Optical PhotoThermal InfraRed (O-PTIR) is a relatively new spectroscopy method for studying materials. It produces transmission-like spectra using a remote reflectance technique that is rapid, requires little sample preparation, and is well-suited for the technique to be adapted for a space flight instrument. The method involves a tunable pulsed IR laser creating a photothermal effect on the surface of a material and measuring the distortion of a probing visible laser in the same region of the sample, which can be obtained at sub-micron spatial resolutions. A measurement campaign was performed utilizing Photothermal Spectroscopy Corporation's O-PTIR instrument, mIRage®. In this campaign, individual minerals were analyzed using the O-PTIR technique, and their spectra were compared to existing transmission and reflectance spectra. Additionally, Space Resource Technologies (SRT) soil simulant mixtures were also analyzed to attempt to determine mineral contributions to the mixtures' spectra. Samples were prepared using cylindrical sample holders adhered to glass slides which could easily and cleanly be mounted into the instrument. Hyperspectral maps of various sizes (dependent on grain size) were made, and their spectra were averaged to produce a single spectrum for each mineral and mixture. Constituent material spectra were compared to available spectra based on spectral features and corresponding peaks. Similarly, various SRT simulants representative of lunar (LHS-2, LMS-2, and LSP-2) and martian (JHZ-1 and MGS-1) surfaces were analyzed as well as their constituent materials in order to determine the contribution each mineral makes to the simulant mixture. It was found that data produced with the mIRage® instrument closely resembled transmission spectra in most cases and shared spectral shapes with reflectance spectra at mid-IR wavenumbers (980 - 1800 cm−1 ). Further, the instrument's performance was found to outperform commonly used techniques regarding speed, in some cases spatial resolution, and a reduced need for sample preparation. This work will support future prototyping of an instrument for in situ material analysis.

<p>While hypervelocity impacts are ubiquitous throughout the solar system and have received decades  of  research,  the dynamic  fragmentation that  occurs  during an impact has received relatively little attention. This is made more troublesome by the fact that, by volume, more material in the target is altered by the tensile stresses of the rarefaction wave that relieves the pressure of the shock wave, compared to the amount excavated by the impact itself. This tensionally affected material  can  include  Grady-Kippfragments,  fragments  of  material  that  were  broken  apart according to a dynamic fragmentation model developed by Grady and Kipp in 1980. By using their model and inserting it into the Eulerian hydrocode iSALE, we have been able to examine the role tensile stressesand dynamic fragmentation play in hypervelocity impacts. We started by finding the limits on Grady-Kipp fragmentation on an already well studied surface, the Moon. We found that fragment sizes are weakly dependent on impactor size and impact velocity. For impactors 1 km in diameter or smaller, a hemispherical zone centered on the point of impact contains meter‐scale fragments. For an impactor 1 km in diameter this zone extends to depths of 20 km. At larger impactor  sizes,  overburden  pressure  inhibits  fragmentation  and  only  a  near‐surface  zone  is fragmented. For a 10‐km‐diameter impactor, this surface zone extends to a depthof ~20 km and lateral distances ~300 km from the point of impact. This suggests that impactors from 1 to 10 km in diameter can efficiently fragment the entire lunar crust to depths of ~20 km, implying that much of the modern day megaregolith can be created by single impacts rather than by multiple large impact events.</p> <p>With the extent of in-situ fragmentation examined we turned ourattention to getting our dynamic fragmentation code to run smoothly with iSALE’s PorTens. PorTens is a change made to iSALE to allow for pore space creation in material undergoing tensile stresses and pressures in order to keep thermodynamic consistency. Importantly, wefound that when the two routines are combined, porosity increases substantially, and that the large basins currently observed on the Moon’s surface are likely most responsible for the high porosity detected by the Gravity Recovery and Interior Laboratory (GRAIL) mission. Additionally, we discovered that deep lying porosity seems to be additive, suggesting that even without the influence of the largest impactors it is possible for porosity to increase over time. The final, and possibly most consequential conclusion from this work is the ability of tensile stresses and pressures can create potential sitesof refugia for early life that may have existed on early Earth or possibly Mars.</p> <p>Our final dive into hypervelocity impacts focuses on modeling fragments of ejecta. To study this, we have restructured the original fragmentation code substantially. Because most of the damage occurring in the ejecta is done in shear, our previously used Grady-Kipp implementation is not able to provide any useful data, without first making some necessary changes. Much of shear stresses occurring during the passage of a shockwave is accommodated by ductile deformation. Thus, we allow tensile damage to accumulate independently of any calculated shear damage. This simple assumption allows us to track fragment size within ejecta curtains.We then present the results of fragment size vs velocity for different sized impactors.</p> <p><br></p>

The ultimate goal of this dissertation was to better understand what the Apollo sample collection tells us about the impact history of the Moon. My main research tool is a computer code called Cratered Terrain Evolution Model (CTEM). CTEM is a Monte Carlo landscape evolution code developed to model a planetary surface subjected to impacts. While the main effect of impact cratering that CTEM simulates is elevation changes of the landscape through the excavation process of craters and the deposition of ejecta, I worked to extend the capabilities of the code to study problems in material transport. As impact cratering is a dominant process on the surface of Moon, the stratigraphy of lunar geology is thought to be composed of stacks of impact-generated ejecta layers. Each individual impact generates ejecta that is sourced from varying depths of the subsurface. This ejecta contains a rich abundance of material containing information, including composition and datable impact products, such as impact glasses. The extensions to the CTEM code that I developed allows me to track all ejecta generated during a simulation and model the complex history of the lunar regolith.

This research has involved the conduct of a series of laboratory measurements of the centimeter-wavelength opacity of water vapor along with the development of a hybrid radiative transfer ray-tracing simulator for the atmosphere of Jupiter which employs a model for water vapor opacity derived from the measurements. For this study an existing Georgia Tech high-sensitivity microwave measurement system (Hanley and Steffes , 2007) has been adapted for pressures ranging from 12-100 bars, and a corresponding temperature range of 293-525°K. Water vapor is measured in a mixture of hydrogen and helium. Using these measurements which covered a wavelength range of 6--20 cm, a new model is developed for water vapor absorption under Jovian conditions. In conjunction with our laboratory measurements, and the development of a new model for water vapor absorption, we conduct sensitivity studies of water vapor microwave emission in the Jovian atmosphere using a hybrid radiative transfer ray-tracing simulator. The approach has been used previously for Saturn (Hoffman, 2001), and Venus (Jenkins et al., 2001). This model has been adapted to include the antenna patterns typical of the NASA Juno Mission microwave radiometer (NASA/Juno -MWR) along with Jupiter's geometric parameters (oblateness), and atmospheric conditions. Using this adapted model we perform rigorous sensitivity tests for water vapor in the Jovian atmosphere. This work will directly improve our understanding of microwave absorption by atmospheric water vapor at Jupiter, and improve retrievals from the Juno microwave radiometer. Indirectly, this work will help to refine models for the formation of Jupiter and the entire solar system through an improved understanding of the planet-wide abundance of water vapor which will result from the successful opreation of the Juno Microwave Radiometer (Juno-MWR).

No description available.

This dissertation explores the coupling between radiative and three-dimensional dynamical processes in the atmosphere of Titan, and their impact on the seasonal climate and recent paleoclimate. First, a simple calculation is used to demonstrate the atmospheric attenuation on the distribution of insolation. The maximum diurnal-mean surface insolation does not reach the polar regions in summertime, and this impacts both surface temperatures and their destabilizing effect on the atmosphere. Second, a detailed two-stream, fully non-gray radiative transfer model, written specifically for Titan but with high flexibility, is used to calculate radiative fluxes and the associated heating rates. This model reproduces Titan's temperature structure from the surface through the stratopause, over nearly six decades of pressure. Additionally, a physics parameterizations package is developed for Titan, in part based on similar methods from Earth atmospheric models, for use in a Titan general circulation model (GCM). Simulations with this model, including Titan's methane cycle, reproduce two important observational constraints---Titan's temperature profile and atmospheric superrotation---that have proven difficult to satisfy simultaneously for previous models. Simulations with the observed distribution of seas are used to examine the resulting distribution of cloud activity, atmospheric humidity, and temperatures, and show that these are consistent with dry mid- and low-latitudes, while the observed polar temperatures are reproduced as a consequence of evaporative cooling. Analysis of the surface energy budget shows that turbulent fluxes react to the surface insolation, confirming the importance of its distribution. Finally, the GCM is used to simulate Titan's climate during snapshots over the past 42 kyr that capture the amplitude range of variations in eccentricity and longitude of perihelion. The results show that the atmosphere is largely insensitive to orbital forcing, and that it invariably transports methane poleward, suggesting Titan's low-latitudes have been deserts for at least hundreds of thousands of years. In detail, seasonal asymmetries do affect the distribution of methane, moving methane to the pole with the weaker summer, though orbital variations do not imply a long-period asymmetry. If the timescale for the atmosphere to transport the surface liquid reservoir is sufficiently short, this explains the observed north-south dichotomy of lakes and seas.

abstract: Water is a critical resource for future human missions, and is necessary for understanding the evolution of the Solar System. The Moon and Mars have water in various forms and are therefore high-priority targets in the search for accessible extraterrestrial water. Complementary remote sensing analyses coupled with laboratory and field studies are necessary to provide a scientific context for future lunar and Mars exploration. In this thesis, I use multiple techniques to investigate the presence of water-ice at the lunar poles and the properties of martian chloride minerals, whose evolution is intricately linked with liquid water. Permanently shadowed regions (PSRs) at the lunar poles may contain substantial water ice, but radar signatures at PSRs could indicate water ice or large block populations. Mini-RF radar and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) products were used to assess block abundances where radar signatures indicated potential ice deposits. While the majority of PSRs in this study indicated large block populations and a low likelihood of water ice, one crater – Rozhdestvenskiy N – showed indirect indications of water ice in its interior. Chloride deposits indicate regions where the last substantial liquid water existed on Mars. Major ion abundances and expected precipitation sequences of terrestrial chloride brines could provide context for assessing the provenance of martian chloride deposits. Chloride minerals are most readily distinguished in the far-infrared (45+ μm), where their fundamental absorption features are strongest. Multiple chloride compositions and textures were characterized in far-infrared emission for the first time. Systematic variations in the spectra were observed; these variations will allow chloride mineralogy to be determined and large variations in texture to be constrained. In the present day, recurring slope lineae (RSL) may indicate water flow, but fresh water is not stable on Mars. However, dissolved chloride could allow liquid water to flow transiently. Using Thermal Emission Imaging System (THEMIS) data, I determined that RSL are most likely not fed by chloride-rich brines on Mars. Substantial amounts of salt would be consumed to produce a surface water flow; therefore, these features are therefore thought to instead be surface darkening due to capillary wicking. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2017

abstract: Many planetary science missions study thermophysical properties of surfaces using infrared spectrometers and infrared cameras. Thermal inertia is a frequently derived thermophysical property that quantifies the ability for heat to exchange through planetary surfaces. To conceptualize thermal inertia, the diffusion equation analogies are extended using a general effusivity term: the square root of a product of conductivity and capacity terms. A hypothetical thermal inductance was investigated for diurnal planetary heating. The hyperbolic heat diffusion equation was solved to derive an augmented thermal inertia. The hypothetical thermal inductance was modeled with negligible effect on Mars. Extending spectral performance of infrared cameras was desired for colder bodies in the outer solar system where peak infrared emission is at longer wavelengths. The far-infrared response of an infrared microbolometer array with a retrofitted diamond window was determined using an OSIRIS-REx—OTES interferometer. An instrument response function of the diamond interferometer-microbolometer system shows extended peak performance from 15 µm out to 20 µm and 40% performance to at least 30 µm. The results are folded into E-THEMIS for the NASA flagship mission: Europa Clipper. Infrared camera systems are desired for the expanding smallsat community that can inherit risk and relax performance requirements. The Thermal-camera for Exploration, Science, and Imaging Spacecraft (THESIS) was developed for the Prox-1 microsat mission. THESIS, incorporating 2001 Mars Odyssey—THEMIS experience, consists of an infrared camera, a visible camera, and an instrument computer. THESIS was planned to provide images for demonstrating autonomous proximity operations between two spacecraft, verifying deployment of the Planetary Society’s LightSail-B, and conducting remote sensing of Earth. Prox-1—THESIS was selected as the finalist for the competed University Nanosatellite Program-7 and was awarded a launch on the maiden commercial SpaceX Falcon Heavy. THESIS captures 8-12 µm IR images with 100 mm optics and RGB color images with 25 mm optics. The instrument computer was capable of instrument commanding, automatic data processing, image storage, and telemetry recording. The completed THESIS has a mass of 2.04 kg, a combined volume of 3U, and uses 7W of power. THESIS was designed, fabricated, integrated, and tested in ASU’s 100K clean lab. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23007号 / 理博第4684号 / 新制||理||1672(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 嶺重 慎, 准教授 前田 啓一, 教授 太田 耕司 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Planetary science is often limited to only surface observations of planets requiring the development of modeling techniques to infer information about the planet’s interior. This work outlines three separate scientific problems that arose from planetary surface observations, the methodology utilized to explain the formation of these observation, and what we learned about the planet’s interior by solving these problems. Chapter 1 discusses why lunar mascon basins (impact basins associated with a central freeair gravity positive) form for only a limited range of basin diameters. Modeling the full formation of South-Pole Aitken (SPA) basin using a sequential two-code (hydrocode and Finite Element Model) shows that due to SPA’s great size (long wavelength) and the high geothermal gradient of the Moon at impact, the basin’s relaxation process was controlled by isostatic adjustment with minimal influence from lithospheric rigidity or membrane stresses. Additionally, the modeling shows that the Moon was hot and weak at impact. Chapter 2 addresses why there is a lack of olivine abundance on Mars around large impact basins, and the formation of the megabreccia that is associated with an orthopyroxene signature in the circum-Isidis Planitia region. Hydrocode modeling of the excavation of the Isidis forming impact shows the impact was more than capable of excavating mantle material and reproducing the observed megabreccia. This coupled with the lack of olivine signature indicates that the Martian upper mantle is orthopyroxene-rich. Chapter 3 covers the investigation into why the nitrogen ice sheet on Pluto, Sputnik Planitia, is the youngest observed terrain and why the surface is divided into irregular polygons about 20– 30 kilometers in diameter. The utilization of a new parameterized convection model enables the computation of the Rayleigh number of the nitrogen ice and shows that the nitrogen ice is vigorously convecting, making Rayleigh–Bénard convection the most likely explanation for these polygons (Trowbridge et al., 2016). Additionally, the diameter of Sputnik Planitia’s polygons and the dimensions of its ‘floating mountains’ of water ice suggest that its nitrogen ice is about five to ten kilometers thick (Trowbridge et al., 2016). The estimated convection velocity of 1.5 centimeters a year indicates a surface age of only around a million years (Trowbridge et al., 2016). The accumulation of this work is three chapters that use three separate techniques to further understand three separate planets.