"CALM" was identified in the Akatsuki IR2 data acquired during Orbits 24 and 25 (August 2016) once data (in 2.26- and 1.735-um filters) were plotted in a special coordinate: the horizontal axis is the logarithm of radiance at 2.26 um while the vertical axis (basically the logarithm of radiance at 1.735 um) has been sheared such that the curve corresponding to varying amount of Mode 3 particles becomes almost level (M3L = Mode 3 Leveled). CALM appears as a concentration of data points in this correlation plot (Clouds Aligned Linearly in M3L coordinates) and is interpreted as relatively quiescent region in which aerosol sizes are determined by equilibrium. Because IR2 stopped working in December 2016, the available data set is quite limited. To identify more CALM-like regions and to characterize them, we have examined the data acquired by VIRTIS-M onboard Venus Express. Examples of CALM-like regions in VEx/VIRTIS-M data will be presented along with physical insights obtained through comparison with the Akatsuki/IR2 data.

In the Akatsuki radio occultation measurements, large temperature fluctuations were found in the upper atmosphere of Venus (over approximately 80 km). The typical vertical wave lengths of the observed temperature fluctuations are a few kilometers, and we expect that atmospheric gravity waves cause such temperature fluctuations in the altitude ranges. A general circulation model for the Venus based on the AFES (Atmospheric GCM for the Erath Simulation) model, which has an extremely high spatial resolution and can directly resolve the atmospheric gravity waves with horizontal wavelengths of several hundred kilometers (at the equator), qualitatively reproduced temperature fluctuations similar to the observations mentioned above. The temperature fluctuations distinctively appeared when we included thermal tides in the model, which suggests the relation of the observed temperature fluctuations to thermal tides.

The characteristics of gravity wave packets in the Venusian atmosphere were studied using high vertical resolution temperature profiles obtained by ESA’s Venus Express and JAXA’s Akatsuki radio occultation experiments with radio holographic methods. Localized disturbances were detected by applying wavelet transform to the temperature profiles. The packet lengths were found to be distributed over 0.6–10 km, in which typically 1.5–4 oscillations are included. The number of oscillations per wave packet was found to depend little on the wavelength; this tendency is essential for the power law dependence of the spectral density on the wavenumber in the saturation model. The peak spectral densities of the wave packets are roughly aligned with the saturation model spectrum, while the saturation ratio of each quasi-monochromatic wave is low. This suggests that the saturated spectrum is produced by the superposition of individually unsaturated quasi-monochromatic waves. Waves with short vertical wavelengths (<1.5 km) were found to be more prevalent at lower altitudes than at higher altitudes, implying an effect of radiative damping while upward propagation. The amplitude was found to be larger at higher latitudes; this might be attributed to the increase of the background static stability at high latitudes, which allows larger saturation amplitudes at higher latitudes.

Thermal structure (temperature and static stability) in the Venus atmosphere is reproduced by a general circulation model named AFES-Venus. A low-stability layer is maintained in low- and mid-latitudes at 50–60 km altitudes. High- and moderate-stability layers are located above 60 km and below 50 km, respectively. In the polar region, the low-stability layer is located at 46–63 km altitudes and the relatively low-stability layer is also found below it. In this study, the dynamical effects on the static stability below 65 km altitude were investigated. As a result, the heat transport due to the mean meridional circulation is important in low-latitudes. In mid- and high-latitudes, on the other hand, the baroclinic Rossby-type wave plays an important. We are going to talk about this point in more detail in the presentation.

For over twenty years, the episodic overturn model has been the reigning hypothesis to explain the relatively uniform surface ages on Venus. We revisit the model behind this hypothesis at an unprecedented scale, sampling close to twenty thousand complexly interdependent cases to capture a near-complete picture of the potential convection patterns of a putatively Venus-like planet. In particular, our ‘Big Data’ approach reveals a surprising, strong hysteresis effect at the mobile-episodic mode boundary: an observation which expands the range of conceivable early evolutionary pathways for Earth's twin world.

In-Situ Resource Utilisation (ISRU) of water assets from the lunar surface, especially from the volatile-rich polar regions, is a topic of significant current research. However, the term ISRU can encompass a much wider variety of potential resources and relevant extraction technologies. In a novel approach, rather than treating an extra-terrestrial feedstock using existing terrestrial methods of metal extraction, we have focussed on exploiting the ultra-high vacuum and high solar fluxes as key variables in designing the extractive process. Using computational thermodynamic modelling software, we have explored the thermodynamic effects of ultra-high vacuum conditions on high temperature systems leading to the discovery of a novel processing pathway that involves thermal decomposition at considerably lower temperatures than are usually associated with this pyrometallurgical process. In this presentation we outline a way for ISRU to extend beyond water to other valuable assets and propose a processing route for the extraction of Na, K and the beneficiation of FeO.

The unique ice giant planetary features of Uranus and Neptune are peculiar landscapes in the solar system. The two planets are surrounded by their own ring systems, and both ring systems are narrow and dark. We still have many curious parts about the ring systems of these two ice giant planets (such as the lack of micron dust in the rings of Uranus). That the Uranian rings are relatively free of dust has been explained in terms of the aerodynamic drag effect from collisional interaction with Uranus' exosphere. In this work, we explore the orbital motion of small charged dust particles and show that because of the highly offset and inclined dipole field of the planet, the trajectories could be very chaotic. As a consequence, the charged small dust particles would either hit the upper atmosphere of planets or escape to large distance (this fall pattern can span from the equatorial region to mid-high latitudes).  Besides depleting the dust content of the ring system, such a strong gravito-electrodynamical effect would also lead to the injection of CHON material into planet's atmosphere.

The “Ring Rain” effect with a large injection rate of nano-sized dust grains of ring origin falling into the Saturnian atmosphere, was detected by the Cassini Dust Analyzer (CDA), the Magnetospheric Imaging Instrument (MIMI), and the Ion Neutral Mass Spectrometer (INMS) during the Cassini Proximal mission. It was proposed that the collisional interaction between the entering dust grains and the exospheric gas particles will produce a thin disk of high-speed H-atoms and H₂-molecules in eccentric or escaping orbits (Mitchell et al., 2018). Also, the gas particles so accelerated might be correlated with a narrow hydrogen gas plume feature emitted from Saturn’s near-surface. (Shemansky et al., 2009). In this work, we re-investigate the orbital motion of dust particles generated by the D68 ringlet by considering different sizes of the dust grains, and further explore the dynamical behavior of the gas particles. The production rates of the high-speed H-atoms and H₂-molecules are estimated by using a series of Monte Carlo collision simulations. The collisions between nano-dust grains in Keplerian orbits and gas molecules of the corotating exosphere would lead to spiraling motion of the dust particles toward the planetary atmosphere, causing the dust particles to enter the atmosphere in less than 10 hours from ejection by the D68 ringlet.  The highest collision frequency of dust with a radius of 3 nm occurs at an altitude of 2000-2500 kilometers from the 1-bar level of the Saturnian atmosphere. In addition, the maximum post-collision velocity of the gas particles is close to 40 km/s at 7000 kilometers altitude and the high-speed hydrogen molecules generated on the equatorial plane have a high probability of escaping the Saturnian system. The density and orbital distributions of fast hydrogen atoms and molecules of such dust collision origin will be examined.

We present a first global survey of ion jets within current sheets around Mars. Among several observable effects of magnetic reconnection, Alfvénic plasma flows accelerated along and within current sheets, sometimes referred to as plasma jets, are often used as an indicator of the occurrence of magnetic reconnection. The global distributions and upstream driver dependences of magnetic reconnection at Mars remain largely unexplored, partly because comprehensive particle and field measurements were unavailable until the arrival of MAVEN. Here we developed an automated algorithm that efficiently and reliably identifies current sheet crossings and accelerated ion flows therein, and applied it to a large volume of MAVEN data obtained in the dayside and nightside magnetosphere of Mars. The statistical results are summarized as follows: (i) both of the sunward and anti-sunward ion jets embedded within current sheets are commonly found over a wide range of solar zenith angles, altitudes, and geographic locations in the Martian magnetosphere; (ii) on average, the sunward and anti-sunward jets are accompanied by the magnetic field configuration and topology consistent with those expected for reconnection; (iii) the jets appear to be observed irrespective of upstream driver conditions; and (iv) the identified current sheets are generally thin and embedded in low beta plasma. Utilizing the identified jet events, we also compute a preliminary estimate of ion escape rate by reconnection jets. The order-of-magnitude estimate of reconnection-driven ion escape rate suggests that direct acceleration of planetary ions by magnetic reconnection does not contribute significantly to the total ion escape from Mars. However, the ubiquitous presence of ion jets and current sheets seemingly capable of reconnection implies that magnetic reconnection could occur frequently in many locations in the Martian magnetosphere, thereby constantly reshaping pathways (i.e., open field lines) on which planetary ions escape to space.

Molten Regolith Electrolysis has been under development since 1963 as a process for extracting oxygen and metals from extraterrestrial soil. The process has a high technology-readiness-level, requires no additional separation processes to generate gaseous oxygen and castable metals, and is transferrable to terrestrial applications. A key limiting factor in implementation is our understanding of the electrode stability. Work in the previous decade has furthered the understanding of the chemical stability of polarized metals in molten oxides, with composition of the melt determined to be critical to the stability of the metal. During the process of electrolysis, the composition of the melt will change as oxygen and metal are removed, thus modeling of composition change is a critical first step in designing stable electrode materials. We present thermodynamic modeling to understand the species evolution during the electrolysis process. In addition to changes in chemical concentrations and activities, physical properties of the bath will also evolve. An intimate knowledge of the physical properties of the bath during the evolution of the composition is critical for the design of reactors. The design lifetime for viable off planet oxygen production is generally considered to be greater than five years. Viscosity, followed by electrical and ionic conductivity, and thermal conductivity of the bath have the greatest impact on reactor operation. Refractory and anode corrosion, as well as operational efficiency, are directly influenced by these properties. As a result, common physical property models will be presented which cover the temperature, pressure, and composition space available during electrolysis. Previous work on the oxide electrolysis of regolith has not considered how the thermochemical and physiochemical properties of the bath will change during the process. This work aims to fill that gap and will support high fidelity multi-physics modeling of the regolith electrolysis process.