Physical Sciences and Mathematics Commons^™

Observation And Modelling Of Meter-Class Earth Impacting Asteroids, David L. Clark

Electronic Thesis and Dissertation Repository

Earth is constantly bombarded by solar system objects of a wide variety of sizes, from micron-sized meteoroid stream and sporadic meteor dust, to meter-sized and larger meteoroids observed as fireballs. Fireball event characteristics directly point to the properties and structure of the parent body from which the meteoroid originated. In-atmosphere fireball data paired with in-space observations bring much context to both observations. This thesis centres on three published papers that grew out of my Masters project to identify precovery in-space images of meteoroids first observed as fireballs.

The first article describes the first successful identification of an in-space image of …

Physical Dispersions Of Meteor Showers Through High Precision Optical Observations, Denis Vida

Electronic Thesis and Dissertation Repository

Meteoroids ejected from comets form meteoroid streams which disperse over time due to gravitational perturbations and non-gravitational forces. When stream meteoroids collide with the Earth's atmosphere, they are visible as meteors emanating from a common point-like area (radiant) in the sky. Measuring the size of meteor shower radiant areas can provide insight into stream formation and age. The tight radiant dispersion of young streams are difficult to determine due to measurement error, but if successfully measured, the dispersion could be used to constrain meteoroid ejection velocities from their parent comets. The estimated ejection velocity is an uncertain, model-dependent value with …

Quantification Of Surface Roughness Of Lava Flows On Mars, Carolina Rodriguez Sanchez-Vahamonde

Electronic Thesis and Dissertation Repository

Volcanism has played a significant role throughout Mars’ geologic history. Extensive lava flows are widely spread across Mars’ equatorial region, shaping the surface in a very distinct way. In radar images (at the decimeter scale), these flows are bright, which is a typical characteristic of extremely rough, blocky lavas flows seen on Earth. Although the source of the extreme roughness of Martian lava flows is unknown, their surface roughness parameters can be constrained to 1) gain information about Mars’ interior processes, 2) find appropriate analogues on other planetary bodies, and 3) ideally infer the emplacement style of such lavas. Here, …

The Periglacial Landscape Of Mars: Insight Into The 'Decameter-Scale Rimmed Depressions' In Utopia Planitia, Arya Bina

Electronic Thesis and Dissertation Repository

Currently, Mars appears to be in a ‘frozen’ and ‘dry’ state, with the clear majority of the planet’s surface maintaining year-round sub-zero temperatures. However, the discovery of features consistent with landforms found in periglacial environments on Earth, suggests a climate history for Mars that may have involved freeze and thaw cycles. Such landforms include hummocky, polygonised, scalloped, and pitted terrains, as well as ice-rich deposits and gullies, along the mid- to high-latitude bands, typically with no lower than 20o N/S. The detection of near-surface and surface ice via the Phoenix lander, excavation of ice via recent impact cratering activity as …

Impact Melt Emplacement On Mercury, Jeffrey Daniels

Electronic Thesis and Dissertation Repository

Impact cratering is an abrupt, spectacular process that occurs on any world with a solid surface. On Earth, these craters are easily eroded or destroyed through endogenic processes. The Moon and Mercury, however, lack a significant atmosphere, meaning craters on these worlds remain intact longer, geologically. In this thesis, remote-sensing techniques were used to investigate impact melt emplacement about Mercury’s fresh, complex craters. For complex lunar craters, impact melt is preferentially ejected from the lowest rim elevation, implying topographic control. On Venus, impact melt is preferentially ejected downrange from the impact site, implying impactor-direction control. Mercury, despite its heavily-cratered surface, …

Physical Properties Of Faint Meteors Through High-Resolution Observations, Dilini Subasinghe

Electronic Thesis and Dissertation Repository

Small, faint meteors (with masses between 10^-7 and 10^-4 kg) were once part of an asteroid or comet, and collide with Earth's atmosphere daily. Studying meteors is an effective way to survey the physical properties of their parent bodies. Meteor light curves and orbital information is easily obtained from wide-field observations, from which meteoroid structure can be inferred through meteoroid ablation modelling. A high-resolution narrow-field camera can provide much more detail about the poorly understood ablation processes and physical properties of the meteoroid. The goal of this thesis is to better understand the physical properties of meteors using …

Using Bolide Airwaves To Estimate Meteoroid Source Characteristics And Window Damage Potential, Nayeob Gi

Electronic Thesis and Dissertation Repository

We examined the far-field infrasonic signals produced by 78 bolides simultaneously detected by U.S. government sensors to determine the mechanisms responsible for interstation spreads in infrasound signal period. These signal period spreads lead to large variances in source energy estimates. Our analysis suggests that while acoustic source height contributes to some extent to the variance in signal periods, the range from the source to the station and in particular station noise plays a more significant role.

By simulating the near-field weak shocks from a suite of well-observed energetic fireballs, we have empirically estimated how often fireball shocks produce overpressure ( …

Formation And Past Evolution Of The Meteoroid Complex Of Comet 96p/Machholz, Abedin Yusein Abedin

Electronic Thesis and Dissertation Repository

The past dynamical evolution of the meteoroid streams associated with comet 96P/Machholz is investigated. The goal is to obtain a coherent picture of the past capture of this large comet into a short period orbit, and its subsequent breakup hierarchy. In particular, the aim is to constrain the earliest epoch that this large first precursor started to supply meteoroids into the interplanetary space. The fragments and meteoroid streams of that past cometary decay constitute a wide multiplex of interplanetary bodies, knows as the 96P/Machholz complex. The largest presently surviving fragment is comet 96P/Machholz, followed by a large amount of debris …

Aging Comets And Their Meteor Showers, Quanzhi Ye

Electronic Thesis and Dissertation Repository

Comets are thought to be responsible for the terrestrial accretion of water and organic materials. Comets evolve very quickly, and will generally deplete their volatiles in a few hundred revolutions. This process, or the aging of comets, is one of the most critical yet poorly understood problems in planetary astronomy. The goal of this thesis is to better understand this problem by examining different parts of the cometary aging spectrum of Jupiter-family comets (JFCs), a group of comets that dominates the cometary influx in the near-Earth space, using both telescopic and meteor observations. We examine two representative JFCs and the …

Automated Image Interpretation For Science Autonomy In Robotic Planetary Exploration, Raymond Francis

Electronic Thesis and Dissertation Repository

Advances in the capabilities of robotic planetary exploration missions have increased the wealth of scientific data they produce, presenting challenges for mission science and operations imposed by the limits of interplanetary radio communications. These data budget pressures can be relieved by increased robotic autonomy, both for onboard operations tasks and for decision- making in response to science data.

This thesis presents new techniques in automated image interpretation for natural scenes of relevance to planetary science and exploration, and elaborates autonomy scenarios under which they could be used to extend the reach and performance of exploration missions on planetary surfaces.

Two …

A Multispectral Assessment Of Complex Impact Craters On The Lunar Farside, Bhairavi Shankar

Electronic Thesis and Dissertation Repository

Hypervelocity collisions of asteroids onto planetary bodies have catastrophic effects on the target rocks through the process of shock metamorphism. The resulting features, impact craters, are circular depressions with a sharp rim surrounded by an ejecta blanket of variably shocked rocks. With increasing impact energy, the inner crater cavity can preserve complex morphologies including terraced walls, central uplifts, and melted rocks. The lack of erosion due to the absence of water or an atmosphere makes the Moon the perfect target to study impact crater processes, in particular the distribution of highly shocked materials within impact craters of different sizes. …

Bulk Density Of Small Meteoroids, Jean-Baptiste Kikwaya Eluo

Electronic Thesis and Dissertation Repository

The purpose of our work is to determine the bulk density of meteoroids. Unlike previous works which focused either on the dynamical properties of the meteoroids (deceleration), ignoring fragmentation; or on fitting solely the lightcurves, neglecting the dynamics of the meteoroids, we use both the photometry and astrometry to constrain our model. Our model, based on the dustball model, considers the meteoroid to be a collection of grains held together by a lower boiling point 'glue'. It uses conservation of energy and momentum to model the change in velocity and the light production as a function of time. The free …