and geophysical measurements at the Moon to become viable options. Finally, the self-sustaining architecture of LEMS provides a model design of future payloads that can take advantage of more commercial or scientific flight opportunities to the Moon while requiring no further support for operation from their carrying assets.
Rocklines of high temperature minerals in the protosolar nebula
Authors: Aguichine Artyom , Mousis Olivier , Devouard Bertrand , Ronnet Thomas
Published: October 2020

In our solar system, terrestrial planets and meteoritical matter exhibit various bulk compositions. To understand this variety of compositions, formation mechanisms of meteorites are usually investigated via a thermodynamic approach that neglect the processes of transport throughout the protosolar nebula. Here, we investigate the role played by rocklines (condensation/sublimation lines of refractory materials) in the innermost regions of the protosolar nebula to compute the composition of particles migrating inward the disk as a function of time. To do so, we utilize a one-dimensional  accretion disk model with a prescription for dust and vapor transport, sublimation and recondensation of refractory materials (ferrosilite, enstatite, fayalite, forsterite, iron sulfur, kamacite and nickel). We find that the diversity of the bulk composition of cosmic spherules can be explained by their formation close to rocklines, suggesting that solid matter is concentrated in the vicinity of these sublimation/condensation fronts. Although our model relies a lot on the number of considered species and the availability of thermodynamic data governing state change, it suggests that rocklines played a major role in the formation of small and large bodies in the innermost regions of the protosolar nebula. The results of our model are consistent with the composition of chondrules and cosmic spherules. Our model gives insights on the mechanisms that might have contributed to the formation of Mercury's large core.
September epsilon Perseid cluster – collisional origin?
Authors: Čapek David , Koten Pavel
Published: October 2020

A bright fireball together with eight fainter meteors on parallel atmospheric trajectories was observed within 2 seconds by Koten et al. (2017). We will present a detailed analysis of this case focused on the collisional origin of the cluster.We first estimate the age of the cluster and ejection velocities assuming influence of solar radiation pressure and taking into account observational uncertainties. Next we consider that the parent meteoroid producing the observed fireball collided with a micrometeoroid and that the eight observed meteors correspond to the largest fragments of the ejected material. We estimate the total ejected mass, distribution of mass and velocity of the impactor, and the probability of such an impact. Finally we discuss how reliable the explanation by the collision is.
On the sodium enhancement in spectra of slow meteors and the origin of Na-rich meteoroids
Authors: Matlovič Pavol , Tóth Juraj , Kornoš Leonard , Loehle Stefan
Published: October 2020

Distinct Na-enhanced and Na-rich meteor spectra have been previously identified by different authors, but the explanation of their origin and interpretation of the corresponding meteoroid composition was lacking. To study this population, we utilized meteor spectra observations of the global AMOS network and high-resolution Echelle spectra of ablating meteorite samples obtained in a high-enthalpy plasma wind tunnel at the IRS facilities in Stuttgart. It was found that most Na-enhanced and Na-rich spectra can be explained by the effect of low meteor speed related to low ablation temperatures and generally do not reflect real meteoroid composition. Spectra obtained by the laboratory experiment simulating low meteor speeds show corresponding Na-rich spectral profiles irrespectively of the meteorite composition. For more clarity in the classification of Na-enhanced and Na-rich meteoroids, we propose new speed-dependent boundaries between the spectral classes. Based on this classification, we reveal real compositional Na enhancement in five cometary meteoroids including two Perseids, an 𝛼-Capricornid, 𝜈-Draconid and a sporadic. The two Na-enhanced Perseids were linked with increased material strength suggesting that the detected increase of volatile content has implications for the meteoroid structure.
Multi-wavelength phase curves of minor bodies
Authors: Alvarez-Candal Alvaro , Campo Bagatin Adriano , Benavidez Paula , Santana-Ros Toni
Published: October 2020

The brightness of minor bodies depends, among other things, on their phase curves. Furthermore, the absolute magnitude, of a minor body is obtained from these curves, requiring observations at different phase angles, thus being impossible to obtain in a single observing night. Large photometric surveys help due to serendipitous observations of minor bodies in different epochs and phase angles.Multiple wavelength phase curves have not been thoroughly explored yet, in particular, the possibility of obtaining photo-spectra (a very low resolving-power spectrum) at zero phase angle, i.e., not affected by phase coloring. In this presentation, we show preliminary results of multi-wavelength phase curves for over a thousand objects obtained using data from the SLOAN moving object catalog and discuss the statistical properties of the sample.
Coordinated measurements during the Cruise phase of BepiColombo: science cases, operational instruments and windows of opportunities
Authors: Hadid Lina ,   BepiColombo coordinated observations working group
Published: October 2020

BepiColombo (ESA/JAXA), Solar Orbiter (ESA/NASA) and Parker Solar Probe (NASA), will be all traveling in the inner heliosphere for 5 years, between the launch of Solar Orbiter (10th February 2020) and the end of the cruise phase of BepiColombo (2018 - 2025). During the five years to come, these three spacecraft missions will cover different radial distances: BepiColombo will evolve between the orbit of Mercury up to Earth (0.3 AU and 0.9 AU), while Solar Orbiter’s highly elliptical orbit will cover distances from 1.02 AU to 0.28 AU, and Parker Solar Probe from about 0.7 AU to 0.04 AU. In addition to these missions, previous and future spacecraft missions will be taking measurements in our solar system (from Venus ~ 0.7 AU till Jupiter 5 AU). The exceptional and complementary plasma instrumental payloads and magnetometers on-board the different satellites will allow us to make unique multi-point measurements in the solar wind. Hence, in this work, we present the potential coordinated observations between at least BepiColombo, Solar Orbiter and Parker Solar Probe (including also other satellites such as probes at L1, or around Venus, Mars and Jupiter). More specifically, in the first part we focus on the different scientific topic that could be studied during the cruise phase of BepiColombo, in the second part we present the related potential operational instruments and in the last part we discuss the different windows of opportunities we have investigated based on different spacecraft geometries.
Wavelet analysis of gravity waves on Venus using radio occultation temperature profiles
Authors: Imamura Takeshi , Mori Ryota , Ando Hiroki , Peralta Javier , Häusler Bernd , Pätzold Martin , Tellmann Silvia
Published: October 2020

Atmospheric gravity waves are thought to play crucial roles in transporting momentum and energy in planetary atmospheres. They are frequently observed as localized quasi-monochromatic wave packets in cloud images, while the vertical structures of the wave packets have not been investigated. The wavelengths and the packet lengths should reflect the generation processes of the respective wave packets. Though wave packets are thought to propagate independently, they are superposed on each other to induce an unstable field. The statistical characteristics of wave packets need to be known to understand the roles of the waves in the development of the atmospheric structure. We study the characteristics of gravity wave packets in Venus’s atmosphere using high vertical resolution temperature profiles obtained by Venus Express and Akatsuki radio occultation experiments with radio holographic methods (Imamura et al. 2018). Localized disturbances are extracted by applying wavelet transform to the vertical temperature distributions. The analysis showed that (1) wave packets having different wavelengths are overlapped with each other, (2) each wave packet typically includes
Influence of a thermal boundary layer on the thermal evolution of Uranus and Neptune
Authors: Scheibe Ludwig , Nettelmann Nadine , Redmer Ronald
Published: October 2020

It has been a long-standing challenge to reconcile the perceived similarities of Uranus and Neptune with their highly different intrinsic heat fluxes. Previous evolution calculations using the conventional assumption of an adiabatic interior yield too high present-day luminosities or - equivalently - too long cooling times for Uranus  (e.g. [1,2]). For Neptune, however, we found that similar assumptions yield too short cooling times [3].One proposed mechanism for reproducing the observed brightness is a conducting interface between the hydrogen- and helium-rich outer part and the ice-rich inner part that would inhibit efficient energy transport across it [4]. In this work, we use our recently developed tool for modelling giant planets based on the Henyey-method for stellar evolutions [5] to investigate such a conducting interface in the planet's interior, examining the influence of parameters such as assumed layer thickness and thermal conductivity on the cooling behaviour. We find that even a thin conductive interface of a few kilometers has significant influence on the planetary cooling. Initially, the presence of such a boundary layer speeds up cooling, while after about 0.1-0.5 Gyr the cooling is slowed down drastically compared to the adiabatic case, similar to what was found for Saturn previously [6]. Our preferred solutions for Uranus suggest equilibrium evolution with the solar incident flux, while for Neptune, we find that plateaus in Teff(t) near its observed value require fine-tuned combinations of layer thickness and thermal conducitivity. [1] Fortney, Ikoma, Nettelmann, Guillot, and Marley (2011). ApJ 729, 32[2] Nettelmann, Helled, Fortney, and Redmer (2013). Planet. Space Sci. 77, 143[3] Scheibe, Nettelmann, Redmer (2019). A&A 632, A70[4] Nettelmann, Wang, Fortney, Hamel, Yellamilli, Bethkenhagen, and Redmer (2016). Icarus 275, 107[5] Henyey, Forbes, and Gould (1964). ApJ 139, 306[6] Leconte and Chabrier (2013): Nat Geosci. 6, 023007
Report on four enstatite-rich regolith grains from the Itokawa asteroid
Authors: Fazio Agnese , Harries Dennis , Langenhorst Falko
Published: October 2020

. IntroductionThe surfaces of the airless solid bodies of the solar system are exposed to the action of the space weathering (i.e., solar wind, cosmic ray and solar flare, and micrometeoroid bombardment) [1].Solar wind causes the formation of layered rims up a few tens of nanometres [2]. Cosmic rays of solar flares produce tracks up to some millimetres depth in the regolith [3]. The effects of the bombardment by micrometeoroids range from the melting and vaporization to shock deformation of the regolith’s grains, causing their fragmentation or the formation of pit-shaped microcraters [1].Enstatite is the second most abundant silicate mineral on asteroid surfaces. Its shock deformation features were reported in numerous meteorites [4]. However, there are no natural reports on the effects of micrometeoroid bombardment. To reproduce such effects, gem-quality oriented enstatite crystals were irradiated by femtosecond pulsed laser [5]. A strong control of the shock direction and a rare occurrence of (100) clinoenstatite lamellae compared to shocked meteorites have been demonstrated [5].Aimed to study the effects of micrometeoroid bombardment on enstatite, four enstatite-rich Itokawa grains allocated from JAXA have been investigated. Micrometeoroid impacts occur stochastically and unfortunately, none of the four requested grains showed microcraters. Despite that, the samples were sliced by focused ion beam (FIB) and then studied by analytical transmission electron microscopy (TEM).Here, we report on the microstructures of these grains and discuss them in terms of parent body and space weathering history.2. SamplesRA-QD02-0205 (#205). It is a prismatic grain (55x43x15 µm3). It is constituted by a single crystal of enstatite (En74.2±3.0Fs24.5±3.0Wo1.7±0.8) that is pervasively crossed by (100) clinoenstatite lamellae. Such lamellae are decorated by dislocations. The grain shows a discontinuous solar wind damaged polynanocrystalline rim (up to 50 nm). The density of solar flare tracks (SFT) is
On the potential role of serpentinization in the thermal evolution of planetesimals in the early outer Solar system
Authors: Farkas-Takacs Anikó , Kiss Csaba , Góbi Sándor , Keresztúri Ákos
Published: October 2020

Some meteorite samples show that in addition to heat from accretion and radioactive decay, there may have been chemical processes that, at least at some point in the history of the Solar System, could significantly alter the lithological characteristics of the objects and contributed notably to internal heat production.We constructed a model considering the chemical process of serpentinization.  Serpentine is a hydrous magnesium phyllosilicate mineral, resulting from the hydration of olivine and/or pyroxene, in an exothermic reaction that takes place in the presence of liquid water.2Mg2SiO4 + 3H2O -> Mg3Si2O5(OH)4 + Mg(OH)2Mg2SiO4 + MgSiO3 + 2H2O -> Mg3Si2O5(OH)4Our model is based on earlier models (Cohen et al., 2000; Góbi et al., 2017) which estimated the serpentinization time scale and examined the effect of interfacial liquid water below the melting point of ice and calculated the necessary initial temperature and the amount of heat produced. We take into account several effects that have previously been neglected.Our results show a significant difference compared with previous outcomes, under the same initial conditions: the reaction time scale increased significantly especially in cases where the initial temperature was below the melting point of water -- in these cases, the difference in the characteristic length of the process was longer by two orders of magnitude. Another significant difference was the extent of the effect of interfacial water, as previous studies found that the process takes place at a similar rate below the freezing point of water as above. Our results show that although the process works below the freezing point it slows down significantly. We also examined whether these chemical processes could take place under the different conditions in the outer Solar System and influence significantly the evolution of the objects there.
Stochastic accretion of the Earth
Authors: Sossi Paolo , Stotz Ingo , Jacobson Seth , Morbidelli Alessandro , O'Neill Hugh
Published: October 2020

The Earth is depleted in volatile elements relative to chondritic meteorites, its possible building blocks. Abundances of volatile elements descend roughly log-linearly with their calculated volatilities during solar nebula condensation [1, 2]. This depletion, however, is not accompanied by any stable isotope fractionation, which would otherwise be expected during vaporisation/condensation and atmospheric loss attending accretion [3, 4]. Thus, the physical processes that led to the formation of the Earth are yet to be reconciled with its chemical composition. Here, we integrate N-body simulations of planetary formation [5] within a framework that combines estimates for the compositions of planetary building blocks with volatile element losses during collisions, to link Earth’s elemental- and isotopic make-up with accretion mechanisms. The smooth pattern of volatile depletion in the Earth reflects the stochastic accretion of numerous, smaller, partially-vaporised precursor bodies whose elemental abundances are set by the heliocentric distances at which they formed. Impact events engender vaporisation, but atmospheric loss is only efficient during the early stages of accretion when volatile species can readily escape the gravitational pull of the proto-Earth. The chemical and isotopic compositions of the most volatile elements are controlled by that of late-accreting material, during which time the proto-Earth is sufficiently large so as to limit atmospheric loss. Stable isotopes of moderately- and highly volatile elements thus retain near-chondritic compositions.[1] O’Neill and Palme (2008), Phil. Trans. R. Soc. 4205-38 [2] Braukmüller et al. (2019), Nat. Geosci., 564-9 [3] Wang and Jacobsen (2016), Nature, 521-4 [4] Sossi et al. 2018, Chem. Geol. 73-84 [5] Jacobson and Morbidelli (2014), Phil. Trans. R. Soc. 20130174
Monitoring of the optical spectrum of comet 2I/Borisov at the VLT
Authors: Jehin Emmanuel , Bin Yang , Hainaut Olivier , Opitom Cyrielle , Manfroid Jean , Moulane Youssef , Fitzsimmons Alan , Snodgrass Colin , Meech Karen
Published: October 2020

2I/Borisov is the first active interstellar comet observed in the Solar Sytem, allowing for the first time to sample the composition of a planetary building block from an extrasolar system. We report on the monitoring of 2I with the FORS low resolution spectrograph of the ESO VLT at Paranal during four months, from November 19, 2019 to March 20, 2020. We collected a dozen spectra at 8 different epochs allowing to follow the evolution of the comet activity and composition around perihelion. We also observed with the same instrumental setup an Oort Cloud comet, C/2019 U6 (Lemmon), at about the same heliocentric and geocentric distance than 2I/Borisov at perihelion (rh=Delta=2 au) and with similar AfRho value and Q(CN) in order to use it as a reference for the Solar System. The usual species are detected in the optical spectrum of 2I (CN, C3, C2, and NH2) and their production rates and abundance ratios are computed. The dust production rate and colors are also derived, compared to C/2019 U6 and other comets of the Solar System, and their evolutions are followed with the heliocentric distance.
 

Fig1. Comparison of the optical spectra of the interstellar comet 2I/Borisov at perihelion (rh=Delta=2,0 au) and the Oort Could comet C/2019 U6 (Lemmon) observed with FORS at the ESO VLT (Paranal Observatory). C/2019/U6 was chosen for comparison as a Solar System comet with a typical composition. It was also at the about the same distances to the Sun and Earth, and it had about the same dust and CN production rates as 2I/Borisov as measured by the TRAPPIST-South telescope.
Peeking inside the Black Box: Interpreting Deep Learning Models for Exoplanet Atmospheric Retrievals
Authors: Yip Kai Hou , Changeat Quentin , Nikolaou Nikolaos , Morvan Mario , Edwards Billy , Waldmann Ingo
Published: October 2020

Deep learning algorithms are growing in popularity in the field of exoplanetary science due to their ability to model highly non-linear relations and solve interesting problems in a data-driven manner. Several works have attempted to perform fast retrieval of atmospheric parameters with the use of machine learning algorithms or deep neural networks (DNNs).  Yet, despite their high predictive power,  DNNs are also infamous for being `black boxes’. It is their apparent lack of explainability that makes the astrophysics community reluctant to adopt them. What are their predictions based on? How confident should we be in them? When are they wrong and how wrong can they be? In this work, we present a number of general evaluation methodologies that can be applied to any trained model and answer questions like these.  In particular, we train 3 different popular DNN architectures to retrieve atmospheric parameters from exoplanet spectra and show that all 3 achieve good predictive performance. We then present an extensive analysis of the predictions of DNNs, which can inform us —among other things — of the credibility limit for atmospheric parameters for a given instrument and model. Finally, we perform a sensitivity analysis to identify to which features of the spectrum the outcome of the retrieval is most sensitive. We conclude that for different molecules, the wavelength ranges to which the DNN’s predictions are most sensitive, indeed coincide with their characteristic absorption regions. The methodologies presented in this work help to improve the evaluation of DNNs and to grant interpretability to their predictions.
The ExoClock Project: an open integrated platform for maintaining the Ariel target ephemerides with contributions from the public
Authors: Kokori Anastasia
Published: October 2020

The ExoClock Project (www.exoclock.space) is an open, integrated, and interactive platform, designed to maintain the ephemerides accuracy of the Ariel targets. Ariel is ESA's medium class space mission prepared for launch in 2028. The main aim of the mission is to characterise a large number of exoplanets to better understand their nature. ExoClock aims to provide transit mid-time predictions for Ariel by collecting all currently available data (literature observations, observations conducted for other purposes, both from ground and space) and by efficiently planning dedicated efforts to follow-up the riel targets. ExoClock is open to contributions from a variety of audiences —  professional, amateur and industry partners — aiming to make the best use of all available resources towards delivering a verified list of ephemerides for the Ariel targets before the launch of the mission. In this presentation strategies, tools and the current status of the ExoClock project will be described in detail. In addition, the first results will be presented briefly and finally, lessons learned and the potential of using similar strategies in other projects will be discussed.
On The Compatibility of Ground-based and Space-based Data: WASP-96 b, An Example
Authors: Yip Kai Hou , Changeat Quentin , Edwards Billy , Morvan Mario , Chubb Katy , Tsiaras Angelos , Waldmann Ingo , Tinetti Giovanna
Published: October 2020

The study of exoplanetary atmosphere relies on detecting minute changes in the transit depth at different wavelengths. To date, a number of ground and space based instruments have been used to obtain transmission spectra of exoplanets in different waveband. One common practice is to combine observations from different instruments in order to achieve a broader wavelength coverage. We present here two inconsistent observations on WASP-96 b, one by Hubble Space Telescope (HST) and the other by Very Large Telescope (VLT). We present two key findings in our investigation: 1.) a strong water signature is detected via the HST WFC3 observations. 2.) A notable offset in transit depth (>1100 ppm) can be seen when the ground-based and space-based observations are combined together. The discrepancy raises the question of whether observations from different instruments could indeed be combined together. We attempt to align the observations by including an additional parameter in our retrieval studies but are unable to definitively ascertain that the aligned observations are indeed compatible. The case of WASP-96 b signals that compatibility of instruments should not be assumed. While wavelength overlaps between instruments can help, it should be noted that combining datasets remains a risky business. The difficulty in combining observations also strengthens the need for next generation instruments which will possess broader spectral coverage.
Heavy positive ion groups in Titan's ionosphere: Cassini Plasma Spectrometer IBS observations
Authors: Haythornthwaite Richard , Coates Andrew , Jones Geraint , Wellbrock Anne , Waite Hunter
Published: October 2020

AbstractData from the Cassini Plasma Spectrometer Ion Beam Spectrometer (CAPS IBS) sensor have been examined for 5 close encounters of Titan during 2009 to examine heavy positive ions. Positive ions with masses between 170 and 310 u/q are examined. Ion mass groups are identified up to 275 u/q with ion groups below 250 u/q having clear structure with a 12-14 u/q spacing between group peaks.The ion group peaks are found to be consistent with masses of polycyclic aromatic hydrocarbon (PAH) and polycyclic aromatic nitrogen heterocyclics (PANH). The ion groups in this study are the heaviest positive ion groups examined so far from in-situ ion data at Titan. Our findings further the understanding of the link between low mass ions and high mass negative ions, as well as the formation of aerosols in Titan's atmosphere.IntroductionTitan is the largest moon of Saturn and has a thick extended atmosphere along with a large ionosphere. The ionosphere has been shown to contain a plethora of hydrocarbon/nitrile cations and anions1.Previous ion composition studies in Titan’s ionosphere by Cassini instruments revealed "families" of ions around particular mass values and a regular spacing of 12 to 14 u/q between mass groups2. These are thought to be related to a carbon or nitrogen backbone that dominates the ion chemistry2. Previous studies also identified possible heavy ions such as naphthalene, anthracene derivatives and an anthracene dimer at 130, 170 and 335 u/q respectively1.  Later flybys demonstrated the existence of even larger positive ions up to masses of 1100 u/q3.Methodology               The Cassini Plasma Spectrometer Ion Beam Spectrometer (CAPS IBS)4 is an electrostatic analyser that measures energy per charge ratios of ions. During the Titan flybys Cassini had a high velocity (~6 km/s) relative to the low ion velocities (
HCl in the atmosphere of Mars: chlorine isotopic ratio
Authors: Trokhimovskiy Alexander , Olsen Kevin , Korablev Oleg , Montmessin Franck , Lefevre Franck , Fedorova Anna , Alday Parejo Juan , Beliaev Denis , Patrakeev Andrey , Shakun Alexey
Published: October 2020

The ExoMars Trace Gas Orbiter (TGO) mission had started regular measurements in 2018. Primary goal of the mission is to quantify trace gases that could indicate geologic or biogenic activity on Mars (Vago et al., 2015). Atmospheric Chemistry Suite mid-infrared channel (ACS MIR) is a high resolution cross-dispersion spectrometer operating in solar occultation mode (Korablev et al., 2018). It was designed to make the most sensitive measurements of the atmosphere to date. During each occultation up to 20 diffraction orders are simultaneously recorded at different tangent altitudes. In 2020 ACS MIR reports the discovery of the gaseous hydrogen chloride (HCl). Absorption features are present in several consecutive diffraction orders, withal both isotopes H37Cl and H35Cl are clearly observed. HCl was observed by ACS simultaneously in both hemispheres after the main phase of the global dust storm. Though the formation mechanism is not fully clear, we believe that the presence of HCl is associated with the lifted dust and chlorine component in it.On Earth, in general, the chlorine isotope variations in nature are relatively small, ranging from ~-2 to +2 ‰. However, large variations are observed, e.g. in extraterrestrial materials and volcanic gases, due to kinetic fractionation. On Mars Farley et al. (2016) reported a range from -1 ‰ to −51 ‰ (5% reduction) for the δ37Cl in the samples drilled in the Gale Crater. ACS observations demonstrate enrichment of the 37Cl up to +250 ‰ on average in the atmospheric gaseous. In principle, most atmospheric elements on Mars have heavy isotope enrichments due to preferential loss of the light isotope to space (e.g. Vandaele et al., 2019). Early hydrodynamic escape during intense extreme ultraviolet radiation followed by prolonged atmospheric ‘erosion’ explains the heavy isotope enrichment. Chlorine loss, as HCl, would raise the δ37Cl value of the residual materials, involved in the dust-atmospheric exchange cycle. ReferencesFarleya K.A., Martina P., Archer P.D. , et al.: Light and variable 37Cl/35Cl ratios in rocks from Gale Crater, Mars: Possible signature of perchlorate, Earth and Planetary Science Letters 438:14-24, DOI: 10.1016/j.epsl.2015.12.013, 2016.Korablev, O., Montmessin, F., Trokhimovskiy, et al..: The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter, Space. Sci. Rev., 214(1), 7, doi:10.1007/s11214-017-0437-6, 2018.Vago, J., Witasse, O., Svedhem, et al.: ESA ExoMars program: The next step in exploring Mars, Sol. Syst. Res., 49(7), 518–528, doi:10.1134/S0038094615070199, 2015.Vandaele, A. C., Korablev, O., Daerden, F. et al.: Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter, Nature, 568, 521–525, doi:10.1038/s41586-019-1097-3, 2019.
New models of Jupiter in the context of Juno and Galileo: signature of a decoupling between the atmosphere and the interior
Authors: Debras Florian , Chabrier Gilles
Published: October 2020

Juno's observations of Jupiter's gravity field have revealed extremely low values for the gravitational moments that are difficult to reconcile with the high abundance of metals observed in the atmosphere by Galileo. Recent studies chose to arbitrarily get rid of one of these two constraints in order to build models of Jupiter.In this presentation, I will detail our new Jupiter structure models reconciling Juno and Galileo observational constraints. These models confirm the need to separate Jupiter into at least 4 layers: an outer convective shell, a non-convective zone of compositional change, an inner convective shell and a diluted core representing about 60 percent of the planet in radius. Compared to other studies, these models propose a new idea with important consequences: a decrease in the quantity of metals between the outer and inner convective shells. This would imply that the atmospheric composition is not representative of the internal composition of the planet, contrary to what is regularly admitted, and would strongly impact the Jupiter formation scenarios (localization, migration, accretion).In particular, the presence of an internal non-convective zone prevents mixing between the two convective envelopes. I will detail the physical processes of this semi-convective zone (layered convection or H-He immiscibility) and explain how they may persist during the evolution of the planet.These models also impose a limit mass on the compact core, which cannot be heavier than 5 Earth masses. Such a mass, lower than the runaway gas accretion minimum mass, needs to be explained in the light of our understanding of the formation and evolution of giant planets.Using these models of Jupiter, I will finally detail the application of our new understanding of the interior of this planet to giant exoplanets. At a time of direct imaging of extrasolar planets and atmospheric characterization of hot Jupiters, a good understanding of the internal processes of planets in the solar system is paramount to make the best use of all the observations.
A large-scale approach to modelling Biosignatures: First Steps
Authors: Cross Thomas , Pignatari Marco , Benoit David , Gibson Brad
Published: October 2020

For this poster I will be presenting the approaches taken to produce synthetic spectra for molecules believed to be biosignatures. In astrochemistry, biosignatures describe a group of molecules which could be produced by life and therefore act as an indication of it. Naturally, by being able to identify these molecules it will be possible to screen exoplanets for the possibility of harbouring life. Recently, Seager, Bains and Petkowski (2016) produced a catalogue of possible biosignatures, which totalled above 14,000 molecules. There are groups such as the ExoMol group which model these molecules at extremely high precision. However, due to the large number of molecules, a high precision method would take an unreasonable amount of time and therefore a faster means of producing spectra is required. The work shown within is designed to be quick and produce data for the full rovibronic spectrum rather than selected bands. I will show that anharmonic corrections are needed to be able to simulate qualitatively correct ro-vibrational transitions. In my method, this is done by implementing TOSH, transition optimised shifted hermites, which was first detailed by Lin, Gilbert and Gill (2007). Finally I will be presenting my latest results using this analytical anharmonic approach. 
A Statistical Analysis of Radar Blackouts at Mars: MARSIS, SHARAD and MAVEN Observations
Authors: Lester Mark , Sanchez-Cano Beatriz , Potts Daniel , Lillis Rob , Orosei Roberto i , Campbell Bruce , Witasse Olivier , Opgenoorth Hermann , Milan Steve , Cartacci Marco , Bernardini Fabrizio , Perry Matthew , Putzig Nathaniel , Blelly Pierre-Louis , Leblanc Francois
Published: October 2020

We present an analysis of radar blackouts observed by MARSIS on Mars Express and SHARAD on Mars Reconnaissance Orbiter for the interval 2006 – 2017.  The period of interest encompasses the extended solar minimum between solar cycles 23 and 24 as well as the solar maximum of cycle 24.  Blackouts have been identified by eye through scanning daily plots of the surface reflection for both radars.  A blackout occurs when, for no apparent instrumental reason, the surface reflection normally expected is either not observed (total) or when the surface reflection is seen for only part of the orbit or the surface reflection is both weaker and spread over a significant time delay (partial).  Such blackouts are caused by enhanced ionisation at altitudes below the main ionospheric electron density peak resulting in increased absorption of the radar signal.  There are more occurrences observed by MARSIS than SHARAD, which is expected due to the lower absorption at the higher operating frequency of SHARAD.  We also observe more blackouts during solar maximum than solar minimum.  Indeed, there are no total blackouts during the extended solar minimum, although both radars do have partial blackouts.  There is no apparent relationship between blackout occurrence and crustal magnetic fields.  Following previous work, which has indicated that solar energetic particles, specifically electrons are responsible for the enhanced ionisation in the atmosphere, we also present the analysis of the MAVEN SEP electrons between 20 keV and 2 MeV during events when all three spacecraft were operational.  We find that the SEP electron flux-energy relationship is much enhanced during the total blackouts, in particular where both radars are impacted, while for partial blackouts the flux-energy spectrum is closer to those from orbits where no blackout occurs.  We also find that for certain events, the average spectrum which result in a blackout is particularly enhanced at the higher energy end of the spectrum, above 50 keV. The average spectra from each condition is presented.  We conclude that there is a higher probability of a radar blackout during solar maximum, that crustal magnetic fields play no apparent role in the their observational occurrence, that the higher energy (< 50 keV) electrons are responsible, and that for events where both radars observe a radar blackout the SEP electron fluxes are at their highest.
The Impact of Scattering Clouds when Studying Exoplanet Emission Spectra with JWST
Authors: Taylor Jake , Parmentier Vivien , Line Michael , Lee Graham , Irwin Patrick , Aigrain Suzanne
Published: October 2020

Observational studies of exoplanets show that many of them contain some form of cloud coverage. The current modelling techniques used in emission to account for the clouds tend to require prior knowledge of the cloud condensing species as well as not considering the scattering caused by the clouds. We explore the effects that scattering has on the emission spectra by modelling a suite of hot Jupiter atmospheres with varying cloud single scattering albedos and temperature profiles. We examine from simple isothermal cases to more complex thermal structures and physically driven cloud modelling. We show that scattering can produce spectral signatures in the emission spectrum even for isothermal atmospheres. We identify the problems that arise from fitting JWST spectra when the spectral shape is dominated by the scattering from the clouds. Finally, we propose a novel method of fitting the single scattering albedo of the cloud in emission retrievals, this technique does not require any prior knowledge of the cloud chemical or physical properties. We show that this technique can retrieve the wavelength dependent shape of the single scattering albedo while accurately modelling the chemistry in the atmosphere.       
A long term study of twilight clouds on Mars based on Mars Express VMC images
Authors: Hernandez Bernal Jorge , Sánchez-Lavega Agustín , Del Río-Gaztelurrutia Teresa , Hueso Ricardo , Ravanis Eleni , Cardesín-Moinelo Alejandro , Wood Simon , Titov Dima
Published: October 2020

During twilight, when the sun is below the horizon, clouds and atmospheric dust can still be illuminated by the sun if they are high enough over the surface, as they escape the shadow of the planet. Observations of this direct illumination can be used to determine the minimum altitude for elevated features. While this is a rare phenomenon on Earth, it is a common occurrence on Mars, where clouds and aerosols can usually reach high altitudes in the mesosphere. Twilight clouds were first observed on Mars by ground-based telescopes, and then by cameras on the Viking orbiters. However, in the last few decades of Mars exploration, most orbiters have been placed in sun-synchronous orbits centered around the afternoon [1], and thus few observations of the twilight have been collected.Mars Express (MEX) is an excellent platform for the study of twilight clouds due to its non-sun-synchronous orbit, The Visual Monitoring Camera (VMC) [2] onboard MEX hasas a wide Field of View (FOV) that allows regular observations of the full disk of Mars (usually including the region in dawn) from the apocenter of the MEX orbit [3]. The current VMC dataset includes ~50 000 images distributed across ~3000 observations (each observation consisting of several consecutive images), covering 8 Martian Years. We have developed a pipeline to perform a the systematic study of twilight clouds in VMC images. As VMC is a broad-band imager, it is not yet possible to properly study the composition of clouds, as the camera cannot distinguish spectroscopically between water ice, dust or CO2. Therefore for simplicity, we use the word “cloud” to refer to these elevated features, regardless of their actual composition.We show some examples of twilight clouds in Figure 1. We find three main groups of twilight clouds in a belt around 45ºS. These three groups correspond to the regions of Terra Cimmeria, Terra Sirenum, and Aonia Terra, where the clouds appear mostly in the southern winter. Additionally, some of the highest clouds we find correspond to these regions. It is worth noting that an extremely high altitude plume was observed, also at dawn, and around the southern winter solstice, over Terra Cimmeria [6].Whilst we find that these twilight clouds are more common during the Aphelion Cloud Belt season (ACB)[4], the latitudinal distribution of clouds differs from that of the ACB, as the biggest concentration of twilight clouds happens in a belt around 45ºS, while the ACB is more or less symmetrical around the equator [5]. This may be explained by the fact that VMC observations are mostly in the early morning, while most ACB studies have been focused on the afternoon [1]. Our results are biased by the fact that we only detect isolated clouds at some altitude over the surface, and that might also be part of the explanation for this discrepancy.References:
Ariel Phase B
Authors: Tinetti Giovanna , Eccleston Paul , Lueftinger Theresa , Pilbratt Goran , Puig Ludovic ,   Ariel team
Published: October 2020

Ariel was selected as the fourth medium-class mission in ESA’s Cosmic Vision programme in the spring 2018. This paper provides an overall summary of the science and baseline design derived during the phase A and consolidated during the phase B1.During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System.Transit, eclipse and phase-curve spectroscopy means that no angular resolution is required. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. Detailed performance studies have demonstrated that the current mission design will achieve the necessary precision to observe all the Ariel target candidates within the mission lifetime.  The baseline integrated payload consists of 1-metre class, all-aluminium, off-axis Cassegrain telescope, feeding a collimated beam into two separate instrument modules. A combined Fine Guidance System / VIS-Photometer / NIR-Spectrometer contains 3 channels of photometry between 0.50 µm and 1.1 µm, of which two will also be used as a redundant system for provided guidance and closed-loop control to the AOCS. One further low resolution (R = ~15 spectrometer in the 1.1 µm – 1.95 µm waveband is also accommodated here. The other instrument module, the ARIEL IR Spectrometer (AIRS), provides spectral resolutions of between 30 – 100 for a waveband between 1.95 µm and 7.8 µm. The payload module is passively cooled to ~55 K by isolation from the spacecraft bus via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling to
Characterisation of V-type asteroids using phase-curves
Authors: Oszkiewicz Dagmara ,   SONATA13
Published: October 2020

Characterisation of the V-type asteroid population may help to comprehend the planetesimal formation and evolution. Asteroid phase-curves are known to relate to surface properties such as asteroid taxonomy, surface roughness, particle size distribution, albedo and many others, providing insight into surface properties of the V-types.Gil-Hutton et al. (2017) showed that the basaltic asteroids display two distinct polarimetric behaviors, which they attributed to the regolith particle size. Considering that phase-curve parameters relate to surface and regolith properties, they may verify those distinct behaviors.We observed about 20 asteroids during around 250 nights (over 500 fragmental lightcurves) to obtain high quality phase curves. We fitted the standard H,G; H,G1,G2, and H, G12 phase functions, limiting them to physical solutions only. This greatly extends the sample of well determined phase-curves for the underrepresented V-types. For asteroids with data from multiple oppositions we used a simultaneous fit assuming the same slope parameters in all apparitions and different absolute magnitude values. From these data we also derived the G12* parameter to be used in single parameter phase functions recommended for fitting low quality photometry. We do not find substantial evidence for any clustering into distinct phase curve parameters groups as suggested by Gil-Hutton et al. 2017. Only one asteroid (2763 Jeans) shows an exceptionally high G2 value.Further work should be conducted to determine slope parameters of more V-types to further verify the division of V-type asteroids into two distinct groups. Obtaining phase curves of non-Vestoids (such as those in the mid and outer Main Belt) may also help clarify if the division into distinct V-type groups is due to particle size or mineralogical differences.