bluuebunny/crossref_metadata_2025 huggingface dataset:
Planet Formation in Transition Discs
Authors: Cummins Daniel , Owen James
Published: October 2020

High-resolution imaging of protoplanetary discs has revealed their wealth of substructure. Perhaps the most striking observation has been the presence of large-scale crescent-shaped features, which have been interpreted as large quantities of dust trapped in anticyclonic vortices. Such regions of high dust-to-gas ratios are expected to promote planet formation processes, so understanding their formation and evolution is of primary interest.Gas-only hydrodynamics simulations have demonstrated that the thermal feedback from a planetary embryo undergoing rapid formation by pebble accretion can trigger the generation a large-scale vortex. However, the ability for such a vortex to trap dust and the impact this has on the forming planet are yet to be investigated. I will present results from hydrodynamics simulations of a disc containing both gas and dust, showing the efficiency with which dust grains accumulate in a vortex, and discuss the consequences this has for the growth of the planetary embryo.
Deciphering the Solar Wind at Saturn
Authors: Gould Wayne , Ray Licia , Arridge Chris S.
Published: October 2020

The effects of the solar wind on Saturn’s magnetosphere are poorly constrained as there are no consistent solar wind monitors upstream of the planet. This has limited previous studies of the solar wind’s influence on the Saturnian magnetosphere to case studies and time dependant analyses of intervals of the Cassini data. While useful and enlightening, these methods assume a priori, a relationship between the solar wind and magnetospheric driving or are biased due to their selection based on particular events detected within the magnetosphere.   Mutual information is a measure of information gain and is measured by the change in uncertainty, after the reception of an input variable in relation to a related output variable. The more mutual information in a system between two variables, the stronger the relationship between the two. We apply Mutual Information Theory to investigate the statistical relationship between solar wind parameters e.g. density, magnetic field strength, velocity, and magnetospheric driving. We consider the entire Cassini dataset, identifying intervals where the Tao et al. [2005] solar wind propagation model is valid. This robust statistical analysis determines magnetospheric proxies for the solar wind and, crucially, how much information these proxies provide about the state of the solar wind. Finding and confirming the relation of these indirect proxies to solar wind propagation models presents the opportunity to open long time scale data to interpretation with respect to the solar wind’s behaviour at the outer planets, using data from past missions. Initial results indicate that the direction of the IMF plays a stronger role in driving Saturn’s magnetosphere than previously thought and identifies potentially new solar wind parameters that effect Saturn’s magnetosphere. 
Spatial and temporal variability of UV albedo and its relation to the wind field revealed by Akatsuki UVI
Authors: Iwanaka Tatsuro , Imamura Takeshi , Lee Yeon Joo , Yamazaki Atsushi
Published: October 2020

Venus is entirely covered by optically thick clouds that play essential roles in the Venus' climate system. The cloud consists of H2SO4 aerosols, and H2SO4 is produced from SO2 photochemically at the cloud top. SO2 is abundant in the lower part of the cloud layer and the subcloud region (Bertaux, 1996), and is thought to be transported to the cloud top in the sulfur cycle (Mills et al., 2007), although the dynamical processes responsible for the transport are not understood. The purpose of our study is to confirm that SO2 is supplied from the lower atmosphere to the cloud top where it is lost via photochemical reactions and to determine how the stationary planetary-scale circulation and time-varying disturbances contribute to the SO2 transport. The horizontal divergence calculated from the cloud-tracked wind (Ikegawa and Horinouchi, 2016; Horinouchi et al., 2018) is considered as an index of the vertical flow in the cloud: a horizontally divergent (convergent) flow will tend to correspond to an upward (downward) wind for convection-like motions, while the divergence is out of phase with the vertical wind by 90 degrees for gravity waves including thermal tides. The 283-nm radiance, which is subject to SO2 absorption, measured by Akatsuki UVI (Yamazaki et al., 2018) was converted to UV albedo following the method of Lee et al. (2015, 2017), and low (high) albedo regions are considered to be regions of high (low) SO2 density. By comparing the Lagrangian derivative of UV albedo with the horizontal divergence, the relation between the change of the cloud-top SO2 and the vertical flow was obtained for independent air parcels and the mean field. The result shows that the solar-fixed structure of the UV albedo is consistent with the supply of SO2 by the updraft phase of  the thermal tides and that transient and localized UV albedo variations are consistent with the supply of SO2 by ascending flows coincident with horizontal divergences.
Chemical inventory of a planet hosting disk
Authors: Facchini Stefano
Published: October 2020

PDS 70 is the only disk known to date that hosts two massive planets clearing a large cavity in the dust distribution. The planets have been detected in both infrared and Halpha, indicating that they are still actively accreting from the planet-hosting environment. The elemental composition of the growing planetary atmospheres are bound to be related to the composition of the accreting material. Bright molecular lines of simple chemical species can be used to infer chemical properties of the material that is being accreted by the planets (as C/O and C/N ratios), as well as physical processes presently occurring in the disk (shocking of gas onto the circumplanetary disks, ionisation). In this talk, I will show new ALMA band 6 observations of PDS 70 at moderate angular resolution in two spectral settings targeting HCN and CO isotopologues, small hydrocarbons, H2CO, H13CO+ and simple S bearing molecules. The molecular emission is particularly bright, with 15 molecular lines detected and imaged. The radial and azimuthal structures of the different molecules provide unique information on the chemical and physical conditions of PDS 70.
Radio Astronomy from a Lunar Environment Precursor Tests
Authors: Laffan Downes Eibhlin , Foing Bernard
Published: October 2020

Performing radio astronomy observations from the Earth’s surface is plagued with interference issues. The Earth and its surrounding atmosphere, particularly our ionosphere, are massive sources of natural interference. There are also human sources of interference. There have been several studies attempting to solve the issues surrounding radio observations. One such solution is to find radio-quiet zones, such as the far side of the Moon. In his article "Farside explorer: unique science from a mission to the farside of the moon" David Mimoun states that the Moon is "the most radio-quiet environment in near-Earth space." [1] The far side of the Moon is insulated from Earth's various interference sources. This certainly makes it a great candidate for radio astronomy. [2][3] Due to the rotation and orbiting speed of the Moon, the same side of the Moon is always facing Earth. However, the building of a radio antenna array on the Moon and operating it would be costly. Therefore, tests must be prepared on Earth in advance. These tests are performed with the EuroMoonMars project. Using the Radio Jove receiver with dipole antennae, Solar and Jovian observations will be performed. These observations can be compared with data from other radio telescopes and arrays. This would allow radio astronomy to be tested both as a concept and as a prediction tool for solar weather. Even though the Earth is protected by our atmosphere, the Earth is affected by solar weather. [4] The near side of the Moon will be affected by solar weather and this could be predicted and diagnosed by radio instruments.  During the COVID-19 pandemic and lockdown, observations have been carried out in Bray, Ireland and at The European Space Technology and Research Centre (ESTEC) and Leiden in the Netherlands. These locations are all at similar latitudes. Further observations are planned in Iceland. The EuroMoonMars is launching the CHILL-ICE campaign in 2021 and radio observations will be an integral research topic. Experiments will be carried out to determine the angular response and efficiency of the apparatus in a volcanic region. The rest of the EuroMoonMars CHILL-ICE team deserve thanks for their support of these experiments. The Earth-based apparatus contains a single dipole, the Radio Jove receiver and a laptop to receiver processed data. The experimental methods can be defined as follows:                                                                                                 Graph 1: Data recorded in Radio Skypipe software, taken on the 15th June 2020, during reported solar prominences. References:
Metals in the day-side of ultra-hot Jupiter atmospheres: a key test for planetary formation
Authors: Pino Lorenzo , Désert Jean-Michel , Brogi Matteo , Nascimbeni Valerio , Bonomo Aldo Stefano , Line Michael , Maggio Antonio
Published: October 2020

Ultra-hot Jupiters (Teq ≥ 2,500 K) are the hottest gaseous giants known. They emerged as ideal laboratories to test theories of atmospheric structure and its link to planet formation. Indeed, because of their high temperatures, (1) they likely host atmospheres in chemical equilibrium and (2) clouds do not form in their day-side. Thousands of lines of refractory elements such as iron, normally inaccessible in planets, can be studied through high spectral resolution emission spectroscopy, providing a first look into the chemistry of refractory elements in exoplanets. In this talk we report the detection of neutral iron in the day-side emission spectrum of KELT-9b (Tday ~ 4,000  K), the first detection of an atomic species in the emission spectrum of an exoplanet, obtained with HARPS-N optical data gathered in the framework of the GAPS collaboration. Our detection unambiguously indicates the presence of a thermal inversion in the atmosphere of the planet. We also present a new technique to extract planetary parameters from the cross-correlation function in a statistically sound framework, which makes possible the combination with information from the planetary continuum that can be obtained with complementary space facilities. This is a crucial step towards the measurement of metal abundances in exoplanets, a quantity that can be compared to predictions of planet formation theories. In the near future, our technique will be extended to cooler exoplanets. In the era of EELTs and JWST, this kind of measurements could ultimately open a new window on exoplanet formation and evolution.
Activity evolution for F, G, K, and M dwarfs and the importance for planetary atmospheres
Authors: Johnstone Colin
Published: October 2020

The magnetic activity of stars is a crucially important factor influencing planet formation processes and the subsequent evolution of planetary atmospheres. Understanding how stellar activity evolves for stars with different masses is crucially important for understanding the effects of stellar winds and radiation at X-ray and ultraviolet wavelengths on the erosion of circumstellar disks and planetary atmospheres. I will present a new and comprehensive description of the rotational evolution of stars and the resulting evolution of X-ray and ultraviolet emission for F, G, K, and M dwarfs. I will demonstrate the importance of the star's initial rotation rate on the subsequent activity evolution and clarify common misunderstandings regarding the dependence on stellar mass, including the common belief that M dwarfs are more XUV active than G dwarfs. I will show why these results are important for the evolution of planetary atmospheres.
Destabilization of methane clathrate hydrate by meteorite impacts on present-day Mars
Authors: Gloesener Elodie , Temel Orkun , Karatekin Özgür , Joiret Sarah , Dehant Véronique
Published: October 2020

The series of methane detection and non-detection in the atmosphere of Mars over the last two decades has raised numerous questions about methane generation and destruction mechanisms, which still remain unexplained.  It has been suggested that Martian methane could have a biological origin and be generated by organisms living in the subsurface where conditions are more hospitable [1]. Methane could also be produced through several abiologic processes, including Fischer-Tropsch Type (FTT) reactions where H2 reacts with CO2 in the presence of a metal catalyst [2]. The H2 necessary for the FTT reactions can be produced by several processes and notably by serpentinization [3]. Many of the proposed generation mechanisms for methane would take place hundreds of meters to several kilometers deep in the crust of Mars. Once produced, methane can migrate upwards and be either directly released at the surface or trapped in subsurface reservoirs, such as clathrate hydrates, where it could accumulate over long time before being episodically liberated during destabilizing events. These phenomena leading to surface degassing imply a change in temperature/pressure conditions of the methane reservoirs and are multiple: faulting and landslide generated by seismicity, impact, climatic changes...In this study, we investigate the capacity of small-sized (a few tens to a few hundred meters diameter) impact craters to thermally penetrate the Martian ground and release methane through the dissociation of subsurface clathrate reservoirs. The impacts of small meteorite are more frequent on present-day Mars and could represent a likely process that would sporadically destabilize shallow gas reservoirs, inducing the degassing of methane in the atmosphere of the planet. We use a one-dimensional finite difference thermal model of the subsurface to calculate the depth of stable methane clathrate hydrates. The impact-induced heat, calculated using the Murnaghan equation of state, is then added to geothermal temperatures to obtain the post-impact temperature distributions similarly to [4]. We apply our model to different case studies in order to constrain the impactor radius, velocity and impact angle required to destabilize a subsurface clathrate layer that would discharge methane amounts corresponding to the observations.AcknowledgementsThis work was supported by the Fonds de la Recherche Scientifique - FNRS and by the Research Foundation Flanders (FWO) under Grant n° EOS-30442502.References[1] Atreya, S. K. et al., Planet. Space Sci. 55, 358-369, 2007.[2] Oehler, D. Z. and Etiope, G., Astrobiology 17, 1233-1264, 2017.[3] Oze, C. and Sharma, M., Geophys. Res. Lett. 32, 2005.[4] Schwenzer, S. P. et al., Earth Planet. Sci. Lett. 335-336, 9-17, 2012.
Connecting Jupiter's Auroral Pulsations with In-situ Measurements by Juno
Authors: Dunn William , Yao Zhonghua , Woodfield Emma , Sulaiman Ali , Kurth William , Grodent Denis , Elliott Sadie , Hospodarsky George , Imai Masafumi , Wibisono Affelia , Weigt Dale , Kotsiaros Stavros , Branduardi-Raymont Graziella , Clark George , Bonfond Bertrand , Haewsantati Kamolporn , Rae I. Jonathan , Manners Harry , Rodriguez Pedro , Ness Jan-Uwe ,   William Dunn
Published: October 2020

In 1979, the Voyager spacecraft arrived at Jupiter. Amongst their rich array of discoveries, they identified bright bursts of radio emission at kHz frequencies1, often called quasi-periodic (QP) bursts, and discovered Jupiter’s ultraviolet (UV) aurora2 - the most powerful aurora in the Solar System3. The same year that the Voyager spacecraft explored the Jovian system, the Einstein X-ray Observatory took the first X-ray images of Jupiter4 and discovered that planets can also produce bright and dynamic X-ray aurora5,6. Over the subsequent decades, these distinct multi-waveband emissions have all been observed to pulse with quasi-periodic regularity7–10. Here, we combine simultaneous observations by the Juno spacecraft with the X-ray and UV observatories: XMM-Newton, Chandra and the Hubble Space Telescope. These observations show that the radio, UV and X-ray pulses are all synchronised, beating in time together. Further, they reveal that the X-ray and radio pulses share an identical 42.5 minute periodicity with simultaneously measured compression-mode Ultra Low Frequency (ULF) waves in Jupiter’s outer magnetosphere11. ULF waves are known to modulate wave-particle interactions that can cause electron and ion precipitation, providing a physically consistent explanation for the observed simultaneous ion and electron emissions.  The unification of Jupiter’s X-ray, UV and radio pulsations and their connection to ULF waves provides fundamental and potentially universal insights into the redistribution of energy in magnetised space environments.
Dust Particle Tracking at Comet 67P/Churyumov–Gerasimenko
Authors: Pfeifer Marius , Agarwal Jessica
Published: October 2020

We present the newest iteration of our particle tracking algorithm and highlight findings based on its application to different data sets. The intended use of the algorithm is to analyze image sequences taken by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) of the Rosetta spacecraft during the outbound perihelion phase of comet 67P/Churyumov-Gerasimenko. During this active phase, a lot of material was being ejected, in part as relatively large, boulder-sized objects (dm to m). With our work, we hope to better understand the processes that are responsible for the ejection and those that might affect the flight path of the particles once they are lifted. 
The science return of the ESA Hera mission to the binary asteroid Didymos
Authors: Michel Patrick , Kueppers Michael ,   Hera Investigation Team
Published: October 2020

The Hera mission has been approved for development and launch in the new ESA Space Safety Programme by the ESA Council at Ministerial Level, Space19+, in November 2019. Hera will both offer a high science return and contribute to the first deflection test of an asteroid, in the framework of the international NASA- and ESA-supported Asteroid Impact and Deflection Assessment (AIDA) collaboration.The impact of the NASA DART (Doube Asteroid Redirection Test) spacecraft on the natural satellite of Didymos in October 2022 will change its orbital period around Didymos. As Didymos is an eclipsing binary, and close to the Earth on this date, the change can be detected by Earth-based observers. ESA’s Hera spacecraft will rendezvous Didymos four years after the impact. Hera’s instruments will perform the measurements necessary to understand the effect of the DART impact on Didymos’ secondary, in particular its mass, its internal structure, the direct determination of the momentum transfer and the detailed characterization of the crater left by DART. This new knowledge will also provide unique information on many current issues in asteroid science.From small asteroid internal and surface structures, through rubble-pile evolution, impact cratering physics, to the long-term effects of space weathering in the inner Solar System, Hera will have a major impact on many fields. For instance, collisions play a fundamental role in our Solar System history, from planet formation by collisional accretion to cratering of solid surfaces and asteroid family formation by collisional disruption. The fully documented hypervelocity impact experiment provided by DART and Hera will feed collisional models with information obtained at actual asteroid scale and for an impact speed (~6 km/s) that is close to the average impact speed between asteroids in the main belt. Moreover, Hera will perform the first rendezvous with an asteroid binary, characterize the smallest object ever visited (165 m in diameter) and provide the first direct measurement of an asteroid interior. Additionally, studies using Hera data will in turn affect our understanding of the asteroid population as a whole. The scientific legacy of the Hera mission will extend far beyond the core aims of planetary defense.Acknowledgment: The authors acknowledge funding support from ESA and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870377 (project NEO-MAPP), from the European Space Agency and from the French space agency CNES.
Physically-Consistent Multi-Dimensional Temperature Structure for Retrieval
Authors: Blecic Jasmina
Published: October 2020

The planetary multi-dimensional nature poses many challenges to their atmospheric modeling. However, as targets and data quality improve with the TESS and CHEOPS missions and soon to be launched JWST, PLATO and ARIEL missions, so too must our modeling approach if we would like to assess a truly 3D picture of planetary atmospheres. We present a physically-consistent GCM-motivated multi-dimensional temperature model, that utilizes the dominant dynamical property of short-period tidally-locked planets, the planetary jet, and accounts, for the first time, for the advection of energy around the planet. In our approach, we utilize a tractable set of parameters efficient enough to enable Bayesian analysis and return physical insights not yet retrieved for exoplanets. By fundamentally linking the planetary longitudes and retrieving spectra at all orbital phases simultaneously, we recover three essential properties of the planetary jet (phase offset, amplitude, and pressure where the jet is located) together with the self-consistent temperature structure.                                            Figure 1: Two examples of our parameterized advective temperature component at the equator.
Inclusion of scientific algorithms in MATISSE
Authors: Rognini Edoardo , Zinzi Angelo , Grassi Davide , Adriani Alberto , Mura Alessandro , Capria Maria Teresa ,   JIRAM team
Published: October 2020

MATISSE (Multi-purpose Advanced Tool for the Solar System Exploration) [1] is a tool that allows the visualization of observations from space missions and datasets derived from these observations on  a  three-dimensional  model  of  the  selected  target  body.  The  second  version  of  the  tool  (named MATISSE  2.0 –https://tools.ssdc.asi.it/Matisse)  will,  among  other  things,  include  algorithms developed  by  partner  research  teams;  in  this  work  we  focalize  our  attention  on  the  MATISSE inclusion of two codes developed for atmospheric retrieval and thermophysical modeling. The retrieval code is used for the analysis of the spectra provided by the JIRAM instrument (Jovian Infrared Auroral Mapper [2]) onboard the NASA’s Juno mission, whose main purpose is the study of the upper regions of Jupiter’s atmosphere in the 2-5 μm wavelength range and pressure up to 5-7 bar. The spectra provided by the instrument are processed with the retrieval code that calculates, for each pixel of a hyperspectral image, the chemical and physical parameters in the corresponding points of the  atmosphere  [3].  The  code  processes  all  pixels  of  a  hyperspectral  image,  so  parallelization  is convenient  in  order  to  reduce  the  computation  time;  this  is  possible  by  using  the  Python  language tools, which allow the execution of a code written in its own language (FORTRAN in this case) by providing  the  required  parallelization. As a further optimization step,  the  code has been converted into a Docker image to make it portable and easy to run on heterogeneous architectures. The second  code  included  in  MATISSE  is  a  thermophysical  model  that  calculates  the  surface temperature of airless bodies as function of thermal conductivity [4,5] and other physical properties; the calculated temperature can be compared with the measured ones, if any, in order to retrieve the thermal properties of the soil, or can be used to compute other temperature-dependent quantities. At the present time this code is going to be used for Mercury and Ceres and is almost ready to be included in MATISSE 2.0.[1] Zinzi, A., et al. (2016), Astronomy & Computing, 15, 16-28[2] Adriani, A., et al. (2017), Space Science Reviews, 213, 393-446[3] Grassi et al. (2010), Planetary and Space Science, 58, 1265-1278[4] Capria, M. T. et al (2014), Geophysical Research Letters, 41, 1438-1443[5] Rognini et al. (2019), Journal of Geophysical Research, https://doi.org/10.1029/2018JE005733
Parameterisations of interior properties of rocky planets
Authors: Noack Lena , Lasbleis Marine
Published: October 2020

Observations of Earth-sized exoplanets are mostly limited to information on their masses and radii. Simple mass-radius relationships have been developed for scaled-up versions of Earth or other planetary bodies such as Mercury and Ganymede, as well as for one-material spheres made of pure water(-ice), silicates, or iron. However, they do not allow a thorough investigation of composition influences and thermal state on a planet’s interior structure and properties.As shown in Figure 1, we investigate the structure of a rocky planet shortly after formation and at later stages of thermal evolution assuming the planet is differentiated into a metal core and a rocky mantle (consisting of Earth-like minerals, but with a variable iron content).Fig. 1: Temperature (left), pressure (centre), and density (right) profiles for two example planet masses of one and two Earth masses consideringthe hot temperature scenario and assuming di erent planet iron contents. From Noack and Lasbleis, 2020.We derived possible initial temperature profiles after the accretion and magma ocean solidification following Stixrude (2014). We then developed parameterisations for the thermodynamic properties inside the core depending on planet mass, composition, and thermal state. We provide the community with robust scaling laws for the interior structure, temperature profiles, and core- and mantle-averaged thermodynamic properties for planets composed of Earth’s main minerals but with variable compositions of iron and silicates, see Figure 2. Fig. 2: Comparison between interior structure model data (filled circles) and predicted data from our parameterised model (black empty circles)for different planet parameters and planet masses, with colours ranging from 0.8 (dark blue) to 2 (yellow) Earth masses. Grey circles show theindividual errors. The mean error with one standard deviation is listed for each error plot. From Noack and Lasbleis, 2020. The interior structure profiles, an online tool and the link to the repository including all Python Jupyter notebooks, that were needed to derive the scaling laws and figures of this study, as well as an implementation of the scaling laws in Python are available on the following website: http://geodyn-chic.de/tools.The scaling laws make it possible to investigate variations in thermodynamic properties for different interior thermal states in a multitude of applications such as deriving mass-radius scaling laws or estimating magnetic field evolution and core crystallisation for rocky exoplanets. ReferencesStixrude, L. 2014, Philos. Trans. R. Soc. A: Math. Phys. Eng. Sci., 372, 20130076Noack, L. and Lasbleis, M. 2020, A&A, 638, A129
Coma Anisotropy and the Rotation Pole of Interstellar Comet 2I/Borisov
Authors: Kim Yoonyoung , Jewitt David , Agarwal Jessica , Mutchler Max , Hui Man-To , Weaver Harold
Published: October 2020

We present Hubble Space Telescope observations of interstellar comet 2I/Borisov on five occasions between UT 2019 October 12 and 2020 January 29. Our high-resolution images show persistent asymmetry in the dust coma (Figure 1), best explained by a thermal lag on the rotating nucleus, with peak mass loss occurring in the comet nucleus afternoon (Figure 2). In this interpretation, the nucleus rotates with an obliquity of 30 deg (pole direction R.A. = 205 deg and decl. = 52 deg). The subsolar latitude varied from -35 deg (southern solstice) at the time of discovery to 0 deg (equinox) in 2020 January, suggesting that long-term variations in the coma brightness and activity level may be influenced by seasonal effects (Figure 3). Our model shows that newly reported photometric outbursts (Drahus et al. 2020) and the release of a fragment (Jewitt et al. 2020) could result from a seasonal effect, as the northern hemisphere is illuminated for the first time.Reference: Kim, Y., et al. 2020, ApJL, 895, L34. Figure 1: HST images of 2I/Borisov marked with UT dates of observation. Isophotal contours and extended antisolar and negative velocity vectors (dashed lines) are overlaid to highlight an asymmetry in the coma. Figure 2: Best-fit solutions for the model jet direction (red circles and dashed line), showing a systematic drift with time from 2019 October to 2020 January. The solutions follow the changing projected direction of the Sun (black squares and solid line), but are offset from it by ~20 deg. The existence of this offset suggests a thermal lag on the rotating nucleus. Figure 3: Subsolar (red) and sub-Earth (blue) latitude of 2I/Borisov as a function of time, together with the heliocentric distance (black solid line) on the right axis. We assumed a rotation pole orientation of R.A. = 205 deg and decl. = 52 deg. 
Carbon-grain sublimation: a new top-down component to protostellar chemistry
Authors: van 't Hoff Merel , Bergin Edwin , Jorgensen Jes , Blake Geoffrey
Published: October 2020

One of the main goals in the fields of exoplanets and planet formation is to determine the composition of terrestrial, potentially habitable, planets and to link this to the composition of protoplanetary disks. A longstanding puzzle in this regard is the Earth's severe carbon deficit; Earth is 2-4 orders of magnitude depleted in carbon compared to interstellar grains and comets. The solution to this conundrum is that carbon must have been returned to the gas phase in the inner protosolar nebula, such that it could not get accreted onto the forming bodies. A process that could be responsible is the sublimation of carbon grains at the so-called soot line (~300 K) early in the planet-formation process. I will argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line around protostars, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (~100 K). Moreover, I will show that such characteristics have indeed been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in observational settings or related to the episodic nature of protostellar accretion. If this process is active, this would mean that there is an heretofore unrecognized component to the carbon chemistry during the protostellar phase that is acting from the top down - starting from the destruction of larger species - instead of from the bottom up from atoms. In the presence of such a top-down component, the origin of organic molecules needs to be re-explored. 
Mantle evolution in terrestrial planets - Partitioning behavior of heat producing elements
Authors: Schmidt Julia M. , Noack Lena
Published: October 2020

Melting processes inside the mantle of terrestrial planets are highly dependent on the planet’s heat budget and trigger the redistribution of incompatible trace elements from solid mantle rocks into the melt. Due to density contrasts, convective mantle motion, and other physical factors, this melt ascents towards the surface and takes most of these incompatible elements with it. Some of these ascending elements like 40K, 232Th, and 238U, are radioactive and are important contributors to the Earth’s or other terrestrial planet’s heat budget. By redistributing these elements, the mantle is left depleted and the surface enriched, leading to a shift in the production of heat from the mantle towards the crust.To be able to calculate the amount of redistributed heat producing elements, we model partition coefficients after Blundy and Wood 2003 [1] depending on temperature, pressure, and melt composition and trace them in a global convection code (Fig.1). For the incorporation of the elements’ partitioning behavior at higher upper mantle pressures, we took the thermodynamic approach from Blundy et al. 1995 [2] and parameterized it to higher pressures (Fig.2). The redistribution of heat producing elements between the mantle and crust has important implications for the cooling behavior of the interior. In turn, the latter affects the generation of melt in the mantle and the formation of crust.[1] Blundy, J.D. and Wood, B.J. (2003), RiMG, 52 (1), 59–123.[2] Blundy, J.D., Falloon, T.J., Wood, B.J., and Dalton, J.A. (1995), J. Geophys. Res., 100, 15501-15515. Fig. 1: Redistributed amount of the heat sources 40K, 232Th, and 238U on Mars after 600 Myrs. Fig. 2: The clinopyroxene/melt partition coefficient of Na parameterized to higher pressures. With increasing pressures, partition coefficients increase. At the turning point, the model ceases to work. The applicability of the approach could be increased from 0-4 GPa to ≤12 GPa.
HiRISE-scale characterization of the Oxia Planum landing site for the Exomars 2022 Mission
Authors: Sefton-Nash Elliot , Balme Matt , Quantin-Nataf Cathy , Fawdon Peter , Volat Matthieu , Hauber Ernst , Orgel Csilla , Frigeri Alessandro , Le Deit Laetitia , Ruesch Ottaviano , Adeli Solmaz , Loizeau Damien , Davis Joel , Grindrod Peter , Nass Andrea , de Witte Sander , Calef Fred J. , Soliman Tariq K. , Vago Jorge L. ,   ExoMars Rover Science Operations Working Group (RSOWG) Macro Mapping Team
Published: October 2020

Introduction: Oxia Planum (OP) is the selected landing site for the ESA-Roscosmos ExoMars Programme’s 2022 mission (Figure 1). The descent module and landing platform, Kazachock, will transport the Rosalind Franklin Rover to OP. With the primary goal of searching for signs of past and present life on Mars, Rosalind Franklin will investigate the geochemical environment in the shallow subsurface [1].Figure 1: A) Locations of OP on (A) Mars and (B) in Arabia Terra. Phyllosilicate detections are in red [2]. Estimated/study landing ellipses are in yellow. -3000 m contour is shown in blue. Fluvial channels and sediment fan remnants are evident. C) Designation of mapping ‘Areas’. Oxia Planum: OP lies at the transition between the ancient terrain of Arabia Terra and Chryse Planitia (Figure 1). OP forms a shallow basin, open to the north, characterized by clay-bearing bedrock, and contains units from ~mid-Noachian to ~early-Amazonian in age [3, 4]. There have been at least two distinct phases of aqueous activity within the landing site area. A first phase during the mid-Noachian (estimated age is 4.0 Ga) resulted in ~100 m of layered clay-rich deposits. These comprise Mg/Fe smectites overlain by more Al-rich materials. After a substantial hiatus the second phase of aqueous activity included a fluviodeltaic system. This fluvial activity post-dates the clay-rich layered unit, and is associated with the younger set of channels in Coogoon Vallis, which feeds into the Oxia basin. There is abundant evidence for intense erosion across OP. There are isolated buttes, perhaps remnants of a once-extensive layer that superposed the clay-bearing unit, and a dark, mafic-rich, resistant unit of Amazonian age (
Further constraints on activity models of comet 67P/Churyumov-Gerasimenko with Rosetta data
Authors: Attree Nicholas , Jorda Laurent , Groussin Olivier , Marschall Raphael
Published: October 2020

Cometary outgassing produces a back-reaction force on a nucleus that can alter its trajectory and rotation state. Understanding this activity is key to exploring the physics of the upper layers of cometary surfaces, with implications for their formation and subsequent evolutionary history, and can be constrained by observing the orbit and rotation changes. For comet 67P/Churyumov-Gerasimenko, detailed measurements have been made by the Rosetta spacecraft and various attempts have been made to model the activity (see, e.g. [1,2]).Here we will present updated work using the activity model of [2] to fit to Rosetta outgassing, trajectory, and rotation data. We test a number of different activity distributions over the surface of the comet by varying the Effective Active Fraction (EAF), relative to pure water ice, of facets on a shape model. The previous work has shown that, in order to fit the fast ramp-up and fall-off in outgassing either side of perihelion, 67P’s EAF must vary with time. We therefore investigate a number of different EAF curves to see if different parametric models can be ruled out. The objective here is to constraint the shape of the activity curve that a more advanced thermo-physical model (see, for example [3,4]) must produce in order to fit the data. We also investigate different spatial patterns in EAF, and attempt to correlate them to physical features on the cometary surface. Here we are able, for the first time, to achieve a good fit to the Rosetta data by parameterizing EAF in terms of the different geological unit types on 67P (Fig. 1). This may have important implications for understanding how activity works on the different types of surface observed on cometary nuclei, including ‘rough’, ‘smooth’, ‘dusty’ and ‘rocky’ surface morphologies. Finally, in addition to the changes in rotation period examined in [2], we also compute changes in the rotation axis in order to compare with the observations.References
Morphology of an arid landscape utilising synthetic-aperture radar (SAR) and differential interferometric SAR (DInSAR), southern Riyadh, Central Arabia
Authors: Daoudi Mohamed , Hachemi Kamel , Bamousa Abdullah O.
Published: October 2020

Abstract. This study on the southern Riyadh area examines the ERS-1/2 and ENVISAT satellites data' ability of detecting Early Quaternary-Holocene trans-tensional Central Arabian graben system morphology. It also, test the hypothesis of potentially geohazardous arid region for the consequent dissolution-induced collapses and karstifications and possible recent faults reactivation. Eight Single Look Complex (SLC) amplitude images are calibrated, filtered, georeferenced, orthorectified, and filtered at a resolution of 20 metres, and compared with one another by producing 17 diachronic images of the pairs at different intervals (1996, 2003–2005, 2008). The diachronic SAR intensity imageries suggest a downthrown displacement reaching 600 m and eastward tilting at the bottoms of the grabens. Also, the structurally-controlled valleys are developing an eastward-running drainage system towards the oasis of Al-Kharj and capturing an older hydrologic system. Moreover, a 12-year period (1996–2008) of the SAR data was obtained to examine the average annual rate of southern Riyadh's anthropological sprawl, which is estimated at approximately 390 metres/year over the 12 years and constrained by geomorphological features towards the deformed area. DInSAR imageries show the primary results obtained from the 26 May 2004 and 31 Jan. 2005 pair of images, merged with 30 m resolution DEM-SRTM data for the arid region south of Riyadh to eliminate the influence of topography. DInSAR is applied in this study for its ability of detecting small displacements at the centimetre scale (1/2 wavelength). Although the DInSAR's coherence and phase imageries suggest a fairly stable region since the last tectonic and subsequent geomorphic events, erosional and artificial changes are observed, bounded within the valleys and depressions, primarily due to aeolian and fluvial processes and agriculture. It is highly recommended to preserve the area for sustainability and economy.
Desmocysta hadra, a new Late Cretaceous dinoflagellate cyst species: stratigraphic range, palaeogeographic distribution and palaeoecology
Authors: Vieira Manuel , Mahdi Salih
Published: October 2020

Abstract. A new species of dinoflagellate cyst, Desmocysta hadra sp. nov., is described from the early Campanian (Late Cretaceous) in the Norwegian Sea. This new taxon differs from the other three known species by its particularly robust but highly folded wall and the short, fine filaments arising from the antapex. The short stratigraphic range of early Campanian for this new species was calibrated with other regional well-dated dinoflagellate cysts, making it a good biostratigraphic marker. A review of the taxonomic description of the genus has also been undertaken using the available published data. The available data shows a consistent presence of Desmocysta in the fossil record from the Early Cretaceous to the late Paleocene, although some Late Jurassic occurrences have been reported in the North Sea Basin. The current records also indicate that this genus is restricted to higher latitudes in the Northern Hemisphere. Based on Paleocene and Late Cretaceous occurrences of the genus, and its association with dinoflagellate cysts, prasinophytes and acritarchs, a proximal, highly stressed marine environment for Desmocysta is suggested.
Exploring the potential relationship between the occurrence
of debris flow and landslide
Authors: Liang Zhu , Wang Changming , Ma Donghe , Ullah Jan Khan Kaleem
Published: October 2020

Abstract. he aim of the present study is to explore the potential relationship between debris flow and soil slide by establishing susceptibility zoning maps (SZM) separately with the use of random forest. Longzi County, located in Southeastern Tibet, where historical landslides occurred commonly, was selected as the study area. The work has been carried out with the following steps: (1) An inventory map consisting of 448 landslides (399 soil slides and 49 debris flows) was determined; (2) Slope units and 11 conditioning factors were prepared for the susceptibility modelling of landslide while watershed units and 12 factors for debris flow; (3) SZM were constructed for landslide and debris flow, respectively, with the use of random forest; (4) The performance of two models were evaluated by 5-fold cross-validation using relative operating characteristic curve (ROC), area under the curve (AUC) and statistical measures; (5) The potential relationship between soil slide and debris flow was explored by the superimposition of two zoning maps; (6) Gini index was applied to determined the major factors and analyze the difference between debris flow and soil slide; (7) A combined susceptibility map with two kinds of disaster was obtained. Two models had demonstrated great predictive capabilities, of which accuracy and AUC was 87.33 %, 0.902 and 85.17 %, 0.892, respectively. The loose sources need by the debris flow were not necessarily brought by the landslides although most landslides can be converted into debris flow. The area prone to debris flow did not promote the occurrence of landslide. A susceptibility zoning map composed of two or more natural disasters is comprehensive and significant in this regard, which provides valuable reference for researches of disaster-chain and engineering applications.
Synoptic atmospheric circulation patterns associated with deep
persistent slab avalanches in the western United States
Authors: Schauer Andrew R. , Hendrikx Jordy , Birkeland Karl W. , Mock Cary J.
Published: October 2020

Abstract. Deep persistent slab avalanches are capable of destroying infrastructure and are usually unsurvivable to those who are caught. Formation of a snowpack conducive to deep persistent slab avalanches is typically driven by meteorological conditions occurring in the beginning weeks to months of the winter season, and yet the avalanche event may not occur for several weeks to months later. While predicting the exact timing of the release of deep persistent slab avalanches is difficult, onset of avalanche activity is commonly preceded by rapid warming, heavy precipitation, or high winds. This work investigates the synoptic drivers of deep persistent slab avalanches at three sites in the Western USA with long records: Bridger Bowl, Montana; Jackson, Wyoming; and Mammoth Mountain, California. We use self-organizing maps to generate twenty synoptic types that summarize 5,899 daily 500 mb geopotential height maps for the winters (November–March) of 1979/80–2017/18. For each of the three locations, we identify major and minor deep persistent slab avalanche seasons, and analyze the number of days represented by each synoptic type during the beginning (November–January) of the major and minor seasons. We also examine the number of days assigned to each synoptic type during the 72 hours preceding deep persistent slab avalanche activity for both dry and wet slab events. Each of the three sites exhibits a unique distribution of the number of days assigned to each synoptic type during November–January of major and minor seasons, and for the 72-hour period preceding deep persistent slab avalanche activity. This work identifies the synoptic scale atmospheric circulation patterns contributing to deep persistent slab instabilities, and the patterns that commonly precede deep persistent slab avalanche activity. By identifying these patterns, we provide an improved understanding of deep persistent slab avalanches, and an additional tool to anticipate the timing of these difficult-to-predict events.
Kinematics and extent of the Piemont-Liguria Basin – implications for subduction processes in the Alps
Authors: Le Breton Eline , Brune Sascha , Ustaszewski Kamil , Zahirovic Sabin , Seton Maria , Müller R. Dietmar
Published: October 2020

Abstract. Assessing the size of a former ocean, of which only remnants are found in mountain belts, is challenging but crucial to understand subduction and exhumation processes. Here we present new constraints on the opening and width of the Piemont-Liguria (PL) Ocean, known as the Alpine Tethys together with the Valais Basin. We use a regional tectonic reconstruction of the Western Mediterranean-Alpine area, implemented into a global plate motion model with lithospheric deformation, and 2D thermo-mechanical modelling of the rifting phase to test our kinematic reconstructions for geodynamic consistency. Our model fits well with independent datasets (i.e. ages of syn-rift sediments, rift-related fault activity and mafic rocks) and shows that the PL Basin opened in four stages: (1) Rifting of the proximal continental margin in Early Jurassic (200–180 Ma), (2) Hyper-extension of the distal margin in Early-Middle Jurassic (180–165 Ma), (3) Ocean-Continent Transition (OCT) formation with mantle exhumation and MORB-type magmatism in Middle-Late Jurassic (165–154 Ma), (4) Break-up and mature oceanic spreading mostly in Late Jurassic (154–145 Ma). Spreading was slow to ultra-slow (max. 22 mm/yr, full rate) and decreased to ~ 5 mm/yr after 145 Ma while completely ceasing at about 130 Ma due to motion of Iberia relative to Europe during the opening of the North Atlantic. The final width of the PL Ocean reached a maximum of 250 km along a NW–SE transect between Europe and Adria (Ivrea). In the Cretaceous and Cenozoic, the amount of plate convergence between Adria (Ivrea) and Europe during Alpine subduction (84–35 Ma, 420 km) and collision (35–0 Ma, 260 km) largely exceeded the width of the ocean. We suggest that at least 63 % of the subducted and accreted material was highly thinned continental lithosphere and most of the Alpine Tethys Ophiolites exhumed today derived from OCT zones. Our work highlights the importance of distal rifted continental margins during subduction and exhumation processes and provides quantitative estimates for future geodynamic modelling and a better understanding of the Alpine Orogeny.