The heat flow and physical properties package (HP$^3$) of the InSight Mars mission is an instrument package designed to determine the martian planetary heat flow. To this end, the package was designed to emplace sensors into the martian subsurface and measure the thermal conductivity as well as the geothermal gradient in the 0-5 m depth range. After emplacing the probe to a tip depth of 0.37 m, a first reliable measurement of the average soil thermal conductivity in the 0.03 to 0.37 m depth range was performed. Using the HP$^3$ mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 $\pm$ 0.002 W m$^{-1}$ K$^{-1}$, consistent with the results of orbital and in-situ thermal inertia measurements. This low thermal conductivity implies that 85 to 95\% of all particles are smaller than 104-173 $\mu$m and suggests that any cement contributing to soil cohesion cannot significantly increase grain-to-grain contact areas by forming cementing necks, but could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are 1211$_{-113}^{+149}$ kg m$^{-3}$, indicating soil porosities of 61 \%.

Energetic charged particles ~>40 keV can affect the plasma temperature and pressure and as a consequence the whole dynamics of the magnetosphere. How do particles get to such energies is a fundamental science question. Energetic particles are also potentially hazardous for the space observations. It is, therefore, necessary to study the origin of energetic plasma, its acceleration, distribution and consequences on the magnetospheric dynamics. In this work we review the related results based on observations from the Cluster/RAPID energetic charged particle detector. These results represent new insights in plasma acceleration, unexpected features in its distributions, effects on substorm and geomagnetic storm dynamics and remediated observations in the radiation belts during approximately 1.5 solar cycles.

Venus is the most Earth-like of the terrestrial planets, though very little is known about its surface composition. Thanks to recent advances in laboratory spectroscopy and spectral analysis techniques, this is about to change. Although the atmosphere prohibits observations of the surface with traditional imaging techniques over much of the EM spectral range, five transparent windows between ~0.86 µm and ~1.18 µm occur in the atmosphere’s CO2 spectrum. New high temperature laboratory spectra from the Planetary Spectroscopy Laboratory at DLR show that spectra in these windows are highly diagnostic for surface mineralogy [1]. The Venus Emissivity Mapper (VEM) [2] builds on these recent advances VEM is the first flight instrument specially designed to focus solely on mapping Venus’ surface using the windows around 1 µm. Operating in situ from Venus orbit, VEM will provide a global map of composition as well as redox state of the surface, enabling a comprehensive picture of surface-atmosphere interaction on Venus. VEM will return a complex data set containing surface, atmospheric, cloud, and scattering information. Total planned data volume for a typical mission scenario exceeds 1TB. Classical analysis techniques have been successfully used for VIRTIS on Venus Express [3-5] and could be employed with the VEM data. However, application of machine learning approaches to this rich dataset is vastly more efficient, as has already been confirmed with laboratory data. Binary classifiers [6] demonstrate that at current best estimate errors, basalt spectra are confidently discriminated from basaltic andesites, andesites, and rhyolite/granite. Applying the approach of self-organizing maps to the increasingly large set of laboratory measurements allows searching for additional mineralogical indicators, especially including their temperature dependence. [1] Dyar M. D. et al. 2017 LPS XLVIII, #1512. [2] Helbert, J. et al. 2016. San Diego, CA, SPIE. [3] Smrekar, S.E., et al. Science, 2010 328(5978), 605-8. [4] Helbert, J., et al., GRL, 2008 35(11). [5] Mueller, N., et al., JGR, 2008 113. [6] Dyar M. D. et al. 2017 LPS XLVIII, #3014.

Nightside magnetospheric processes (dynamics) directly reflect to auroral morphology and type. By investing type of auroras and the auroral morphological changes, we can expect to understand what physical processes would take place in the magnetotail. Under northward Interplanetary Magnetic Field (IMF) conditions, transpolar arcs (TPAs) and aurora spiral can be observed. A source of TPA is considered as field-aligned currents induced by the plasma flow shear (including the plasma flow vortices) between the fast plasma flows generated by magnetotail magnetic reconnection and slower background magnetospheric plasma flows. On the other hand, it is well-known that aurora spiral is also likely to be formed by the field-aligned current induced by the flow shear in the magnetotail, such as the Kelvin-Helmholtz instabilities. Based on the contemporaneous observations of TPA and aurora spiral, we try to investigate (diagnose) how the plasma and its energy are transported in the nightside magnetosphere toward ionosphere under northward IMF conditions. On January 10th, 1997, transpolar arc (TPA) and aurora spiral contemporaneously occurred for about 5.5 hours between 17:58 UT and 22:23 UT even when Interplanetary Magnetic Field (IMF) orientation changed from weakly southward to northward at ~21:00 UT. Because no in-situ magnetotail observations were unfortunately found in this day, we performed global MHD simulations based on the Open Geospace General Circulation Model (Open GGCM) distributed in the Community Coordinated Modeling Center (CCMC), and discussed the physical relation between two different auroral appearances and nightside magnetospheric processes. In this simulation, after the IMF-Bz orientation turned from weakly southward to northward, clear flow shear between fast earthward plasma flows triggered by magnetotail reconnection and slower tailward background magnetospheric flows was seen around Xgsm ~ -40 Re in the dawn sector, being consistent with the TPA and aurora spiral brightening. These flow shears may be a “source” of field-aligned currents to form the TPA. Furthermore, they bifurcated toward dawn and dusk, and showed stronger vortices in the dusk region than those in the dawnward sector. These vortex(-like) structures, bifurcated duskward, and associated field-aligned currents would be linked to the formation of the aurora spiral. In this presentation, we will discuss further the relation between the variations of these flow shear (vortex) structures, TPA and aurora spiral formations under northward IMF conditions, followed by weak southward IMF intervals.

According to the different orientations of the interplanetary magnetic field (IMF), the planetary shock can be either quasi-parallel or quasi-perpendicular. Under quasi-parallel conditions a significant number of solar wind suprathermal particles are reflected from the shock and drift along IMF, forming an extended and highly turbulent region called the foreshock where various nonlinear plasma phenomena are observed. In this research, we perform a case study of the structures in the foreshock region at Mars observed by Mars Atmosphere and Volatile Evolution (MAVEN). We use data from plasma analyzer STATIC and magnetometer MAG to analyze ion beams angular spectrum and magnetic field dynamics. We show that the observed structures are consistent with Short Large-Amplitude Magnetic Structures (SLAMS), commonly detected in foreshock regions of magnetized and unmagnetized bodies throughout the Solar system. Finally, we calculate the magnetic Mach number to analyze the characteristics of the observed foreshock structures. The analysis shows, that SLAMS are formed by the resonance between plasma waves propagating along the IMF and the backstreaming scattered solar wind H+ and exospheric O+ and O2+ ions, with the dominant impact of O2+ ions.

We present an initial assessment of using tomography on single-spacecraft images to reconstruct 3D X-ray emissions from the Earth’s magnetosheath. 3D structures in the Earth’s magnetosphere have been studied using superposed epoch techniques with single-point single-spacecraft observations. They have yielded great insights, but some studies are observation starved, particularly for infrequent solar wind conditions. Global imaging data have provided more insight about these structures, but are 2D projections of 3D structures. We explore the use of tomographic reconstruction techniques to understand what can be extracted from global images from a single spacecraft. The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission, due to launch in 2024 on a 3-year mission, will carry a soft X-ray imager which will capture emissions from portions of the magnetosheath and upstream solar wind. We already demonstrated that the 3D shape of the magnetopause and the bow shock can be extracted from such images with suitable assumptions. The next step is to examine whether full 3D reconstructions of the emissions are possible. We explore the limited range of viewing angles, which affect the accuracy of the reconstructions and introduce artifacts in some cases, and the low count-rates in the images which introduce noise in the reconstructions which must be filtered out. Despite these limitations we show that it is possible to reconstruct some aspects of the magnetosheath global morphology using single-spacecraft soft X-ray imaging. Plans for similar missions which overlap with SMILE, open the possibility of multi-spacecraft tomography, to be addressed in a separate paper.

Turbulent plasmas such as the solar wind and magnetosheath exhibit an energy cascade which is present across a broad range of scales, from the stirring scale at which energy is injected, down to the smallest scales where energy is dissipated through processes such as reconnection and wave-particle interactions. Recent observations of Earth's bow shock reveal a disordered or turbulent transition region which exhibits features of turbulent dissipation, such as reconnecting current sheets. We have used observations from Magnetospheric Multiscale (MMS) over four separate bow shock crossings of varying θBn to characterise turbulence in the shock transition region and how it evolves towards the magnetosheath. We observe the magnetic spectrum evolving by fitting power laws over many short intervals and find that the power-law index in the shock transition region is separable from that of the upstream and downstream plasma, for both quasi-perpendicular and quasi-parallel shocks. Across the shock, we see a change in the breakpoint location between inertial and ion power-law slopes. We also observe the evolution of scale-independent kurtosis of magnetic fluctuations across the shock, finding a reduction of high kurtosis intervals downstream of the shock, which is more apparent in the quasi-perpendicular case. Finally, we adapt a method for calculating correlation length to include a high-pass filter, allowing estimates for changes in correlation length across Earth's bow shock. In a quasi-perpendicular shock, we find the correlation length to be significantly smaller in the magnetosheath than in the solar wind, however the opposite can occur for quasi-parallel shocks.

Our solar system is filled with meteoric particles, or cosmic dust, which is either interplanetary or interstellar in origin. Interstellar dust (ISD) enters the heliosphere due to the relative motion of the sun and the interstellar flow. Interplanetary dust (IPD) comes primarily from asteroid collisions or comet sublimation, and comprises the bulk of material entering Earth’s atmosphere. This study examines variations in ISD and the IPD flux at Earth using observations from three different satellite techniques. First are size-resolved in situ meteoroid detections by the Ulysses spacecraft, and second are in situ indirect dust observations by Wind. Third are measurements of meteoric smoke in the mesosphere by the Solar Occultation For Ice Experiment (SOFIE). Wind observations are sorted into the interstellar and interplanetary components. Wind ISD show the anticipated correlation to the 22-yr. solar magnetic cycle, and are consistent with model predictions of ISD. Because Wind does not discriminate particle size, the IPD measurements were interpreted using meteoric mass distributions from Ulysses observations and from different models. Wind observations during 2007-2020 indicate a total meteoric influx at Earth of 22 metric tons per day (t d-1), in reasonable agreement with long-term averages from SOFIE (25 t d-1) and Ulysses (32 t d-1). The SOFIE and Wind influx time series both show an unexpected correlation to the 22-yr. solar cycle. This relationship could be an artifact, or may indicate that IPD responds to changes in the solar magnetic field.

An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field-aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<~1 min) response of the ionosphere-thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ~6 s resolution SuperDARN ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ~1 min before moving upward. By contrast, the post-midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversed E X B vertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC.

Spacecraft charge mitigation is critical for a host of space plasma measurement techniques. However, charge mitigation in tenuous space plasmas can be a difficult problem. It is especially difficult and essential during active experiments that feature ion or electron beams, as collection from the ambient plasma is often insufficient to balance the beam emission current. For electron emission experiments, the use of a plasma contactor that emits an ionized gas is the only practical option. A series of parametric chamber experiments were completed to address how spacecraft charge mitigation using a plasma contactor may scale in tenuous space plasmas. Experiments focus on how spacecraft potential scales with beam emission current, contactor current (the rate at which the contactor generates quasi-neutral plasma), and contactor expellant mass (ion mass). These experimental results are compared to scaling laws derived via Curvilinear Particle-In-Cell (CPIC) simulations for further validation and physical insights. Implications for improving space plasma measurements and enabling future active experiments such as the Connections Explorer (CONNEX) mission are discussed.

Whistler waves are often observed in magnetopause reconnection associated with electron beams. We analyze seven MMS crossings surrounding the electron diffusion region (EDR) to study the role of electron beams in whistler excitation. Waves have two major types: (1) Narrow-band waves with high ellipticities and (2) broad-band waves that are more electrostatic with significant variations in ellipticities and wave normal angles. While both types of waves are associated with electron beams, the key difference is the anisotropy of the background population, with perpendicular and parallel anisotropies, respectively. The linear instability analysis suggests that the first type of wave is mainly due to the background anisotropy, with the beam contributing additional cyclotron resonance to enhance the wave growth. The second type of distribution excites broadband waves via Landau resonance, and as seen in one event, the beam anisotropy induces an additional cyclotron mode. The results are supported by particle-in-cell simulations. We infer that the first type occurs downstream of the central EDR, where background electrons experience Betatron acceleration to form the perpendicular anisotropy; the second type occurs in the central EDR of guide field reconnection. A parametric study is conducted with linear instability analysis. A beam anisotropy alone of above ~3 likely excites the cyclotron mode waves. Large beam drifts cause Doppler shifts and may lead to left-hand polarizations in the ion frame. Future studies are needed to determine whether the observation covers a broader parameter regime and to understand the competition between whistler and other instabilities.

Many processes throughout the heliosphere such as flares, CMEs, storms and substorms have abrupt onsets. The waiting time between these onsets provides key insights as to the underlying dynamical processes. We explore the tail of these waiting time distributions in the context of random processes driven by the solar magnetic activity cycle, which we approximate by a sinusoidal driver. Analytically, we find that the distribution of large waiting times of such a process approaches a power law slope of -2.5 at large enough waiting time, and we find that this power law is primarily controlled by the conditions when the driving is minimum. We find that the asymptotic behavior of the waiting time distributions of solar flares, coronal mass ejections, geomagnetic storms, and substorms exhibit power laws are in reasonable agreement with a sinusoidally driven nonstationary Poisson process.

Knowledge of the ambient solar wind is important for accurate space-weather forecasting. A simple-but-effective method of forecasting near-Earth solar-wind conditions is “corotation”, wherein solar-wind structure is assumed to be fixed in the reference frame rotating with the Sun. Under this approximation, observations at a source spacecraft can be rotated to a target location, such as Earth. Forecast accuracy depends upon the rate of solar-wind evolution, longitudinal and latitudinal separation between the source and target, and latitudinal structure in the solar wind itself. The time-evolution rate and latitudinal structure of the solar wind are both strongly influenced by the solar cycle, though in opposing ways. A latitudinal offset is typically present, introducing an error to corotation forecasts. In this study, we use observations from the STEREO and near-Earth spacecraft to quantify the latitudinal error. Aliasing between the solar cycle and STEREO orbits means that individual contributions to the forecast error are difficult to isolate. However, by considering an 18-month interval near the end of solar minimum, we find that the latitudinal-offset contribution to corotation-forecast error cannot be directly detected for offsets <6º, but is increasingly important as offsets increase. This result can be used to improve solar-wind data assimilation, allowing representivity errors in solar-wind observations to be correctly specified. Furthermore, as the maximum latitudinal offset between L5 and Earth is ≈5º, corotation forecasts from a future L5 spacecraft should not be greatly affected by latitudinal offset.

The Space Physics Data Facility (SPDF https://spdf.gsfc.nasa.gov), as the non-solar NASA Heliophysics active final archive, works with current operating missions and the heliophysics community to ingest, preserve and serve a wide range of past and current public science-quality data from the mesosphere into the furthest reach of deep-space exploration. SPDF facilitates scientific analysis of multi-instrument and multi-mission datasets to enhance the science return of the many missions. SPDF develops and maintains the Common Data Format (CDF) and the associated ISTP/SPDF metadata guidelines. SPDF services include CDAWeb, which supports both survey and burst mode data with graphics, listings and data superset/subset functions. All public data held by SPDF are also available for direct file download by HTTPS or FTPS links from the SPDF home page (https://spdf.gsfc.nasa.gov). SPDF is currently receiving and serving from missions including Parker Solar Probe, MMS, Van Allen Probes, THEMIS/ARTEMIS, GOLD, ACE, Cluster, IBEX, Voyager, Geotail, Wind and many others, and >120 Ground-Based investigations. SPDF recently added support for ARASE/ERG and MAVEN as supplementary access at the requests of those missions, and is expecting Solar Orbiter and ICON data. SPDF also operates the multi-mission orbit displays and query services of SSCWeb and the Java-based 4D Orbit Viewer, as well as the Heliophysics Data Portal (HDP) discipline-wide data inventory and access service, and OMNIWeb and COHOWeb for near-Earth and deep-space solar wind plasma, magnetic field, and energetic particle database, respectively.

Space traffic management is difficult. Monitoring and predicting the accurate, real-time position of satellites for collision avoidance in low earth orbit is an engineering challenge. The dominant source of error in satellite prediction tracking models is in the determination of space weather driven atmospheric drag. The High Accuracy Satellite Drag Model (HASDM) (Storz et al., 2005) was developed by the U.S. Air Force Space Command (AFSPC) between 2000–2005 to help solve this problem. It is a data assimilative modeling system using the JB2008 thermospheric density model (Bowman et al., 2008) plus continuously derived densities from several dozens of calibration satellites to achieve <5% density uncertainty at most epochs. The HASDM data is being made available to the community of scientists and operators for the first time. Under authority from the AFSPC, Space Environment Technologies (SET) has extracted two solar cycles of operational High Accuracy Satellite Drag Model (HASDM) data for scientific use and this is called the SET HASDM database. Navigating and extracting information from this database quickly and efficiently to manage satellite space traffic is currently complex and tedious. We present the development of a data-driven model for the HASDM mass density using Machine Learning and an attempt to quantify the associated uncertainties.

Combining geologic mapping and stratigraphic reconstruction of lava flows at Sapas, Maat and Ozza Montes, three potentially young volcanic structures of Atla Regio on Venus, with analysis of the spectral signature (radar emissivity anomalies) characterizing each mapped flow, Brossier et al. (2021) conclude that some of the lava flows at Maat Mons may be geologically recent (~25 Ma). The lava flows of Sapas and Ozza Montes are more consistent with weathered lava flows forming chlorapatite and some perovskite oxides. We discuss the reasons why, besides the importance of the results they obtained, the methodology they used can be very valuable for future investigations with higher resolution datasets. The importance of combining geologic interpretation with spectral analysis in the reconstruction of the volcanic history of Venus Considering its size, gravity and the presence of an atmosphere, Venus is typically considered as the twin sister of the Earth, but despite the apparent similarities with our planet, Venus is notably different because it is characterized by its extreme surface environment. With 90 bars and 475 °C, its surface is a very inhospitable place for life as we know it. Venus does not show evidence for a present plate tectonics-like activity, having a major part of its surface volcanic deposits younger than 300 Ma. It has been hypothesized that Venus underwent a catastrophic event of global resurfacing about 300 Ma ago, which may have almost entirely rejuvenated its surface (Schaber, 1992; Nimmo and McKenzie, 1998; Romeo and Turcotte, 2010; Strom et al., 1994; Turcotte et al., 1999). Some other studies instead favor a more equilibrium resurfacing model of the surface (Phillips et al, 1992; Phillips and Hansen, 1994; Bjonnes et al., 2012; O’Rourke and Korenaga, 2015). It is also possible that the past volcanic history of Venus somehow reflected an intermediate situation between these two end-member scenarios. Related to this topic, there has been a subject of debate whether or not the volcanism on Venus is currently evolving toward an equilibrium stage, with occurrences of smaller and more frequent localized eruptions. In this regard, it is vital to identify areas with current or recent volcanism, to measure the actual rate and volume of the most recent volcanic eruptions. The geologic interpretation and analysis of spectral signatures (both in radar and infrared wavelengths) can help us constraining the age of surface volcanic deposits on Venus. In geology, the so called “cross-cutting interrelationships” can constrain the relative age of two lava flows as it has been applied to young, possibly very recent lava flows and tectonic features on

Generation and propagation of lower hybrid drift wave (LHDW) within and near the electron diffusion region (EDR) during guide field reconnection at the magnetopause is studied with data from the Magnetospheric Multiscale mission and a theoretical model. Inside the EDR where the electron beta is high (β ~ 5), the long-wavelength electromagnetic LHDW propagating obliquely to the local magnetic field is observed. In contrast, the short-wavelength electrostatic LHDW propagating nearly perpendicular to the local magnetic field is observed slightly away from the EDR, where β is small (~0.6). These observed LHDW features are explained by a local theoretical model only after including effects from the electron temperature anisotropy, finite electron heat flux and parallel current. The short-wavelength LHDW is capable of generating significant drag force between electrons and ions.

The commercial sector of space science is thriving. Exciting examples come to mind more easily today than ever before, including commercial spaceflight and launches, ride shares for public-sector missions, and the deployment of countless satellites that support communications and human infrastructure. What may be surprising to some is the breadth and depth of the private sector contribution that goes beyond the largest, most high-profile examples. Companies, large and small, are doing fundamental science, and becoming high-quality data providers.

Analyses of meteorites in thin or thick section begins with a detailed mineralogic/petrologic study of the sample. Backscattered electron and x-ray imaging in a secondary electron microscope is critical for the characterization and study of the meteorite sections at sub-$\mu$m to cm size scales. Here, I describe techniques to acquire backscattered electron and x-ray images of an entire one-inch thin or thick section at high resolution, assemble large mosaic mosaic maps of the data, and display the maps conveniently online in a web browser. The code to acquire, stitch, and display the maps is made available as an open-source project.

Accurate forecasting of the arrival time and arrival speed of coronal mass ejections (CMEs) is a unsolved problem in space weather research. In this study, a comparison of the predicted arrival times and speeds for each CME based, independently, on the inputs from the two STEREO vantage points is carried out. We perform hindcasts using ELlipse Evolution model based on Heliospheric Imager observations (ELEvoHI) ensemble modelling. An estimate of the ambient solar wind conditions is obtained by the Wang-Sheeley-Arge/Heliospheric Upwind eXtrapolation (WSA/HUX) model combination that serves as input to ELEvoHI. We carefully select 12 CMEs between February 2010 and July 2012 that show clear signatures in both STEREO-A and STEREO-B HI time-elongation maps, that propagate close to the ecliptic plane, and that have corresponding in situ signatures at Earth. We find a mean arrival time difference of 6.5 hrs between predictions from the two different viewpoints, which can reach up to 9.5 hrs for individual CMEs, while the mean arrival speed difference is 63 km s$^{-1}$. An ambient solar wind with a large speed variance leads to larger differences in the STEREO-A and STEREO-B CME arrival time predictions ($cc = 0.92$). Additionally, we compare the predicted arrivals, from both spacecraft, to the actual in situ arrivals at Earth and find a mean absolute error of 7.5 $\pm$ 9.5 hrs for the arrival time and 87 $\pm$ 111 km s$^{-1}$ for the arrival speed. There is no tendency for one spacecraft to provide more accurate arrival predictions than the other.

While not specifically designed as a planetary mission, NASA’s Parker Solar Probe (PSP) mission uses a series of Venus gravity assists (VGAs) in order to reduce its perihelion distance. These orbital maneuvers provide the opportunity for direct measurements of the Venus plasma environment at high cadence. We present first observations of kinetic scale turbulence in the Venus magnetosheath from the first two VGAs. In VGA1, PSP observed a quasi-parallel shock, $\beta\sim1$ magnetosheath plasma, and a kinetic range scaling of $k^{-2.9}$. VGA2 was characterised by a quasi-perpendicular shock with $\beta\sim 10$, and a steep $k^{-3.4}$ spectral scaling. Temperature anisotropy measurements from VGA2 suggest an active mirror mode instability. Significant coherent waves are present in both encounters at sub-ion and electron scales. Using conditioning techniques to exclude these electromagnetic wave events suggests the presence of developed sub-ion kinetic turbulence in both magnetosheath encounters.

The formation of layers at mid-latitudes has been related to neutral winds activity at altitudes below 130km in the Mesosphere and Lower Thermosphere (MLT). Recent SAMI3 simulations by Krall et al. (2020) of ionospheric metallic layers at Arecibo suggest that forces induced by the meridional winds cause low altitude layers near 100 km. However, the classic mechanism, originally proposed by Whitehead (1961), correctly states that zonal wind shear has a bigger effect than meridional wind shear in the lower E region. Haldoupis and Shalimov (2021), referring to observations of ionosonde-based sporadic E statistics and radio occultation sporadic E measurements using low Earth orbiting satellites, support the idea that zonal winds dominate layer formation at these altitudes, apparently disputing the findings of Krall et al. (2020). Perhaps the latest technique to continuously measure mid-latitude MLT daytime neutral winds was developed by Hysell et al. (2014). That technique used a unique configuration of the Arecibo radar dual-beam. Unfortunately, since Arecibo lost the capability of the dual-beam in 2017 (when one antenna was destroyed by Hurricane Maria), there are only few valuable data sets that can help elucidate the origin of the lower altitude layers at Arecibo. We present Arecibo neutral wind data correlated with lower altitude layers. While not disputing current theory, we find that, near 100 km, meridional neutral wind shear can be much stronger than zonal wind shear when a layer is present, with the meridional shear correctly positioned to support the layer. We also present a complete analysis of the vertical ion drift, including declination, where the meridional winds become more important and with a reversed mechanism for altitudes below 115km for Arecibo conditions. References: Haldoupis et al. (2021), https://doi.org/10.1016/j.jastp.2021.105537 Hysell et al. (2014), http://doi.org/10.1002/2013JA019621 Krall et al. (2020), https://doi.org/10.1029/2019JA027297

Many of the unusual properties of the dwarf planet Pluto's orbit are widely accepted as evidence for the orbital migration of the giant planets in early solar system history. However, some properties remain an enigma. Pluto's long term orbital stability is supported by two special properties of its orbit that limit the location of its perihelion in azimuth and in latitude. We revisit Pluto's orbital dynamics with a view to elucidating the individual and collective gravitational effects of the giant planets on its perihelion location. In this presentation we demonstrate with numerical experiments that, while the resonant perturbations from Neptune account for the azimuthal constraint on Pluto's perihelion location, the long term and steady persistence of the latitudinal constraint is possible only in a narrow range of additional secular forcing which arises fortuitously from the particular orbital architecture of the other giant planets. Our numerical investigations also find that Jupiter has a largely stabilizing influence whereas Uranus has a largely destabilizing influence on Pluto's orbit.

Mars’ ultraviolet airglow has been used to study its upper atmosphere for over four decades. Identifying variations in emission features has provided information on composition, density and temperature. The Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission observes Mars’ airglow at Far and Extreme UV wavelengths. Variations in disk emission features are studied, with a focus on O I 1304 Å, CO Fourth Positive Group and C I 1561 Å. All show variations with local time and emission angle as expected. Dawn-dusk asymmetry observed is attributed to local time differences in advection. Variations in the brightness of several dayglow features, including 1304 Å, with irregular shapes are noted in around 25% of the disk images. These display some local time and hemispheric asymmetry in their occurrence rates. Examination of their spatial structure, occurrence, and spectra suggests these are associated with variations in composition and photoelectron flux.