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Title: FREQUENCY DISTRIBUTION OF PYROXENE TYPES AND A METHOD TO SEPARATE THE COMPOSITION OF MULTIPLE PYROXENES IN A SAMPLE.
Creator: Davis, Jimmy, Britt, Daniel, University of Central Florida
Abstract / Description: Determining mafic mineral composition of asteroid bodies is a topic reviewed by M.J. Gaffey et al. (2002). The iterative procedure discussed can be implemented as an algorithm, and such efforts revealed weaknesses that are examined in this work. We seek to illustrate the limits of this method and graphically determine its predictions. There are boundaries in the formulae given where the equations break down. In ranges where mafic mixtures are predicted, a method is illustrated that allows a...
Show moreDetermining mafic mineral composition of asteroid bodies is a topic reviewed by M.J. Gaffey et al. (2002). The iterative procedure discussed can be implemented as an algorithm, and such efforts revealed weaknesses that are examined in this work. We seek to illustrate the limits of this method and graphically determine its predictions. There are boundaries in the formulae given where the equations break down. In ranges where mafic mixtures are predicted, a method is illustrated that allows a decoupling of these mixtures into the constituents.
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Date Issued: 2007
Identifier: CFE0001922, ucf:47493
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001922

Title: SURVEY OF METEORITE PHYSICAL PROPERTIES: DENSITY, POROSITY AND MAGNETIC SUSCEPTIBILITY.
Creator: Macke, Robert, Britt, Daniel, University of Central Florida
Abstract / Description: The measurement of meteorite physical properties (i.e. density, porosity, magnetic susceptibility) supplements detailed chemical and isotopic analyses for small samples (thin sections or ~300 mg portions) by providing whole-rock data for samples massing in the tens of grams. With the advent of fast, non-destructive and non-contaminating measurement techniques including helium ideal-gas pycnometry for grain density, the Archimedean Ã‚Â"glass beadÃ‚Â" method...
Show moreThe measurement of meteorite physical properties (i.e. density, porosity, magnetic susceptibility) supplements detailed chemical and isotopic analyses for small samples (thin sections or ~300 mg portions) by providing whole-rock data for samples massing in the tens of grams. With the advent of fast, non-destructive and non-contaminating measurement techniques including helium ideal-gas pycnometry for grain density, the Archimedean Ã‚Â"glass beadÃ‚Â" method for bulk density and (with grain density) porosity, and the use of low-field magnetometry for magnetic susceptibility, all of which rely on compact and portable equipment, this has enabled a comprehensive survey of these physical properties for a wide variety of meteorites. This dissertation reports on the results of that survey, which spanned seven major museum and university meteorite collections as well as the Vatican collection. Bulk and grain densities, porosities and magnetic susceptibilities are reported for 1228 stones from 664 separate meteorites, including several rare meteorite types that are underrepresented in previous studies. Summarized here are data for chondrites (carbonaceous, ordinary and enstatite) and stony achondrites. Several new findings have resulted from this study. From the use of a Ã‚Â"weathering modulusÃ‚Â" based on grain density and magnetic susceptibility to quantify weathering in finds, it is observed that the degree of weathering of ordinary chondrites is dependent on their initial porosity, which becomes reduced to less than ~8% for all finds, but for enstatite chondrites weathering actually increases porosity. Grain density and magnetic susceptibility, which have been shown to distinguish H, L and LL ordinary chondrites, also may distinguish shergottites, nakhlites and chassignites from each other, but the two groups of enstatite chondrites (EH and EL) remain indistinguishable in these properties. H chondrite finds exhibit a slight negative trend in porosity with increasing petrographic type, and all chondrite falls together exhibit a pronounced negative trend in porosity spanning all petrographic types. The overall trend corresponds roughly to a positive trend in porosities with respect to both degree of oxidation and percentage of matrix. It also corresponds to the macroporosities of analogous asteroids. These traits constrain models of conditions in the solar nebula and the formation of chondrite parent-body precursors.
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Date Issued: 2010
Identifier: CFE0003424, ucf:48420
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003424

Title: Investigating compositional variations of S-complex near-Earth asteroids: (1627) Ivar.
Creator: Jones, Jenna, Fernandez, Yan, Britt, Daniel, Campins, Humberto, Howell, Ellen, University of Central Florida
Abstract / Description: We seek to investigate the complexity and heterogeneity of the surfaces of near-Earth asteroids (NEAs). In particular, we are studying the S-complex NEAs, which account for a large portion of the observed near-Earth objects. Here we present our results for (1627) Ivar, an Amor class NEA with taxonomic type Sqw. In 2013, Ivar's large size and close approach to Earth (minimum distance 0.32 AU) provided an opportunity to observe the asteroid over many different viewing angles for an extended...
Show moreWe seek to investigate the complexity and heterogeneity of the surfaces of near-Earth asteroids (NEAs). In particular, we are studying the S-complex NEAs, which account for a large portion of the observed near-Earth objects. Here we present our results for (1627) Ivar, an Amor class NEA with taxonomic type Sqw. In 2013, Ivar's large size and close approach to Earth (minimum distance 0.32 AU) provided an opportunity to observe the asteroid over many different viewing angles for an extended period of time. We collected delay-Doppler radar images and Doppler spectra using the Arecibo Observatory's 2380 MHz radar, and, by incorporating an extensive lightcurve collection, we have constrained the shape and spin state. In addition, we observed Ivar using NASA's IRTF's SpeX mode to gather rotationally resolved reflected and thermal spectra in the near-IR regime. We have created a high-resolution shape model, and we have found Ivar to have a sidereal period of 4.7951689 (&)#177; 0.0000026 hours with a pole at ecliptic longitude and latitude 336(&)deg;, +37(&)deg; ((&)#177; 6(&)deg;) respectively. We also show that Ivar is more elongated than previous studies suggests, with dimensions along the principal axis 15.15 x 6.25 x 5.66 (&)#177; 10%. This model has been incorporated into our thermal modeling code, SHERMAN, in order to determine which reflective, thermal, and surface properties best reproduce our numerous and rotationally resolved spectra. Primarily, we vary thermal inertia, geometric albedo, and crater fraction (surface roughness) although SHERMAN has many parameters that are allowed to vary. Our findings show that Ivar's thermal observations cannot be reproduced with a homogeneous model, but rather a heterogeneous model with a thermal inertia spot, and possibly different crater fraction values, needs to be applied in order to reproduce all of the spectra. Due to the variations in observing geometry for our thermal spectra, the properties of this spot are well constrained. We find that, with this spot, that the values of thermal inertia, geometric albedo, and crater fraction are 80 (&)#177; 20 J m-2 s-1/2 K-1, 0 (-) 0.3, and 0.27 (&)#177; 0.02, respectively. This work shows the advantage of having many datasets for deep study of an individual NEA, and with these results, we will learn more about the detailed regolith and surface properties of Ivar and how those properties compare to those of other NEAs.
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Date Issued: 2018
Identifier: CFE0007022, ucf:52044
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007022

Title: Determining the Small-scale Structure and Particle Properties in Saturn's Rings from Stellar and Radio Occultations.
Creator: Jerousek, Richard, Colwell, Joshua, Britt, Daniel, Fernandez, Yan, Hedman, Mathew, University of Central Florida
Abstract / Description: Saturn's rings consist of icy particles of various sizes ranging from millimeters to several meters. Particles may aggregate into ephemeral elongated clumps known as self-gravity wakes in regions where the surface mass density and epicyclic frequency give a Toomre critical wavelength which is much larger than the largest individual particles (Julian and Toomre 1966). Optical depth measurements at different wavelengths can be used to constrain the sizes of individual particles (Zebker et al....
Show moreSaturn's rings consist of icy particles of various sizes ranging from millimeters to several meters. Particles may aggregate into ephemeral elongated clumps known as self-gravity wakes in regions where the surface mass density and epicyclic frequency give a Toomre critical wavelength which is much larger than the largest individual particles (Julian and Toomre 1966). Optical depth measurements at different wavelengths can be used to constrain the sizes of individual particles (Zebker et al. 1985, Marouf et al. 1983) while measurements of optical depths spanning many viewing geometries can be used to determine the properties of self-gravity wakes (Colwell et al. 2006, 2007, Hedman et al. 2007, Nicholson and Hedman 2010, Jerousek et al. 2016). Studies constraining the parameters of the assumed power-law particle size distribution have been attempted (Zebker et al. 1985, Marouf et al. 1983) but have not yet accounted for the presence of self-gravity wakes or the much larger elongated particle aggregates seen in Cassini Imaging Subsystem (ISS) images and commonly referred to as (")straw("). We use a multitude of Cassini stellar occultations measured by UVIS (Ultraviolet Imaging Spectrograph) and VIMS (Visual and Infrared Mapping Spectrometer) together with Cassini's RSS (Radio Science Sub System) X-band, Ka-band, and S-band radio occultations to better constrain the particle size distribution throughout Saturn's main ring system, including regions where self-gravity wakes have a significant effect on the measured optical depth of the rings.
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Date Issued: 2018
Identifier: CFE0007019, ucf:52029
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007019

Title: Asteroid Surfaces: The Importance of Cohesive Forces.
Creator: Jardine, Keanna, Dove, Adrienne, Tetard, Laurene, Britt, Daniel, University of Central Florida
Abstract / Description: Adhesive forces play a significant role on airless bodies due to their weak gravities. Investigating adhesion at the surface of asteroids and their constituent components is vital to understanding their formation and evolution. Previous research has been done to understand the interaction of micron-sized spheres to planar surfaces and sphere-to-sphere interactions, which have been used to develop models of asteroid surfaces. Our investigation experimentally investigates adhesion through...
Show moreAdhesive forces play a significant role on airless bodies due to their weak gravities. Investigating adhesion at the surface of asteroids and their constituent components is vital to understanding their formation and evolution. Previous research has been done to understand the interaction of micron-sized spheres to planar surfaces and sphere-to-sphere interactions, which have been used to develop models of asteroid surfaces. Our investigation experimentally investigates adhesion through atomic force microscopy (AFM) measurements between JSC-1 simulant particles and several AFM tips, including a typical pyramidal gold tip and microspheres of sizes 2 (&)#181;m and 15 (&)#181;m. The samples of JSC-1 consist of three size ranges: (<) 45 (&)#181;m, 75-125 (&)#181;m, and 125-250 (&)#181;m. For each sample we looked at the magnitude and distribution of the measured adhesive forces. Results show that the pyramidal tip produced larger forces than the spherical tips generally, and the sample that produced larger forces and a larger distribution of those force was the smaller, more powder-like sample with sizes (<)45 (&)#181;m.
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Date Issued: 2018
Identifier: CFE0007755, ucf:52377
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007755

Title: Analysis of Nucleus Properties of the Enigmatic Comet 29P/Schwassmann-Wachmann 1.
Creator: Schambeau, Charles, Fernandez, Yan, Britt, Daniel, Kokoouline, Viatcheslav, Samarasinha, Nalin, University of Central Florida
Abstract / Description: We present results from a continuing effort to understand activity drivers for the enigmatic Comet 29P/Schwassmann-Wachmann 1 (SW1). SW1 has been of interest since its discovery almost 100 years ago because of its nearly continuous, quiescent activity beyond the water-sublimation line and its highly variable, outburst activity while receiving a nearly constant insolation due to its low eccentricity orbit. These characteristics make SW1 a useful target for investigating both distant cometary...
Show moreWe present results from a continuing effort to understand activity drivers for the enigmatic Comet 29P/Schwassmann-Wachmann 1 (SW1). SW1 has been of interest since its discovery almost 100 years ago because of its nearly continuous, quiescent activity beyond the water-sublimation line and its highly variable, outburst activity while receiving a nearly constant insolation due to its low eccentricity orbit. These characteristics make SW1 a useful target for investigating both distant cometary activity drivers and also cometary outburst behavior. We approach answering these ques- tions through a detailed analysis of SW1; first by measuring nucleus properties required for a more accurate nucleus thermophysical modeling and second, by applying thermal modeling to replicate its activity. Our project began with an analysis of Spitzer Space Telescope infrared observations of SW1 from 2003. Coma removal techniques when applied to the images provided nucleus photometry measurements. Application of the Near Earth Asteroid Thermal Model (NEATM) to these measured photometry values resulted in an effective nucleus radius of 32.3 (&)#177; 3.1 km and a thermal beaming parameter of 1.14 (&)#177;0.22. These results indicated that SW1 is one of the largest Jupiter Family Comets and also has a relatively smooth overall surface and/or a low thermal inertia. We next placed constraints on the nucleus' spin state through analysis of evolution seen in the coma's morphological structure through two sets of outburst coma observations. The first set analyzed are from the Kitt Peak 2.1-m telescope taken ~2 days after a major outburst in 2008. 3-D Monte Carlo coma modeling showed that the nucleus' spin period is on the order of days and/or the spin pole orientation was along the Earth's directions during observations. The second set are Hubble Space Telescope observations from 1996 taken ~15 hours after a major outburst. Modeling similarly showed a rotation period on the order of days. Due to the observing geometry differing between the 2008 and 1996 observations, we conclude the rotation period lower limit must be on the order of days even if the spin-pole direction was directed along the sub-Earth direction during one set of observations. The nucleus properties measured or constrained by our project were incorporated into a thermophysical model to replicate the quiescent activity via the sublimation of the supervolatile species CO or CO2. A progenitor nucleus was thermally evolved in SW1's current orbit using different plausible nucleus interior compositional and layering schemes. We discuss results of this analysis and additionally possibilities for future thermal modeling efforts.
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Date Issued: 2018
Identifier: CFE0007585, ucf:52548
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007585

Title: Characterization of online archives of astronomical imaging vis-(&)#224;-vis serendipitous asteroids, and their astrometric properties.
Creator: Denis, Jean-Marc, Fernandez, Yanga, Britt, Daniel, Schelling, Patrick, University of Central Florida
Abstract / Description: The identification of known asteroids on existing CCD pictures would allow us to obtain accurate astrometric and photometric asteroid properties. Some asteroids might have ambiguous orbital elements, thus their identification along with their exact positions on multiple picture frames could significantly improve their orbital elements. Furthermore, the possibility of identifying known asteroids on older pictures, sometimes preceding their discovery date, might allow the study of non...
Show moreThe identification of known asteroids on existing CCD pictures would allow us to obtain accurate astrometric and photometric asteroid properties. Some asteroids might have ambiguous orbital elements, thus their identification along with their exact positions on multiple picture frames could significantly improve their orbital elements. Furthermore, the possibility of identifying known asteroids on older pictures, sometimes preceding their discovery date, might allow the study of non-gravitational effects like the Yarkovsky effect.Identifying a potential Yarkovsky effect on asteroids is challenging because it is extremely weak. However, this effect cumulates with time, therefore, it is necessary to find astronomical pictures that are as old as possible. In addition, we need to collect high quality CCD pictures and use a methodology that would allow obtaining a statistically significant sample of asteroids. To accomplish this, we decided to use the online archive of the Subaru telescope at Mauna Kea Hawaii because it has a prime-focus camera with a very high resolution of 80 millions pixels very well suited to capture serendipitous asteroids. In addition, the Subaru online archive has pictures from the last 10 years.The methodology used in this thesis is to build a database that contains the orbital elements of all the known asteroids, allowing us to write a program that calculates the approximate position of all the asteroids at the date and time of each CCD picture we collect. To obtain a more precise position, the program also interfaces the JPL NASA Horizons on-line computation service. Every time an asteroid is found on a picture, Horizons sends its theoretical location back to the program. A later visual identification of this asteroid at this theoretical location on the picture triggers its input into our sample for further study. This method allowed us to visually confirm 508 distinct asteroids on 692 frames with an average diameter of 3.6 km. Finally, we use the theory (given in appendix A) to calculate the theoretical drift of these asteroids that we compare with the one we measured on the CCD pictures.
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Date Issued: 2012
Identifier: CFE0004299, ucf:49460
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004299

Title: Chemistry and dissipation at mineral surfaces in the space environment.
Creator: Tucker, William, Schelling, Patrick, Britt, Daniel, Kara, Abdelkader, Coffey, Kevin, University of Central Florida
Abstract / Description: The composition and morphology of mineral surfaces is known to play an important role in various phenomena relevant to planetary science. For example, the synthesis and processing of complex organics likely occurs at mineral surfaces strongly affected by the space environment. Furthermore, the dissipative and adhesive properties of dust grains may depend strongly on the chemical state of the surface including the presence of dangling bonds, adsorbates, and radicals. In this dissertation,...
Show moreThe composition and morphology of mineral surfaces is known to play an important role in various phenomena relevant to planetary science. For example, the synthesis and processing of complex organics likely occurs at mineral surfaces strongly affected by the space environment. Furthermore, the dissipative and adhesive properties of dust grains may depend strongly on the chemical state of the surface including the presence of dangling bonds, adsorbates, and radicals. In this dissertation, experimental results are first presented which demonstrate that mineral grains subjected to high temperatures in a reducing environment lead to iron nanoparticles which are strongly catalytic for the formation of complex organic species. Next, results obtained using molecular-dynamics simulations demonstrate that uncoordinated surface atoms in metallic nanoparticles result in plastic deformation, strong dissipation and adhesion during collisions. This can be contrasted with previous simulations which demonstrate significantly weaker dissipation when surface atoms are passivated. Calculations of critical sticking velocities demonstrate that simple coarse- grain models are insufficient for predicting the adhesive behavior of sub-micron sized grains. Next, results are presented describing a computational study illuminating the role of surface chemistry on adhesion and dissipation for iron nanoparticle collisions, which in the case of free radical adsorbates may also contribute to the creation of more complex species. Lastly, to further elucidate dissipation, the direct coupling of harmonic vibrational modes in the dissipation process is established. The results demonstrate broad participation of low and high-frequency modes during a collision during a timescale less than time required for particles to rebound. Hence, our results demonstrate extremely strong likelihood of adhesion during collisions. This approach provides a way to use density-functional theory calculations to directly compute dissipative couplings at mineral interfaces.
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Date Issued: 2019
Identifier: CFE0007545, ucf:52592
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007545

Title: Observations, Thermochemical Calculations, and Modeling of Exoplanetary Atmospheres.
Creator: Blecic, Jasmina, Harrington, Joseph, Britt, Daniel, Peale, Robert, Fortney, Jonathan, University of Central Florida
Abstract / Description: This dissertation as a whole aims to provide the means to better understand hot-Jupiter planets through observing, performing thermochemical calculations, and modeling their atmospheres. We used Spitzer multi-wavelength secondary-eclipse observations to characterize planetary atmospheres. We chose targets with high signal-to-noise ratios, as their deep eclipses allow us to detect signatures of spectral features and assess planetary atmospheric structure and composition with greater certainty....
Show moreThis dissertation as a whole aims to provide the means to better understand hot-Jupiter planets through observing, performing thermochemical calculations, and modeling their atmospheres. We used Spitzer multi-wavelength secondary-eclipse observations to characterize planetary atmospheres. We chose targets with high signal-to-noise ratios, as their deep eclipses allow us to detect signatures of spectral features and assess planetary atmospheric structure and composition with greater certainty. Chapter 1 gives a short introduction. Chapter 2 presents the Spitzer secondary-eclipse analysis and atmospheric characterization of WASP-14b. The decrease in flux when a planet passes behind its host star reveals the planet dayside thermal emission, which, in turn, tells us about the atmospheric temperature and pressure profiles and molecular abundances. WASP-14b is a highly irradiated, transiting hot Jupiter. By applying a Bayesian approach in the atmospheric analysis, we found an absence of thermal inversion contrary to theoretical predictions. Chapter 3 describes the infrared observations of WASP-43b's Spitzer secondary eclipses, data analysis, and atmospheric characterization. WASP-43b is one of the closest-orbiting hot Jupiters, orbiting one of the coolest stars with a hot Jupiter. This configuration provided one of the strongest signal-to-noise ratios. The atmospheric analysis ruled out a strong thermal inversion in the dayside atmosphere of WASP-43b and put a nominal upper limit on the day-night energy redistribution. Chapter 4 presents an open-source Thermochemical Equilibrium Abundances (TEA) code and its application to several hot-Jupiter temperature and pressure models. TEA calculates the abundances of gaseous molecular species using the Gibbs free-energy minimization method within an iterative Lagrangian optimization scheme. The thermochemical equilibrium abundances obtained with TEA can be used to initialize atmospheric models of any planetary atmosphere. The code is written in Python, in a modular fashion, and it is available to the community via http://github.com/dzesmin/TEA. Chapter 5 presents my contributions to an open-source Bayesian Atmospheric Radiative Transfer (BART) code, and its application to WASP-43b. BART characterizes planetary atmospheres based on the observed spectroscopic information. It initializes a planetary atmospheric model, performs radiative-transfer calculations to produce models of planetary spectra, and using a statistical module compares models with observations. We describe the implementation of the initialization routines, the atmospheric profile generator, the eclipse module, the best-fit routines, and the contribution function module. We also present a comprehensive atmospheric analysis of all WASP-43b secondary-eclipse data obtained from the space- and ground-based observations using BART.
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Date Issued: 2015
Identifier: CFE0005926, ucf:50841
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005926

Title: Synchrotron based infrared microspectroscopy of carbonaceous chondrites.
Creator: Yesiltas, Mehmet, Peale, Robert, Fernandez, Yan, Britt, Daniel, Reach, William, University of Central Florida
Abstract / Description: Relationships between organic molecules and inorganic minerals are investigated in five carbonaceous chondrites, Northwest Africa 852 (CR2), Tagish Lake (C2-ungroupped), Orgueil (CI1), Sutter's Mill (CM), and Murchison (CM2), with micron spatial resolution using synchrotron-based imaging micro-FTIR spectroscopy. Correlations based on absorption strength for various constituents are determined using statistical correlation analysis. Silicate band is found to be positively correlated with...
Show moreRelationships between organic molecules and inorganic minerals are investigated in five carbonaceous chondrites, Northwest Africa 852 (CR2), Tagish Lake (C2-ungroupped), Orgueil (CI1), Sutter's Mill (CM), and Murchison (CM2), with micron spatial resolution using synchrotron-based imaging micro-FTIR spectroscopy. Correlations based on absorption strength for various constituents are determined using statistical correlation analysis. Silicate band is found to be positively correlated with stretching modes of aliphatic hydrocarbons in NWA 852 and Tagish Lake. The former is highly correlated with the hydration band in all meteorites. Negative correlation is observed between water+organics and carbonate bands in all meteorites. Two dimensional infrared maps for NWA 852 and Orgueil show that carbonates are spatially separated from water+organic combination, silicates, OH, and CH distributions. Overlapping of the latter three in NWA 852 and Tagish Lake suggests a possible catalytic role of phyllosilicates in the formation of organics. Additionally, spectroscopic analyses on Sutter's Mill meteorite fragments present multiple distinct mineralogies. Spatial and spectral evidences on this regolith breccia suggest mixing of multiple parent bodies. Ratios of asymmetric CH2 and CH3 band strengths for NWA 852, Tagish Lake, and Sutter's Mill are similar to the average ratio of interplanetary dust particles and Wild 2 cometary dust particles, however significantly exceeds that of interstellar medium objects and several aqueously altered carbonaceous chondrites such as Orgueil. This suggests distinct formation regions and/or parent body processing of organics for these meteorites. Our infrared spectro-microtomography measurements on Murchison meteorite, representing the first such measurement on any kind of meteorite, comprise of three-dimensional reconstructions of specific molecular functional groups for understanding the spatial distributions of these groups.
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Date Issued: 2015
Identifier: CFE0006061, ucf:50966
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006061

Title: Creation and Application of Routines for Determining Physical Properties of Asteroids and Exoplanets from Low Signal-To-Noise Data Sets.
Creator: Lust, Nathaniel, Britt, Daniel, Fernandez, Yan, Pensky, Marianna, Harris, Alan, University of Central Florida
Abstract / Description: Astronomy is a data heavy field driven by observations of remote sources reflecting or emitting light. These signals are transient in nature, which makes it very important to fully utilize every observation. This however is often difficult due to the faintness of these observations, often are only slightly above the level of observational noise. We present new or adapted methodologies for dealing with these low signal-to-noise scenarios, along with practical examples including determining...
Show moreAstronomy is a data heavy field driven by observations of remote sources reflecting or emitting light. These signals are transient in nature, which makes it very important to fully utilize every observation. This however is often difficult due to the faintness of these observations, often are only slightly above the level of observational noise. We present new or adapted methodologies for dealing with these low signal-to-noise scenarios, along with practical examples including determining exoplanet physical properties, periodicities in asteroids, and the rotational and orbital properties of the multiple asteroid system 2577 Litva.
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Date Issued: 2014
Identifier: CFE0005523, ucf:50307
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005523

Title: Spectral Study of Asteroids and Laboratory Simulated Asteroid Organics.
Creator: Hargrove, Kelsey, Colwell, Joshua, Fernandez, Yan, Britt, Daniel, Kelley, Michael, University of Central Florida
Abstract / Description: We investigate the spectra of asteroids at near- and mid-infrared wavelengths. In 2010 and 2011 we reported the detection of 3 ?m and 3.2-3.6 ?m signatures on (24) Themis and (65) Cybele indicative of water-ice and complex organics [1] [2] [3]. We further probed other primitive asteroids in the Cybele dynamical group and Themis family, finding diversity in the shape of their 3 ?m [4] [5] [6] and 10 ?m spectral features [4]. These differences indicated mineralogical and compositional...
Show moreWe investigate the spectra of asteroids at near- and mid-infrared wavelengths. In 2010 and 2011 we reported the detection of 3 ?m and 3.2-3.6 ?m signatures on (24) Themis and (65) Cybele indicative of water-ice and complex organics [1] [2] [3]. We further probed other primitive asteroids in the Cybele dynamical group and Themis family, finding diversity in the shape of their 3 ?m [4] [5] [6] and 10 ?m spectral features [4]. These differences indicated mineralogical and compositional variations within these asteroid populations. Also in the mid-infrared region we studied a larger population of asteroids belonging to the Bus C, D, and S taxanomic classes to understand the relationship between any mineralogy and hydration inferred in the visible and near- infrared with the shape, strength, and slope of the 10 ?m emission. We have discovered that at least 3 of the main Bus taxanomic groups (Cs, Ds, and Ss as defined by their visible spectra) clearly cluster into 3 statistically distinct groups based on their 8-13 ?m spectra. Additionally we have attempted to simulate in a laboratory the possible organic compounds we have detected on two asteroids, using various mixtures containing aromatic and aliphatic hydrocarbons. We find that asteroid (24) Themis and (65) Cybele have ?CH2/?CH3 and NCH2/NCH3 ratios similar to our 3- methylpentane, propane, and hexane residues, suggesting that the organics on these asteroids may be short chained and/or highly branched. The ?CH2/?CH3 and NCH2/NCH3 for asteroid(24)Themis are most consistent with the DISM, and some carbonaceous chondrites. The band centers of the C-H stretch absorptions indicate that both asteroids may have aliphatic carriers chemically bonded to electronegative groups (i.e. aromatics), and some that are not. We also detect a 3.45 ?m feature in the spectra of both asteroids that is present in several dense molecular clouds. Our results suggest an interstellar origin for the organics on (24) Themis, and likely (65) Cybele. The differences in the organics of Themis and Cybele are likely related to variations in thermal processing, irradiation and/or formation region in the solar nebula.
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Date Issued: 2015
Identifier: CFE0005624, ucf:50201
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005624

Title: The physical properties and composition of main-belt asteroids from infrared spectroscopy.
Creator: Landsman, Zoe, Campins, Humberto, Britt, Daniel, Fernandez, Yan, Emery, Joshua, Hernandez, Florencio, University of Central Florida
Abstract / Description: Asteroids are the remnants of planet formation, and as such, they represent a record of the physical and chemical conditions in the early solar system and its evolution over the past 4.6 billion years. Asteroids are relatively accessible by spacecraft, and thus may be a source of the raw materials necessary for future human exploration and settlement of space. Those on Earth-crossing orbits pose impact hazards for which mitigation strategies must be developed. For these reasons, several...
Show moreAsteroids are the remnants of planet formation, and as such, they represent a record of the physical and chemical conditions in the early solar system and its evolution over the past 4.6 billion years. Asteroids are relatively accessible by spacecraft, and thus may be a source of the raw materials necessary for future human exploration and settlement of space. Those on Earth-crossing orbits pose impact hazards for which mitigation strategies must be developed. For these reasons, several missions to asteroids are in progress or planned with the support of the National Aeronautics and Space Administration (NASA) and other national space agencies. The study of asteroid composition and physical surface properties is vital to both our scientific understanding of the solar system's formation and evolution and to the development of asteroid missions and resource utilization schemes. This dissertation uses infrared spectroscopy to investigate the composition and physical properties of main-belt asteroid surfaces. Our efforts are focused on two populations that are especially relevant to constraining thermal and collisional processes in the asteroid belt: the "M-type" asteroids and primitive asteroid families.To investigate volatiles in the M-type asteroids, we obtained 2-4 micron spectra of six M-type asteroids using NASA's Infrared Telescope Facility. We find spectral signatures of hydrated minerals on all six asteroids, with evidence for rotational variability of hydration in one target. Diversity in the shape of the 3-micron feature in our sampled asteroids suggests there are different modes of hydration in the M-type population. Next, we carried out a thermal and compositional study of M-type asteroid (16) Psyche using 5-14 micron spectra from the Spitzer Space Telescope. Psyche is suspected to be a remnant iron core, and it is the target of an upcoming NASA mission. Using thermophysical modeling, we find that Psyche's surface is smooth and most likely has a thermal inertia of 5-25 J/m^2/K/s^(1/2), and a bolometric emissivity of 0.9, although a scenario with an emissivity of 0.7 and thermal inertia up to 95 J/m^2/K/s^(1/2) is possible if Psyche is somewhat larger than previously determined. From comparisons with laboratory spectra of silicate and meteorite powders, Psyche's emissivity spectrum is consistent with the presence of fine-grained ((<)75 micron) silicates. These silicates may include a magnesian pyroxene component. We conclude that Psyche is likely covered in a fine silicate regolith, which may also contain iron grains, overlying an iron-rich bedrock.Finally, we compared the mid-infrared properties of two primitive asteroids families, ancient Themis (~2.5 Gyr) and young Veritas (~8 Myr). Visible and near-infrared studies show spectral differences between the two families attributed to different degrees of space weathering. To test whether these differences are apparent in the mid-infrared, we analyzed the 5-14 micron Spitzer Space Telescope spectra of 11 Themis-family asteroids and 9 Veritas-family asteroids. We detect a broad 10-micron emission feature, attributed to fine-grained and/or porous silicate regolith, in all 11 Themis-family spectra and six of nine Veritas-family asteroids, with 10-micron spectral contrast ranging from 1% +/- 0.1% to 8.5% +/- 0.9%. Comparison with laboratory spectra of primitive meteorites suggests these asteroids are similar to meteorites with relatively low abundances of phyllosilicates. We used thermal modeling to derive diameters, beaming parameters and albedos for our sample. Asteroids in both families have beaming parameters near unity and geometric albedos in the range 0.031-0.14. Spectral contrast of the 10-micron silicate emission feature is not correlated with asteroid diameter; however, higher 10-micron contrast may be associated with flatter spectral slopes in the near-infrared. There is a slight trend of increasing 10-micron contrast with decreasing albedo in the Veritas asteroids, but not the Themis asteroids. Overall, our results indicate the Themis and Veritas family members show variation in regolith texture and/or structure within both families that is not directly related to family age.
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Date Issued: 2017
Identifier: CFE0007124, ucf:51966
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007124

Title: Atomic-scale simulation of physical and chemical processes during space weathering and planet formation.
Creator: Quadery, Abrar, Schelling, Patrick, Britt, Daniel, Peale, Robert, Kara, Abdelkader, Sohn, Yongho, University of Central Florida
Abstract / Description: We investigate the mechanisms of space weathering and dust grain collisions, two topics of interests from planetary sciences, using atomic-scale simulations. Space weathering is the change in chemical and physical properties of minerals exposed to solar radiation and micrometeorite bombardment on surfaces of airless planetary bodies like the Moon and asteroids. An understanding of the connection between the surface evolution of the minerals and the underlying thermodynamic and kinetic factors...
Show moreWe investigate the mechanisms of space weathering and dust grain collisions, two topics of interests from planetary sciences, using atomic-scale simulations. Space weathering is the change in chemical and physical properties of minerals exposed to solar radiation and micrometeorite bombardment on surfaces of airless planetary bodies like the Moon and asteroids. An understanding of the connection between the surface evolution of the minerals and the underlying thermodynamic and kinetic factors is still missing. We address this issue and determine the time evolution of Frenkel defects in the silicate minerals olivine ((Mg,Fe)$_2$SiO$_4$) and orthopyroxene ((Mg,Fe)SiO$_3$) using molecular dynamics with a pair potential. Defect diffusion and clustering are observed in both the minerals. Cation diffusion occurs more readily in olivine than in orthopyroxene and leads to faster annealing in the former. In orthopyroxene, diffusion of anion defects, especially oxygen interstitials, occurs more rapidly and also exhibits anisotropy, which hinders the annealing process. This difference in defect evolution may explain the experimental observation that surface modifications due to irradiation is more pronounced in orthopyroxene than in olivine. Dust grain collision is the dominant process in the initial stage of planet formation, however, the mechanisms by which dust grains grow to larger aggregates and eventually to kilometer sized planetesimal is still not understood. We explore the role of surface chemistry in energy dissipation and grain adhesion during collision of amorphous silica (SiO$_2$) nanograins using molecular dynamics with a reactive potential, namely ReaxFF. We found nonhydroxylated amorphous silica nanoparticles stick with higher probability than their hydroxylated counterpart. This difference is attributed to the preponderance of unsatisfied dangling bonds on the dry silicate surface which facilitate bond formation during collision, and thereby provide a mechanism for energy dissipation. The speed below which sticking occurs in the dry nanograins is much higher than that found in Earth-based experiments, which suggests any experimental study of dust grain collision should take into account of the chemical environment. We probe into the nanograin collisions further and carry out atomistic simulatons of collisions of molten silica nanograins. We observed in the molten state, amorphous silica is more sticky than it is in the solid phase. This happens due to increased viscoelastic energy dissipation. The result may explain how rocky planets originated from the inner rings of the protoplanetay disks where temperatures were as high as $\sim$ 2000 K. In order to increase the range of materials that could be simulated with ReaxFF potential, and also to examine the different oxidation states of iron associated with nanophase iron formation during space weathering, we made attempt to develop ReaxFF potential for fayalite (Fe$_2$SiO$_4$). We found out fundamental limitations of ReaxFF model to describe three-component minerals. However, during the fitting process we developed a model for iron silicide (FeSi), and made attempt to improve the silica model to obtain better elastic properties. We report here the fitting processes and the observed limitations of ReaxFF model.
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Date Issued: 2017
Identifier: CFE0006907, ucf:51691
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006907

asteroids (3)	+ -
asteroid (2)	+ -
composition (2)	+ -
exoplanets (2)	+ -
meteorites (2)	+ -

photometry (2)	+ -
regolith (2)	+ -
space weathering (2)	+ -
spectroscopy (2)	+ -
1627 (1)	+ -
AFM (1)	+ -
Adhesion (1)	+ -
Asteroid Composition (1)	+ -
Asteroid Organics (1)	+ -
Asteroid Surfaces (1)	+ -
Asteroid spectroscopy (1)	+ -
Asteroids (1)	+ -
Atomic Force Microscopy (1)	+ -
BART (1)	+ -
CDD pictures (1)	+ -
Cassini (1)	+ -
Cohesion (1)	+ -
Comets (1)	+ -
Density (1)	+ -
Gaffey (1)	+ -
Hydrated Minerals (1)	+ -
Ivar (1)	+ -
Magnetic Susceptibility (1)	+ -
Meteorites (1)	+ -
Mid-Infrared Spectroscopy (1)	+ -

Britt, Daniel (14)	+ -
University of Central Florida (14)	+ -
Fernandez, Yan (7)	+ -
Peale, Robert (3)	+ -
Schelling, Patrick (3)	+ -

Campins, Humberto (2)	+ -
Colwell, Joshua (2)	+ -
Kara, Abdelkader (2)	+ -
Blecic, Jasmina (1)	+ -
Coffey, Kevin (1)	+ -
Davis, Jimmy (1)	+ -
Denis, Jean-Marc (1)	+ -
Dove, Adrienne (1)	+ -
Emery, Joshua (1)	+ -
Fernandez, Yanga (1)	+ -
Fortney, Jonathan (1)	+ -
Hargrove, Kelsey (1)	+ -
Harrington, Joseph (1)	+ -
Harris, Alan (1)	+ -
Hedman, Mathew (1)	+ -
Hernandez, Florencio (1)	+ -
Howell, Ellen (1)	+ -
Jardine, Keanna (1)	+ -
Jerousek, Richard (1)	+ -
Jones, Jenna (1)	+ -
Kelley, Michael (1)	+ -
Kokoouline, Viatcheslav (1)	+ -
Landsman, Zoe (1)	+ -
Lust, Nathaniel (1)	+ -
Macke, Robert (1)	+ -

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