DSMC simulations of volatile transport in a transient lunar atmosphere and ice deposition in cold traps after a comet impact

Over the years, a number of missions have detected signs of water and other volatiles in cold, permanently shadowed regions near the lunar poles, where temperatures are sufficiently low that volatile ices can remain stable over geological timescales. Several observations suggest that comet impacts may have played a role in delivering these cold-trapped volatiles. In this work, I use Direct Simulation Monte Carlo (DSMC) simulations to investigate the transport and sequestration of water in the aftermath of a lunar comet impact, focusing on developing a broad understanding of the physical processes that govern the fate of impact-delivered volatiles (particularly water), in order to better interpret remote sensing data. The sheer amount of vapor generated by a volatile-rich impact can transform the Moon’s tenuous, surface-bound exosphere into a collisional, transient atmosphere with characteristic gas dynamic features that influence the redistribution of impact-delivered volatiles. Notably, the simulations indicate that reconvergence of vapor antipodal to the point of impact may result in preferential redistribution of water in the vicinity of the antipode; in some circumstances, water may be distributed non-uniformly between different cold traps. It is also found that atmospheric self-shielding from photodestruction significantly increases the amount of water that reaches the shelter of cold traps. Volatile transport in an impact-generated atmosphere is also influenced by gas phase interactions with solar radiation and the lunar surface. The Moon has a distinctive surface thermal environment, characterized by large gradients in temperature over very small scales. In this work, I develop a stochastic rough surface temperature model that is then coupled to volatile transport simulations. It is found that surface roughness reduces the mobility of water at high latitudes, while also increasing the concentration of atmospheric/exospheric water molecules around the poles. I also implement a coupled DSMC-photon Monte Carlo method to model radiative heat transfer in the evolving, three-dimensional, rarefied atmosphere. The trapping of radiation within the optically thick gas slows the rate of cooling of the expanding vapor cloud, and also affects near-field atmospheric structure and winds. Ultimately, the fate of impact-delivered water is determined by the interplay between these factors.Aerospace Engineerin

Temperatures of the Lacus Mortis Region of the Moon

Over 11&nbsp;years of data acquired by the Diviner Lunar Radiometer Experiment instrument aboard Lunar Reconnaissance Orbiter have been compiled into a comprehensive data set of surface temperatures in the Lacus Mortis region which includes the landing ellipse of the Astrobotic Mission One lander mission. These data provide diurnal brightness temperatures at 128 pixels per degree (ppd) spatial resolution and 0.1&nbsp;hr of local time resolution. From this data set, we highlight several features that display variations in radiative and thermophysical properties in the Lacus Mortis region and characterize the temperatures of the Astrobotic Mission One landing ellipse. We identify distinctly contrasting properties of materials in the walls of B&uuml;rg crater, hummocks of materials on the southeast margin of the mare basalts, and materials exposed or excavated by impacts. Additionally, we describe an exceptionally rocky fault scarp that predates the formation of B&uuml;rg crater suggesting the observed boulders are replenished on a timescale &lt;1&nbsp;Ga. Within the Astrobotic landing ellipse, temperatures are observed to range from &sim;88 to &sim;359&nbsp;K with sunrise and sunset local times constrained to 5.8&ndash;6.3&nbsp;hr and 17.8 and 18.1&nbsp;hr respectively. &nbsp;</p

Science Opportunities offered by Mercury's Ice-Bearing Polar Deposits

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Lunar Volatiles and Solar System Science

Understanding the origin and evolution of the lunar volatile system is not only compelling lunar science, but also fundamental Solar System science. This white paper (submitted to the US National Academies' Decadal Survey in Planetary Science and Astrobiology 2023-2032) summarizes recent advances in our understanding of lunar volatiles, identifies outstanding questions for the next decade, and discusses key steps required to address these questions

Computational modelling of the aerodyanmics and flight mechanics of a boomerang

The returning boomerang is a singularly interesting device: when thrown spinning in a near-vertical plane, rather than travelling along a straight line, the boomerang turns continuously to the left and ultimately returns to its thrower. The return of the boomerang is caused by two types of gyroscopic precession, the result of an interaction between the lift generated by the boomerang’s arms, and its initial angular velocity. This project aims to apply an understanding of the physics of boomerang flight, and the principles of Computational Fluid Dynamics in order to model the boomerang as a rigid body with six-degrees of freedom, within the framework of the STAR-CCM+ software. In order to initialise the six degree-of-freedom simulation, a steady-state simulation of the boomerang, at the instant just before it leaves the thrower’s hand, is carried out. The steady-state pressure distribution reveals an imbalance in the lift produced by the two arms of the boomerang, which reinforces the gyroscopic precession of its angular velocity vector. Using the results of the steady-state simulation, a six degree-of-freedom simulation is initialised. This simulation solves the governing equations to simulate the motion of the boomerang in response to pressure and shear forces exerted by the air surrounding it. From this, the trajectory of the boomerang is obtained and is found to be typically curved and returning. The nature of the trajectory is analysed in greater depth. The changes in the boomerang’s orientation are also studied, and its aerodynamic loading reveals how the rapid translation and rotation of its rotor blade-like arms results in the generation of lift. Lastly, the development of vortical structures in the wake of the boomerang is studied. It is observed that the motion of air around the boomerang is influenced governed largely by the interaction of tip vortices generated and shed by its arms, with flows induced by pressure differences on and across its surfaces. In additional to the results above, this report discusses the constraints encountered in setting up a computational model, and offers recommendations for further work.Bachelor of Engineering (Aerospace Engineering

Exosphere-Mediated Migration of Volatile Species On Airless Bodies Across the Solar System

Surface-bound exospheres facilitate volatile migration across the surfaces of nearly airless bodies. However, such transport requires that the body can both form and retain an exosphere. To form a sublimation exosphere requires the surface of a body to be sufficiently warm for surface volatiles to sublime; to retain an exosphere, the ballistic escape and photodestruction rates and other loss mechanisms must be sufficiently low. Here we construct a simple free molecular model of exospheres formed by volatile desorption/sublimation. We consider the conditions for forming and retaining exospheres for common volatile species across the Solar System, and explore how three processes (desorption/sublimation, ballistic loss, and photodestruction) shape exospheric dynamics on airless bodies. Our model finds that the CO2 exosphere of Callisto is too dense to be sustained by impact-delivered volatiles, but could be maintained by only ~7 hectares of exposed CO2 ice. We predict the peak surface locations of Callisto's CO2 exosphere along with other Galilean moons, which could be tested by JUICE observations. Our model finds that to maintain Iapetus' two-tone appearance, its dark Cassini Regio likely has unresolved exposures of water ice, perhaps in sub-resolution impact craters, that amount to up to ~0.06% of its surface. In the Uranian system, we find that the CO2 deposits on Ariel, Umbriel, Titania, and Oberon are unlikely to have been delivered via impacts, but are consistent with both a magnetospheric origin or sourced endogenously. We suggest that exosphere-mediated volatile transport could produce these moons' leading/trailing CO2 asymmetries, and may be a seasonal equinox feature that could be largely erased by volatile migration during the Uranian solstices. We calculate that ~2.4-6.4 mm thick layer of CO2 could migrate about the surface of Uranus' large moons during a seasonal cycle

The Value of the Moon for Heliophysics

International audienceThe Moon represents an ideal heliophysics laboratory for the investigation of kinetic plasma physics, in situ measurements of the interplanetary and terrestrial environment, and remote measurements of geospace and beyond. Frequent future planned launches to the lunar vicinity, and international interest, make the Moon an appealing and accessible target for valuable heliophysics investigations

Abstracts of National Conference on Biological, Biochemical, Biomedical, Bioenergy, and Environmental Biotechnology

This book contains the abstracts of the papers presented at the National Conference on Biological, Biochemical, Biomedical, Bioenergy, and Environmental Biotechnology (NCB4EBT-2021) Organized by the Department of Biotechnology, National Institute of Technology Warangal, India held on 29–30 January 2021. This conference is the first of its kind organized by NIT-W which covered an array of interesting topics in biotechnology. This makes it a bit special as it brings together researchers from different disciplines of biotechnology, which in turn will also open new research and cooperation fields for them. Conference Title: National Conference on Biological, Biochemical, Biomedical, Bioenergy, and Environmental BiotechnologyConference Acronym: NCB4EBT-2021Conference Date: 29–30 January 2021Conference Location: Online (Virtual Mode)Conference Organizer: Department of Biotechnology, National Institute of Technology Warangal, Indi