You are here

Spectral Study of Asteroids and Laboratory Simulated Asteroid Organics

Download pdf | Full Screen View

Date Issued:
2015
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 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.
Title: Spectral Study of Asteroids and Laboratory Simulated Asteroid Organics.
0 views
0 downloads
Name(s): Hargrove, Kelsey, Author
Colwell, Joshua, Committee Chair
Fernandez, Yan, Committee Member
Britt, Daniel, Committee Member
Kelley, Michael, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2015
Publisher: University of Central Florida
Language(s): English
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 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.
Identifier: CFE0005624 (IID), ucf:50201 (fedora)
Note(s): 2015-05-01
Ph.D.
Sciences, Physics
Doctoral
This record was generated from author submitted information.
Subject(s): Asteroids -- Asteroid spectroscopy -- Asteroid Composition -- Near-Infrared Spectroscopy -- Mid-Infrared Spectroscopy -- Asteroid Organics -- Hydrated Minerals -- Silicates -- Primitive Asteroids
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0005624
Restrictions on Access: campus 2016-05-15
Host Institution: UCF

In Collections