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Author: Ronald Adrey Fevig
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
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Book Description
Results of visible to near-infrared spectrophotometric observations of 55 near-Earth asteroids (NEAs) are reported. The observing techniques, instrumentation, and method of data analysis are described. A new asteroid classification method that directly compares these NEA spectra with spectral features of meteorites is presented. Two major siliceous groups (having discernible"1-micron"absorptions) result from this method, OC-likes which match the spectra of ordinary chondrites and S-types. The dataset shows a preponderance of spectra consistent with ordinary chondrites (23 NEAs), as well as S-types (19), 2 with spectra consistent with black ordinary chondrites, 2 R-types, and 9 that show no 1-micron absorption. The spectral characteristics of the siliceous S-type and OC-like asteroids blend together, providing evidence that S-type asteroids are simply ordinary chondrites whose surface has been modified by weathering. This helps resolve the long standing question of the lack of main belt asteroids having spectra matching ordinary chondrite meteorites. Main belt asteroids have on average much older surfaces while NEAs that exhibit OC-like spectra have younger surfaces. It was found that fresh objects having spectra consistent with ordinary chondrites (1) occupy mostly highly eccentric Apollo orbits which encounter a strong collisional environment in the asteroid main-belt, (2) may have been recently injected into high eccentricity orbits, or (3) have suffered tidal disruption. S-type NEAs reside primarily in orbits that do not cross the asteroid main-belt. This orbit dependent trend is verified by using the larger NEA dataset of Binzel et al. (2004a). Nine NEAs from this survey exhibiting no 1-micron absorption can be associated with extinct comets, iron meteorites or enstatite meteorites. It is shown that most of these NEAs must be extinct comets, implying a considerably larger fraction of comets among the NEA population than previously thought. A correlation of these objects with low inclination orbits is found. This study finds that the NEA population is divided roughly as follows: 4̃0% fresh ordinary chondrites, 3̃5% S-types, 2̃0% extinct comet candidates, and 5̃% in minor classes. This work may guide NEA mitigation planning should such an emergency arise.
Author: Ronald Adrey Fevig
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
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Book Description
Results of visible to near-infrared spectrophotometric observations of 55 near-Earth asteroids (NEAs) are reported. The observing techniques, instrumentation, and method of data analysis are described. A new asteroid classification method that directly compares these NEA spectra with spectral features of meteorites is presented. Two major siliceous groups (having discernible"1-micron"absorptions) result from this method, OC-likes which match the spectra of ordinary chondrites and S-types. The dataset shows a preponderance of spectra consistent with ordinary chondrites (23 NEAs), as well as S-types (19), 2 with spectra consistent with black ordinary chondrites, 2 R-types, and 9 that show no 1-micron absorption. The spectral characteristics of the siliceous S-type and OC-like asteroids blend together, providing evidence that S-type asteroids are simply ordinary chondrites whose surface has been modified by weathering. This helps resolve the long standing question of the lack of main belt asteroids having spectra matching ordinary chondrite meteorites. Main belt asteroids have on average much older surfaces while NEAs that exhibit OC-like spectra have younger surfaces. It was found that fresh objects having spectra consistent with ordinary chondrites (1) occupy mostly highly eccentric Apollo orbits which encounter a strong collisional environment in the asteroid main-belt, (2) may have been recently injected into high eccentricity orbits, or (3) have suffered tidal disruption. S-type NEAs reside primarily in orbits that do not cross the asteroid main-belt. This orbit dependent trend is verified by using the larger NEA dataset of Binzel et al. (2004a). Nine NEAs from this survey exhibiting no 1-micron absorption can be associated with extinct comets, iron meteorites or enstatite meteorites. It is shown that most of these NEAs must be extinct comets, implying a considerably larger fraction of comets among the NEA population than previously thought. A correlation of these objects with low inclination orbits is found. This study finds that the NEA population is divided roughly as follows: 4̃0% fresh ordinary chondrites, 3̃5% S-types, 2̃0% extinct comet candidates, and 5̃% in minor classes. This work may guide NEA mitigation planning should such an emergency arise.
Author: Anicia Arredondo
Publisher:
ISBN:
Category :
Languages : en
Pages : 204
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Book Description
Primitive asteroids have remained mostly unprocessed since their formation, and the study of these populations has implications about the conditions of the early solar system and the evolution of the asteroid belt. This spectroscopic study of inner main-belt (IMB) primitive asteroids addresses three central objectives: 1) determine the origin and composition of objects in the near-Earth object population, particularly spacecraft targets; 2) test theories of how processes such as space weathering and aqueous alteration affect surface properties of small, low-albedo bodies; and 3) explore how primitive objects in the background population (i.e., asteroids not belonging to dynamical families) relate to each other and their implications for the evolution of the asteroid belt. In this work, I use the NASA Infrared Telescope Facility and the Telescopio Nazionale Galileo to obtain near-infrared (NIR; 0.7 to 2.5 microns) spectra of objects from three families and the background population. I compare the sample spectra with the published spectra of near-Earth objects and dynamical studies to test arguments for origin. I compare the VNIR spectra with laboratory spectra of meteorites to constrain the asteroid compositions. I test for space-weathering effects by comparing the spectra of the younger families with the older, more-weathered families. I look for trends between the spectra of objects in the background family and their physical and orbital properties to uncover information about this primordial population at the time of formation and throughout its evolution. Chapter 3 describes the NIR characterization of the Klio family. Chapter 4 describes the NIR characterization of the Chaldaea family and its relationship to the Klio family. In Chapter 5, I characterize the Sulamitis family and compare with the Polana family. Finally, in Chapter 6 I characterize the primitive background population and compare the background objects with the families at similar locations.
Author: Michael W. Busch
Publisher: Universal-Publishers
ISBN: 1599423227
Category : Science
Languages : en
Pages : 126
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Book Description
Asteroids are diverse and numerous solar system objects, from the large number of objects in the main asteroid belt to the relatively small near-Earth population. Understanding their physical properties is essential to understanding the evolution of the solar system, and asteroid morphology is a complex field in its own right. The histories of individual asteroids, and particularly near-Earth objects, reflect continuous interaction among their shapes, rotation states, and orbits due to the effects of radiation pressure. Radar astronomy has provided detailed information on the orbits, sizes, shapes, rotation states, and composition of many asteroids. To improve the capabilities of asteroid radar observations, I have developed the technique of radar speckle tracking. The echoes from different points on the surface of a radar target interfere with each other, producing a pattern of bright and dark speckles across the surface of the Earth. Using radio astronomy techniques, I track the motion of speckles between several ground stations during a radar experiment to accurately determine the rotation state of the target. Speckle tracking is a powerful tool both to determine the orbital evolution of near-Earth asteroids, particularly potential Earth impactors, and to survey the overall physical properties of the asteroid population. In addition, I have studied applying the techniques of adaptive optics and radio interferometry to asteroid science. These will become more useful with the next generation of asteroid-detecting surveys and the construction of large sub-millimeter interferometers. Interferometry in particular will soon be able to survey the entire asteroid belt.
Author: International Astronomical Union. Symposium
Publisher: Cambridge University Press
ISBN: 9780521863452
Category : Science
Languages : en
Pages : 538
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Book Description
IAU S236 concentrates on specific techniques of observation and modeling Near Earth Objects (NEOs).
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309493986
Category : Science
Languages : en
Pages : 75
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Book Description
Near Earth objects (NEOs) have the potential to cause significant damage on Earth. In December 2018, an asteroid exploded in the upper atmosphere over the Bering Sea (western Pacific Ocean) with the explosive force of nearly 10 times that of the Hiroshima bomb. While the frequency of NEO impacts rises in inverse proportion to their sizes, it is still critical to monitor NEO activity in order to prepare defenses for these rare but dangerous threats. Currently, NASA funds a network of ground-based telescopes and a single, soon-to-expire space-based asset to detect and track large asteroids that could cause major damage if they struck Earth. This asset is crucial to NEO tracking as thermal-infrared detection and tracking of asteroids can only be accomplished on a space-based platform. Finding Hazardous Asteroids Using Infrared and Visible Wavelength Telescopes explores the advantages and disadvantages of infrared (IR) technology and visible wavelength observations of NEOs. This report reviews the techniques that could be used to obtain NEO sizes from an infrared spectrum and delineate the associated errors in determining the size. It also evaluates the strengths and weaknesses of these techniques and recommends the most valid techniques that give reproducible results with quantifiable errors.
Author: International Astronomical Union. Symposium
Publisher: Cambridge University Press
ISBN: 9780521852005
Category : Science
Languages : en
Pages : 488
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Book Description
Proceedings of IAU Symposium 229 on minor bodies of the solar system, for researchers and graduate students of planetary sciences.
Author: Patrick Michel
Publisher: University of Arizona Press
ISBN: 0816532133
Category : Science
Languages : en
Pages : 946
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Book Description
"More than forty chapters detail our current astronomical, compositional, geological, and geophysical knowledge of asteroids, as well as their unique physical processes and interrelationships with comets and meteorites"--Provided by publisher.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 902
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Book Description
Author: Patrick Michel
Publisher: University of Arizona Press
ISBN: 0816532184
Category : Science
Languages : en
Pages : 946
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Book Description
Over the past decade, asteroids have come to the forefront of planetary science. Scientists across broad disciplines are increasingly recognizing that understanding asteroids is essential to discerning the basic processes of planetary formation, including how their current distribution bespeaks our solar system’s cataclysmic past. For explorers, the nearest asteroids beckon as the most accessible milestones in interplanetary space, offering spaceflight destinations easier to reach than the lunar surface. For futurists, the prospects of asteroids as commercial resources tantalize as a twenty-first-century gold rush, albeit with far greater challenges than faced by nineteenth-century pioneers. For humanity, it is the realization that asteroids matter. It is not a question of if—but when—the next major impact will occur. While the disaster probabilities are thankfully small, fully cataloging and characterizing the potentially hazardous asteroid population remains unfinished business. Asteroids IV sets the latest scientific foundation upon which all these topics and more will be built upon for the future. Nearly 150 international authorities through more than 40 chapters convey the definitive state of the field by detailing our current astronomical, compositional, geological, and geophysical knowledge of asteroids, as well as their unique physical processes and interrelationships with comets and meteorites. Most importantly, this volume outlines the outstanding questions that will focus and drive researchers and students of all ages toward new advances in the coming decade and beyond.
Author: Leon Sinclair
Publisher: Nova Science Publishers
ISBN: 9781634840675
Category : Asteroids
Languages : en
Pages : 0
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Book Description
Scientists classify comets and asteroids that pass within 28 million miles of Earth's orbit as near-Earth objects (NEOs). Asteroids that collide and break into smaller fragments are the source of most NEOs, and the resulting fragments bombard the Earth at the rate of over 100 tons a day. Although the vast majority of NEOs that enter Earth's atmosphere disintegrate before reaching the surface, those larger than 100 meters (328 feet) may survive the descent and cause destruction in and around their impact sites. Furthermore, even smaller objects that disintegrate before reaching Earth's surface can cause significant damage. This book examines NASA's NEO Program and assesses the Agency's progress toward meeting statutory and other Program goals. Specifically, it reviews NASA's allocation and use of resources and plans for the future of the Program.
