bluuebunny/crossref_metadata_2025 huggingface dataset:
Calibration and evaluation of broad supersaturation scanning (BS2) cloud condensation nuclei counter for rapid measurement of particle hygroscopicity and CCN activity
Authors: Kim Najin , Cheng Yafang , Ma Nan , Pöhlker Mira L. , Klimach Thomas , Mentel Thomas F. , Krüger Ovid O. , Pöschl Ulrich , Su Hang
Published: July 2021

Abstract. For understanding and assessing aerosol-cloud interactions and their impact on climate, reliable measurement data of aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in CCN measurements. Compared to the existing differential mobility analyzer (DMA)-CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure the CCN activity with a high time-resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (Saerosol) and the activated fraction (Fact) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly. Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (Fact – Saerosol). For calibration, size-resolved CCN measurements with ammonium sulfate and sodium chloride particles are performed under the three different thermal gradient (dT) conditions (dT = 6, 8, and 10 K). We point out key processes that can affect the calibration curve and thereby need to be considered as follows: First, the shape of the calibration curve is primarily influenced by Smax, the maximum S in the activation tube. We need to determine appropriate Smax depending on particle size and κ to be investigated. To minimize the effect of multiply charged particles, small geometric mean diameter (𝐷𝑔) and 𝜎𝑔 geometric standard deviation (𝜎𝑔) in number size distribution are recommended when generating the calibration aerosols. Last, Fact is affected by particle number concentration and has a decreasing rate of 0.02/100 cm−3 due to the water consumption in the activation tube. For evaluating the BS2-CCN system, inter-comparison experiments between typical DMA-CCN and BS2-CCN measurement were performed with the laboratory-generated aerosol mixture and ambient aerosols. Good agreements of κ values between DMA-CCN and BS2-CCN measurements for both experiments show that the BS2-CCN system can measure CCN activity well compared to the existing measurement, and can measure a broad range of hygroscopicity distribution with a high time-resolution (~1 second vs. few minutes for a standard CCN activity measurement). As the hygroscopicity can be used as a proxy for the chemical composition, our method can also serve as a complementary approach for fast and size-resolved detection/estimation of aerosol chemical composition.
Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS)
Authors: Bolin Bryce , Fernandez Yanga , Lisse Carey , Holt Timothy
Published: July 2021

We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μm-scale dust ejected at ∼1m s−1 speeds with a ∼1'' jet pointing in the southwest direction. LD2 experienced a total dust mass loss of ∼108 kg at a loss rate of ∼6 kg s−1 with Afρ/ cross-section varying between ∼85 cm/125 km2 and ∼200 cm/310 km2 from 2019 April 9 to 2019 November 8. If the increase in Afρ/cross section remained constant, it implies LD2ʼs activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of
The discovery and characterization of 2020 AV2, the first known asteroid in the class of inner-Venus asteroids
Authors: Bolin Bryce T. , Ip Wing-Huen , Masci Frank J. , Helou George
Published: July 2021

Near-Earth asteroid population models predict a small population of asteroids located entirely within the orbit of Venus. We report the discovery of the first inner-Venus asteroid (IVA), 2020 AV2, was first detected by the Zwicky Transient Facility (ZTF) on the Samuel Oschin Telescope 48-inch telescope at Palomar Observatory on 2020 January 4. Recovery observations by the Spectral Energy Distribution Machine on the Palomar 60-inch Telescope and the Lulin Optical Telescope at Lulin Observatory in late 2021 November greatly extended its orbit to ~330 days confirm its location inside the orbit of Venus and allowing for detail investigation of its dynamical evolution. In addition, a comparison with the NEO model reveals its likely source location in agreement with recent spectroscopic observations. In addition, we provide an estimate of our observational completeness for detecting inner-Venus asteroids with ZTF with implications on the expected number of their detection.
Planetesimal formation by the “no-drift” mechanism
Authors: Hyodo Ryuki , Ida Shigeru , Guillot Tristan
Published: July 2021

A notable challenge of planet formation is to find a path to directly form planetesimals from small particles. Small particles are, in general, challenged to grow beyond meter size due to the “growth barrier” and the “drift barrier”.Over the last few decades, magnetohydrodynamic (MHD) simulations have shown that a region where ionization is too low for the magneto-rotational instability (MRI) to operate (i.e., a “dead zone”) might ubiquitously exist in the inner part of the disk midplane, and that only surface layers are magnetically active, supporting accretion. These indicate a nonuniform turbulence structure.In this study, we aim to understand how drifting pebbles pile up in a protoplanetary disk with a nonuniform turbulence structure (Figure 1). We consider a disk structure in which the midplane turbulence viscosity (i.e., diffusion of pebbles is characterized by a distinct non-dimensional parameter (αmid)) increases with the radius in protoplanetary disks, such as in the outer region of a dead zone. We consider that the gas accretion toward the central star is characterized by a distinct non-dimensional parameter (αacc). We perform 1D diffusion-advection simulations of pebbles that include back-reaction (the inertia) to the radial drift and the vertical and radial diffusions of pebbles for a given pebble-to-gas mass flux (Fp/g).We report a new mechanism, the “no-drift” runaway pile-up (i.e., instability), that leads to a runaway accumulation of pebbles in disks, thus favoring the formation of planetesimals by streaming and/or gravitational instabilities. This occurs when pebbles drifting in from the outer disk and entering a dead zone experience a decrease in vertical turbulence. Consequently, the scale height of the pebble then decreases, and, for small enough values of the turbulence in the dead zone and high values of the pebble-to-gas flux ratio, the back-reaction of pebbles on gas leads to a significant decrease in their drift velocity and thus their non-steady-state accumulation (i.e., a local runaway pile-up of pebbles). This process is independent of the existence of a pressure bump and/or pebble growth. Figure 1: Schematic illustration of pebble drift and its pile-up within a protoplanetary disk with a dead zone. The disk gas accretion is characterized by alpha-parameter (αacc), while the midplane diffusivity, being a dead zone (αdead
Modulation of ion escape by ultra-low frequency waves at Venus and Mars in a global hybrid simulation
Authors: Jarvinen Riku , Kallio Esa , Pulkkinen Tuija
Published: July 2021

We investigate the effect of foreshock ultra-low frequency (ULF) waves on the solar wind induced heavy ion escape from Venus and Mars in a global hybrid model. The foreshock ULF waves are excited by backstreaming ion populations scattered at the quasi-parallel bow shock, and convect downstream with the solar wind. In the model, the waves affect magnetic and electric fields in the Venusian and Martian plasma environments causing fluctuations in the heavy ion acceleration processes such as the solar wind ion pickup. This leads to significant modulations in global escape rates of ionized planetary volatiles at the ULF wave frequency. We study this process in a global hybrid model, where ions are treated as particle clouds moving under the Lorentz force and electrons are a charge-neutralizing fluid. The analyzed simulation runs use more than 200 simulation particle clouds per cell on average to allow enough velocity space resolution for resolving foreshock, wave phenomena and ion escape processes self-consistently. We find that at Venus the global ion escape is modulated by the ULF waves even under nominal solar wind and IMF upstream conditions, while at Mars the modulation becomes significant under a strongly radial IMF orientation.
Hubble Space Telescope detects sub-solar water atmosphere on Ganymede
Authors: Roth Lorenz , Ivchenko Nickolay , Gladstone Randy , Saur Joachim , Grodent Denis , Bonfond Bertrand , Molyneux Philippa , Retherford Kurt
Published: July 2021

Ganymede’s tenuous atmosphere is produced by charged particle sputtering and sublimation of its icy surface. Previous far-ultraviolet observations of the OI1356 Å and OI1304 Å oxygen emissions were used to derive sputtered molecular oxygen, O2, as an atmospheric constituent. We present a new analysis of high-sensitivity spectra and spectral images of Ganymede’s oxygen emissions acquired by the COS and STIS instruments on the Hubble Space Telescope. The COS eclipse observations constrain atomic oxygen, O, to be at least two orders of magnitude less abundant than O2. We then show that dissociative excitation of water vapor, H2O, is found to increase the OI1304 Å emissions relative to the OI1356 Å emissions around the sub-solar point, where H2O is more abundant than O2. Away from the sub-solar region, the emissions are more than two times brighter at OI1356 Å than at OI1304 Å, and O2 prevails as found in previous analyses. A ~6-fold higher H2O/O2 mixing ratio on the warmer trailing hemisphere compared to the colder leading hemisphere, a spatial concentration at the sub-solar region, and the ratio-estimated H2O densities identify icy surface sublimation as a local dayside atmospheric source.Our analysis provides the first evidence for a sublimated atmosphere on an icy moon in the outer solar system.
Carbonaceous Chondrite Outgassing Experiments: Implications for Methane Replenishment on Titan
Authors: Yu Xinting , Thompson Maggie , Duncan Taylor , Kim Kyle , Telus Myriam , Zhang Xi , Joshi Toyanath , Lederman David
Published: July 2021

Titan is the only known moon in the Solar System with a substantial atmosphere of N2 and CH4. However, its origin and evolution are not well understood. Titan’s present amount of atmospheric CH4 was predicted to be destroyed photochemically on very short timescales (~ 10 Myrs, Yung et al. 1984). This suggests that a methane resupply mechanism is necessary. The Huygens probe GCMS measurements of noble gases suggest that Titan’s atmosphere is likely linked to its interior instead of being incorporated during formation (Nieman et al., 2005). Recent theoretical modeling works of Titan’s atmosphere and interior suggest that its atmosphere could have originated partly by outgassing primordial organics in its interior (Neri et al. 2019; Miller et al. 2019). If this theory holds, volatiles like methane could be outgassing from Titan’s interior to sustain its current observed abundances. Insoluble organic matter (IOM) found in carbonaceous chondrites may serve as an analog for the organic material in Titan’s interior and provide experimental constraints on the outgassed component of its atmosphere (Thompson et al. 2021). By heating carbonaceous chondrite samples and measuring the abundances of their released volatiles, specifically methane, we may be able to connect what we see in the lab to species in Titan’s atmosphere today.We performed outgassing experiments using three primordial CM carbonaceous chondrites: Murchison, Aguas Zarcas, and Jbilet Winselwan. The first two are "fall" meteorite (1969 and 2019), and Jbilet Winselwan is a desert "find'' meteorite (2013). We used two sizes of samples for each CM chondrite for the measurements: a small grain sample with diameters < 20 µm and a normal grain sample with diameters of 20-100µm. Each sample underwent a step heating scheme where they are heated and held at every 100°C from room temperature to 1200° C. The whole heating scheme takes 12 hours. We continuously monitored the partial pressures of 10 outgassed mass peaks using a residual gas analyzer (RGA).We can estimate how much methane can be outgassed from the insoluble organics in the CM chondrites with the RGA data. We found that chondrite outgassing can resupply methane that can last for ~0.5-2 Gyrs. If organics indeed makes a significant fraction of Titan's interior, outgassing through thermal instability of Titan's interior can potentially resupply Titan's atmospheric methane for a period of time.
HST WFC3 G141 data analysis: exploring the transition from Super-Earth to Sub-Neptune
Authors: Gressier Amélie , Marcq Emmanuel , Beaulieu Jean-Philippe , Charnay Benjamin
Published: July 2021

Exoplanets with size between the Earth and Neptune (1-4R⊕) do not have any equivalent in our Solar System and remain challenging to characterize. Yet, there are ubiquitous in the Galaxy and Fulton et al. (2017) showed that their distribution (number of planets per star vs radius) is bimodal highlighting a gap in the number of planets around 1.7R⊕. Planets with a radius below 1.7R⊕ are thought to be mostly rocky planets, and called Super-Earth, above this limit planets are most likely made of gas and called Sub-Neptune. We made use of the available data from the Hubble Space Telescope in Near-Infrared (HST WFC3 G141) and gathered 18 transmission spectra of planets with size below 6 R⊕ to study the transition between rocky and gaseous planets. First, we used TauREx3 (Al-Refaie et al. 2019), a Bayesian retrieval code, to rule out atmospheric scenarios. We proved that a primary clear atmosphere dominated by Hydrogen and Helium is rejected with more than 3σ for a large majority of planets in the sample. Then, we measured the amplitude of the spectra in the water absorption band (around 1.4μm) and compared observational values to simulated ones using a self-consistent modeling code ExoREM (Baudino et al. 2015; Charnay et al. 2018). We explored the connection between the water absorption amplitudes and the temperature by setting the stellar and planetary parameters to those of HD 3167 c (2.7 R⊕, 8.33 M⊕) and trying different metallicities (1, 10, 100 and 1000 x solar), cloud compositions and temperatures (300-1200K).
Formation timescale model for a small sized Martian fluvial valley
Authors: Steinmann Vilmos , Kereszturi Ákos
Published: July 2021

Most of the Martian fluvial valleys formed in the early period (around the Noachian-Hesperian boundary or before), but the formation durations are not well determined, however it would be important to understand as it is related to the climatic history and the reason for specific morphology of the Red Planet’s valleys. We estimated the formation duration for a hundred different sections of a small (~81 km long) Martian valley (called Tinto B, which is East of Palos crater and Tinro Vallis), using ArcMap and Excel software. We used the HRSC DTM (Digital Terrain Model), which was resampled from the resolution of 50 m/px to 100 m/px, because the used THEMIS TI dataset (used for grain size estimation) has a 100 m/px resolution. The visual morphological analysis we used the CTX images.  For the calculation we considered the cross-sectional profile of the valley as a trapezoid shape and calculated the hydraulic radius for it and used several hydraulic variables, like average flow velocity, bedload transport rate, sediment and flow discharge [1], slope of energy grade line. For the formation timescale calculation the Meyer-Peter and Muller bedload transport equation [2] was used. For the sediment grain size estimation we used the THEMIS TI dataset and calculated the shear stress and the Shield parameter from it [3]. The bed of the valley is covered with aeolic sand, which does not represent the grain size of the eroded bedrock, which probably took part in the original formation process. For this reason we sampled the grain size from exposures on both sides of the valley walls, where the original bedrock represented to the best approximation and continuously. The main aim of the work is to compare the different sections of the analysed valley by the final assumed age and different variables and morphology. The detailed morphology analísation comes from the previously made erosion-accumulation results [4] and the visual analysis of the valley. From the given section results the median formation time scale of the valley can be calculated also. With this method the Martian valleys can be comparable with the terrestrial mars-analog valleys after the same calculations. The estimated formation timescale of the whole valley will be compared with the result of the crater size frequency distribution based statistically estimated age of the valley bed.  References:[1] - M. R.T. Hoke, B. M. Hynek, G. E. Tucker, Formation timescales of large Martian valley networks, Earth and Planetary Science Letters, 2011, Volume 312, Issues 1–2[2] - M. Wong, G. Parker, Reanalysis and correction of bed-load relation of Meyer-Peter and Muller using their own database, J. Hyrdaul. Eng, 2006, pp. 1159-1168[3] - L. K. Fenton, J. L. Bandfield, A. W. Ward, Aeolian process on Mars: atmospheric modeling and GIS analysis, Journal of Geophysical Research, 2003[4] - V. Steinmann, Á. Kereszturi, L. Mari, Geomorphological analysis of Tinto-B Vallis on Mars, Hungarian Geographical Bulletin, 2020, pp 333-348
Laboratory investigations of the electromagnetic properties of a powdered L-chondrite
Authors: Brin Alessandro , Lauro Sebastian , Cosciotti Barbara , Mattei Elisabetta , Pettinelli Elena
Published: July 2021

IntroductionRadio Echo Sounding (RES) has been employed in planetary missions to survey the Moon, Mars, and Comet 67P/Churyumov-Gerasimenko (Porcello et al., 1974; Plaut et al., 2007; Kofman et al., 2015) and it will be applied, among others, in future investigations of the Galilean moons (JUICE mission - Grasset et al., 2013; EUROPA CLIPPER mission – Blankenship et al., 2018), and asteroids (e.g. AIDA mission - Herique et al., 2019). The ability of a radar signal to penetrate and image the subsurface layers depends on both the dielectric permittivity and magnetic permeability of the materials composing the crust. Thus, laboratory experiments are essential to improve our capability to estimate the radar performance and interpret the radar data collected in different scenarios. We present here the results of the electromagnetic measurements conducted for different porosities of a powdered L5 chondrite sample (a good simulant of the surface of Ganymede and S type asteroids), in the frequency range of interest for planetary radar sounders (1 MHz-1 GHz).MethodologyThe analyzed meteorite was classified as an ordinary L5 chondrite, with shock grade S2 and weathering W2 (Cosciotti et al.,2021). A fragment of the solid meteorite was pulverized in a jaw crusher and then sieved, to obtain five different granulometric samples, from
Shape models and dynamical properties of basaltic asteroids outside the dynamical Vesta family
Authors: Troianskyi Volodymyr , Oszkiewicz Dagmara , Marciniak Anna , Kankiewicz Pawel , Fohring Dora , Galad Adrian , Kwiatkowski Tomasz , Skiff Brian A. , Geier Stefan , Wilawer Emil , Moskovitz Nicholas A. , Gajdos Stefan , Vilagi Jozef , Polcic L'udovit , Kashuba Volodymyr , Udovichenko Sergei , Keir Leonid , Kaminski Krzysztof , Benishek Vladimir , Polakis Tom
Published: July 2021

Through numerical modeling, Nesvorny et al. (2008) showed that asteroids can migrate due to Yarkovsky drift and resonances to outside of the boundaries of the Vesta family. In particular, they found that objects which end up in the scattered resonances region (so-called Cell I, defined by orbital elements 2.2 AU < a < 2.3 AU, 0.05 < e < 0.2, 0 < i deg < 10 deg) typically have retrograde rotations and thermal parameters that maximize Yarkovsky drift rates. These autors also showed, that asteroids migrating to the low inclination region (Cell II defined by 2.32 AU < a < 2.48 AU, 0.05 < e < 0.2, 2 deg < i < 6 deg) should be predominantly prograde rotators.We performe photometric observations and determine spins and shapes of V-type objects in Cell I and Cell II in order to characterize the dynamical properties of these asteroids more accurately. The results of dynamical modelling show that some asteroids may have migrated to their current location from the Vesta family within ~2 Gy. There are objects, however, whose origin in another parent body may also be plausible. This may support the hypothesis that the number of differentiated basaltic objects in the inner and middle Main Belt should be much higher than previously assumed. We will present preliminary results for the first ~10 asteroids in Cell I and Cell II.
Aeolian processes on Venus: Probabilistic study on threshold speeds
Authors: Bhattacharya Ananyo
Published: July 2021

Dust particles and haze formation on the surface of Venus have been observed and studied using several independent techniques onboard Venus lander missions. A possibility of mineral haze formation in highlands is supported by observations of high reflectivity and low emissivity features from Pioneer Venus Orbiter and Magellan radar experiments, while Venera 13 and 14 spectrophotometer analysis yields appreciable aerosol extinction at the same altitudes. In this work, we present threshold parameters for dust lifting from 1 μm to 1 cm sized dust particles over the globe using emissivity and surface topography data provided by Magellan radar. The threshold wind speeds have been derived using theoretical and experimental models and compared with the in-situ measurements reported earlier. Haze formation is less likely to occur solely due to wind shear by micron and submicron sized particles. The entrainment process and properties of the boundary layer also contribute to variation in threshold wind speeds and particle transport.
Dust distribution and dynamics in the coma of 67P/Churyumov-Gerasimenko
Authors: Lemos Pablo
Published: July 2021

In this work, the motion of dust particles in the coma of the comet 67P/Churyumov-Gerasimenko is investigated. This is done by analyzing sets of images taken by OSIRIS, the main imaging system on board Rosetta, in which these dust particles can be seen as bright tracks instead of points sources, as result of the combination of motions of both particles and spacecraft. A fundamental obstacle to deriving the dust size and velocity distribution from such data is that without additional information, the apparent brightness of a particle constrains only the ratio of size and distance, but neither quantity individually.While previous works in this area focused on obtaining the distance to individual detected particles in the image, a novel approach to analyze the dynamics of the dust is introduced in this work. This new approach is based on the statistical comparison between the images obtained by the camera, and synthetic images created by modeling the dynamics of the dust in the coma. The main advantage of this approach is to bypass the mentioned distance determination to the particles, which lifts the strict requirement on the observation conditions that were imposed by the earlier methods. This allows us to analyze a much larger set of images, and then, characterize the dust distribution and dynamics at the coma in a variety of conditions.Our method can be divided in three main parts. First, dust tracks on the OSIRIS images are detected using an algorithm based on the Hough transform method. Secondly, the trajectories of dust particles under the influence of gas drag, nucleus gravity, and solar radiation pressure are modeled. These trajectories vary depending on the dust properties, such as density and size. The combination of the trajectories and the information about spacecraft position and orientation allows us to generate synthetic images for each type of modeled dust. Lastly, the distribution of selected track properties, like orientation, length and total brightness, obtained from the real images, is fitted by combining the ones obtained from the synthetic images. This allows us to estimate the contents of each type of dust in the coma. 
Modeling the structure of irradiated ocean planets - implications for mass-radius relationships
Authors: Aguichine Artyom , Mousis Olivier , Deleuil Magali , Marcq Emmanuel
Published: July 2021

Water-rich planets should be ubiquitous in the universe. Among the current exoplanet populations, many of those worlds are subject to important irradiation from their host star. As a consequence, water-rich worlds display supercritical water layer surrounded by an extended steam atmosphere making them good candidates for matching the observed mass-radius distribution of sub-Neptunes [1]. Here we describe a model that computes a realistic structure for water-rich planets by combining an interior model with an updated equation of state (EoS) for water, and an atmospheric model that takes into account radiative transfer. Our model has been applied to the GJ 9827 system as a test case and indicates Earth- or Venus-like interiors for planets b and c, respectively. Planet d could be an irradiated ocean planet with a water mass fraction of ∼20 ± 10%. We also provide mass-radius relationships for water-rich planets and their analytical expression. This allows one to directly retrieve a wide range of planetary compositions, without the requirement to run the model. The possible existence of such planets is discussed in light of atmospheric loss processes, suggesting that some sub-Neptunes are the outcome of planets that lost their H/He reservoirs.

Figure 1. Mass-radius relationships produced by our model (green, yellow and red thick lines) [2], compared to mass-radius relationships of planets with only condensed phases and no atmosphere (black, grey and light blue thin lines) [3,4]. A few planets of the solar system, the GJ-9827 system and the TOI-178 system are shown as well [5,6].
[1] Mousis, O., Deleuil, M., Aguichine, A., et al. 2020, ApJL, 896, L22.[2] Aguichine, A., Mousis, O., Deleuil, M., et al. 2021, accepted in ApJ.[3] Zeng, L., Sasselov, D. D., & Jacobsen, S. B. 2016, ApJ, 819, 127.[4] Brugger, B., Mousis, O., Deleuil, M., et al. 2017, ApJ, 850, 93.[5] Kosiarek, M. R., Berardo, D. A., Crossfield, I. J. M., et al. 2021, AJ, 161, 47.[6] Leleu, A., Alibert, Y., Hara, N. C., et al. 2021, A&A, 649, A26.
Trajectory and dark-flight estimation for meteoroids detected by the MOROI network
Authors: Boaca Ioana Lucia , Nedelcu Alin , Birlan Mirel , Boaca Tudor , Anghel Simon
Published: July 2021

The Romanian all-sky network Meteorites Orbits Reconstruction by Optical Imaging (MOROI) was deployed in 2017 [3] and it is fully compatible with the FRIPON one [2]. In 2020 we started to integrate the MOROI database into the FRIPON one. Figure 1 presents the statistics of the weekly multiple events (detected by two or more cameras) for 2017-2019. Figure 2 presents the preliminary statistics of number of meteors vs. duration of luminous phenomenon for 2017-2020. Nowadays the MOROI network consists of 16 all-sky cameras (to be extended to 24).In [1] is presented a mathematical model for the dark-flight trajectory of a meteoroid based on the influence of the wind, the properties of the atmosphere, the Coriolis force and the centrifugal force. This model uses the ellipsoid shape of the Earth instead of the classical spherical one and a stochastic analysis of meteoroids inside a range of velocities using a Gaussian distribution.In this paper we present some of the detections from the MOROI network. We present their luminous trajectory and we apply the dark-flight model from [1] in order to obtain their strewn field.   
  
  
                                                                 Figure 1: Number of weekly events for 2017-2019                                                                                                                        Figure 2: Distribution of duration of meteors for 2017-2020 Acknowledgements:This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0784, within PNCDI III.References:[1] Boaca I., Nedelcu A., Birlan M., Boaca T., Anghel S. Mathematical model for the dark-flight trajectory of a meteoroid, submitted to Romanian Astronomical Journal.[2] Colas F., Zanda B., Bouley S., Jeanne S., Malgoyre A., Birlan M., Blanpain C., Gattacceca J., Jorda L., Lecubin J., et al. (385 more) FRIPON: a worldwide network to track incoming meteoroids. Astronomy &. Astrophys. 644, A53. doi:10.1051/0004-6361/202038649. 2020.[3] Nedelcu D.A., Birlan M., Turcu V., Boaca I., Badescu O., Gornea A., Sonka A.B., Blagoi O., Danescu C., Paraschiv P. Meteorites Orbits Reconstruction by Optical Imaging (MOROI) Network. Romanian Astronomical Journal 28(1), 57 – 65. 2018. 
Investigating global scale dust storms on Mars with ASPERA-3
Authors: Regan Catherine , Coates Andrew , Jones Geraint , Wellbrock Anne , Holmstrom Mats , Frahm Rudy
Published: July 2021

2007 and 2018 saw global scale dust storms engulfing the entirety of Mars, lasting several months. These events have a profound impact across Mars, with dust reaching altitudes up to 80 km and global temperatures rising by up to 40 K. This significant change in the Martian atmosphere may lead to changes in the ionosphere and above. During the 2007 storm, it was seen in Mars Express (MEx) radar data that ionisation created in the lower atmosphere is observed at higher altitudes, with an altitude dependent enhancement in plasma density over crustal magnetic fields (Venkateswara et al., 2019). It may be likely that during these dust events, atmosphere loss is enhanced.MEx launched in 2003, became operational in 2004 and is still collecting data today. Onboard are seven scientific instruments which are answering questions about the atmosphere, surface and geology at Mars, whilst looking for signs of water and life. With a period of seven hours, MEx provides extensive coverage of data collection. One of the seven instruments, the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) has produced a long time-base of plasma measurements from as low as 250 km. ASPERA-3 aims to investigate the interaction of the solar wind with the Martian atmosphere, looking at the mechanisms that may enhance the loss of gases from Mars.ASPERA-3 will be used to investigate the effects the 2007 and 2018 global dust storms had on the plasma environment by comparing data before, during, and after the event.  Of particular interest are plasma measurements over radial magnetic fields from crustal anomalies, where transport of charged particles is guided out of the atmosphere.  The before, during, and after effects will shed light on to the influence dust storms have on the escaping plasma measured by ASPERA-3 and how dust changes the local plasma escape directly from the atmosphere. Our initial study focuses on data from the electron spectrometer (ELS) where we investigate how the energy distribution and peak energy value varies in altitude above the Martian surface. We will also relate our observations back down to the Martian surface, where we will investigate how surface features may influence the atmosphere and ionosphere above them. This will focus on the southern hemispheric crustal fields and geological features, such as impact basins and volcanoes.
Direct imaging of sub-Jupiter mass exoplanets with James Webb Space Telescope coronagraphy
Authors: Carter Aarynn
Published: July 2021

The James Webb Space Telescope (JWST), currently scheduled to launch in 2021, will dramatically advance our understanding of exoplanetary systems with its ability to directly image and characterise planetary-mass companions at wide separations through coronagraphy. Using state-of-the-art simulations of JWST performance, in combination with the latest evolutionary models, we present the most sophisticated simulated mass sensitivity limits of JWST coronagraphy to date. In particular, we focus our efforts towards observations of members within the nearby young moving groups 𝛽 Pictoris and TW Hya. These limits indicate that whilst JWST will provide little improvement towards imaging exoplanets at short separations, at wide separations the increase in sensitivity is dramatic. We predict JWST will be capable of imaging sub-Jupiter mass objects beyond ∼30 au, sub-Saturn mass objects beyond ∼50 au, and that beyond ∼100 au, JWST will be capable of directly imaging companions as small as 0.1 𝑀J − at least an order of magnitude improvement over the leading ground-based instruments. Probing this unexplored parameter space will be of immediate value to modelling efforts focused on planetary formation and population synthesis. JWST will also serve as an excellent complement to ground based observatories through its unique ability to characterise previously detected companions across the near- to mid-infrared for the first time.
Statistics on Jupiter's Current Sheet with Juno Data: Geometry, Magnetic Fields and Energetic Particles
Authors: Liu Zhi-Yang , Zong Qiu-Gang , Blanc Michel
Published: July 2021

Jupiter's magnetosphere contains a current sheet of huge size near its equator. The current sheet not only mediates the global mass and energy cycles of Jupiter's magnetosphere, but also provides an occurring place for many localized dynamic processes, such as reconnection and wave-particle interaction. To correctly evaluate its role in these processes, a statistical description of the current sheet is required. To this end, here we conduct statistics on Jupiter's current sheet, with four-year Juno data recorded in the 20-100 Jupiter radii, post-midnight magnetosphere. The results suggest a thin current sheet whose thickness is comparable with the gyro-radius of dominant ions. Magnetic fields in the current sheet decrease in power-law with increasing radial distances. At fixed energy, the flux of electrons and protons increases with decreasing radial distances. On the other hand, at fixed radial distances, the flux decreases in power-law with increasing energy. The flux also varies with the distances to the current sheet center. The corresponding relationship can be well described by Gaussian functions peaking at the current sheet center. In addition, the statistics show the flux of oxygen- and sulfur-group ions is comparable with the flux of protons at the same energy and radial distances, indicating the non-negligible effects of heavy ions on current sheet dynamics. From these results, a statistical model of Jupiter's current sheet is constructed, which provides us with a start point of understanding the dynamics of the whole Jupiter's magnetosphere.
Polarimetric properties of asteroids in the near-infrared
Authors: Masiero Joseph , Muinonen Karri , Tinyanont Samaporn , Millar-Blanchaer Maxwell
Published: July 2021

We present first results from a polarimetric survey of asteroids in the near-infrared J and H bands (1.25 and 1.65 microns, respectively). This survey has been enabled by the newly commissioned WIRC-Pol instrument on the Palomar 5 m telescope.  WIRC-Pol simultaneously senses the four linear polarization components from the target, while using a half-wave plate to beam swap between them. This setup allows us to obtain bandpass polarimetric accuracies better than 0.1% for our targets.  WIRC-Pol also obtains low resolution spectra of each Stokes component, allowing us to investigate the spectropolarimetric properties of our targets as a function of phase.  We show polarimetric phase curves for objects that have been sampled at multiple phases, our initial spectropolarimetric findings, and discuss the results from modeling these observations. 
Evolution of the biases in retrieved atmospheric composition of hot Jupiters
Authors: Pluriel William , Leconte Jérémy , Zingalès Tiziano , Falco Aurélien , Parmentier Vivien
Published: July 2021

Transmission spectroscopy provides us with information on the atmospheric properties at the limb, which is often intuitively assumed to be a narrow annulus around the planet. This is why all existing retrieval algorithms used so far to constrain the atmospheric composition from data rely either on i) a single 1D forward model, thus assuming a uniform limb or ii) a linear combination of 1D models to account for heterogeneities between different regions of the limb (e.g. east vs. west). Even full three-dimensional atmospheric models (GCMs) commonly use only the atmosphericcolumns at the terminator to predict the observable transmission spectrum for a given simulation.Here, we will present numerical experiment from hot Jupiters to ultra hot Jupiters which demonstrate that the region probed in transmission actually extends significantly toward the day and night sides of the planet and that, as a result, the real transmission spectrum computed from a GCM simulation with our fully 3D radiative transfer differs significantly from results obtained with the usual assumptions, especially for the hottest atmospheres. This comes from the fact that the terminator of hot, synchronously rotating planets is a region exhibiting sharp thermal and compositional gradients.Fig 1: Sum up of the different geometry required in retrievals code to avoid biases according to the equilibrium temperature ofthe planet and the presence or the absence of optical absorber. 1D retrieval model appears to be correct for planets with equilibrium temperature lower than 1400 K when optical absorber (such as TiO, VO, Na, K, etc) are present in the atmosphere. They are howeverbiased above this limit where 2D retrieval code are mandatory.Using realistic hot exo-atmospheres from GCM model SPARC/MIT, we will demonstrate how this effect can lead to strong biases is the temperature and abundances retrieved from actual data biases that will need to be addressed and corrected for if we want to be able to make robust inferences from future JWST and ARIEL data. We will determine a global limit where the biases due the 1D hypothesis of retrieval model start to be negligible. We have also established a hierarchy of the different 3D effects (vertical, horizontal along and/or across the limb) in order to be able to chosse the right tool to break down the biases (see Fig. 1).  We will finally present our new tool, a 2D version of TauREx, which is designed to unravel these biases.
Modeling the global water cycle on Mars with improved physical parametrization
Authors: Naar Joseph , Forget Francois , Vals Margaux , Millour Ehouarn , Bierjon Antoine , González-Galindo Francisco , Richard Brunehilde
Published: July 2021

Introduction: For many years we have been working on the modeling of the martian water cycle in the Laboratoire de Météorologie Dynamique martian Global Climate Model [1,2,3,4]. This has been challenging because of destabilizing feedbacks such as the coupling between temperatures, water vapour, clouds, and temperature changes induced by radiatively active water clouds [2].It is interesting to accurately model Mars’s water cycle not only to understand present day Mars but also to simulate past climate changes induced by obliquity and orbital variations. This study is partly motivated by the ERC Mars Through Time project which notably aims at modeling recent (
Spatial characterization of the trailing and leading limbs of WASP-76b: Detection of H2O and HCN at high-resolution
Authors: Sánchez López Alejandro , Landman Rico , Casasayas Barris Núria , Kesseli Aurora , Snellen Ignas
Published: July 2021

Extreme temperature contrasts between the day and nightside of ultra-hot Jupiters (UHJ) result in significantly asymmetric atmospheres, with a region of extreme atmospheric expansion appearing over a small range of latitudes around the terminator. Over the course of a transit, WASP-76 b rotates by about 30° and hence temporal variations of the observable atmosphere could significantly affect the detectability of its constituents. Specifically, the trailing limb of this planet allows us to probe a significant portion of the inflated dayside, resulting in a higher atmospheric detectability. This geometric effect could mimic the observed time-variability of absorption signals due to condensation in the nightside of these planets, which has been recently reported for neutral iron in WASP-76 b. By studying molecules that are not expected to condense in the nightside of UHJs (~1000K), we can isolate the possible effect of different day and nightside scale heights. Here, we will analyze a stronger water vapor signal during the egress of the planet than at ingress, which cannot be explained by condensation and suggests that the extreme geometry of UHJ manifests itself as time-dependent absorption signals. Additionally, we report a redshifted HCN signature arising from the leading limb (i.e., observable in the first half of the transit and absent from the second half) and a weak evidence of ammonia using high-resolution observations of WASP-76 b with CARMENES.
Hayabusa2 Returned Samples: First Results From the MicrOmega Investigation Within the ISAS Curation Facility
Authors: Riu Lucie , Brunetto Rosario , Carter John , Gondet Brigitte , Hamm Vincent , Hatakeda Kentaro , Langevin Yves , Lantz Cateline , Le Pivert-Jolivet Tania , Loizeau Damien , Nakatoh Aiko , Okada Tatsuaki , Pilorget Cédric , Poulet François , Usui Tomohiro , Yada Toru , Yogata Kasumi , Moussi-Soffys Aurélie , Bibring Jean-Pierre
Published: July 2021

Introduction: On December 6, 2020, the Hayabusa2 mission successfully returned to Earth ~ 5.4 g of samples collected at the surface of the C-type asteroid Ruygu [1,2]. Its surface was first sampled on February 22, 2019, then on July 12, 2019, close to a 10-meter large artificial crater, so as to possibly access sub-surface material [3]. The collected samples are now kept at the Extraterrestrial Samples Curation Center of JAXA at ISAS in Sagamihara, Japan, for a first round of preliminary analyses, with the objective to characterize in a non-destructive manner both the bulk samples and a few hundreds of grains extracted from them [4]. In particular, the objective is 1) to support their further detailed characterization by the international initial analysis teams, which will start their activity in July 2021, and 2) to catalog the grains, accessible to the international community through AO selection, starting mid-2022.The preliminary characterization of these samples is being conducted with a visible microscope with four color filters, a FTIR spectrometer operating in the 1-5 µm range and MicrOmega, a hyperspectral NIR microscope developed at Institut d'Astrophysique Spatiale (Université Paris-Saclay/CNRS, Orsay, France), operating in the near-infrared range (0.99-3.65 µm) [5]. It is noteworthy that never before have the preliminary analyses of returned extraterrestrial samples included the characterization by a NIR hyperspectral microscope.Results: Preliminary outcomes of the analyses performed with MicrOmega will be presented at the conference. In particular, the question of the representativity of the samples collected by the Hayabusa2 spacecraft will be addressed thanks to the comparison of the spectra obtained by MicrOmega and the NIRS3 remote sensing IR spectrometer [6] which performed a spectral characterization (1.8-3.2 µm) of Ryugu's surface, including the sites of the samples' collection [7,8]. A preliminary analysis of the spatial compositional heterogeneity will be presented. Specific signatures, detected in grains typically present in
3D simulations of warm and hot Jupiter atmospheres: the role of 3D mixing in shaping CH4-to-CO conversion pathways
Authors: Zamyatina Maria , Hebrard Eric , Mayne Nathan , Drummond Benjamin
Published: July 2021

We present results from a set of cloud-free simulations of exoplanet atmospheres using a coupled three-dimensional (3D) hydrodynamics-radiation-chemistry model. We report in particular our investigation of the thermodynamic and chemical structure of the atmospheres of HAT-P-11b and WASP-17b and their comparison with the results for the atmospheres of HD 189733b and HD 209458b presented in Drummond et al. (2020). We found that the abundances of chemical species from simulations with interactive chemistry depart from their respective abundances computed at local chemical equilibrium, especially at higher latitudes. To understand this departure, we analysed the CH4-to-CO conversion pathways within the Venot et al. (2019) reduced chemical network used in our model using a chemical network analysis. We found that at steady state nine CH4-to-CO conversion pathways manifest in our 3D simulations with interactive chemistry, with different pathways dominating different parts of the atmosphere and their area of influence being determined by the vertical and horizontal advection and shifting between planets.
Experiments on rebounding slow impacts under asteroid conditions
Authors: Joeris Kolja , Schönau Laurent , Keulen Matthias , Born Philip , Kollmer Jonathan E.
Published: July 2021

The  surfaces  of  rubble-pile  asteroids  are  covered  in  regolith of a variety of sizes.  In some cases like for the asteroid Itokawa, the size distribution of regolith is not uniform across the surface [1]. Some areas are dominated by finer grains, while other areas are covered by larger rocks.  There are a number of competing explanations for this observed size segregation [2–4]. One approach is the so called ballistic-sorting-effect [2], where impacting particles sort themselves through different rebound behavior.In our work we want to set practical limits on the role ballistic sorting can play in shaping an asteroids surface. To this end we conduct a series of drop tower experiments examining the impact kinetics of slow (cm/s)  3 mm sized projectiles into a regolith surface under conditions realistic for asteroid surfaces, i.e. vacuum and low gravity. We track the impactor with high-speed cameras and determine its velocity in 3 dimensions before and after the impact. From these velocities, we can then compute a coefficient of restitution (COR).  We then repeat the experiment for surfaces composed of differently sized material.  We find that for a regolith bed made from particles of similar size as the impactor we get a lower COR (0,1) than for beds made up of significantly larger (0,5) or smaller particles (0,8). The more elastic collisions for larger sized targets follows from conservation of momentum. For the finer material we suggest that the higher COR is a function of interparticle adhesion.[1] A. Fujiwara, J. Kawaguchi, D.K. Yeomans, M. Abe, T. Mukai, T. Okada, J. Saito, H. Yano, M. Yoshikawa, D.J. Scheeres et al., Science 312, 1330 (2006)[2] T. Shinbrot, T. Sabuwala, T. Siu, M.V. Lazo, P. Chakraborty, Phys. Rev. Lett. 118, 111101 (2017)[3] S. Matsumura, D.C. Richardson, P. Michel, S.R. Schwartz, R.L. Ballouz, Mon. Not. the R. Astron. Soc. 443, 3368 (2014)[4] A.J. Dombard, O.S. Barnouin, L.M. Prockter, P.C. Thomas, Icarus 210, 713 (2010)