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Title: THE UV/BLUE EFFECTS OF SPACE WEATHERING MANIFESTED IN S-COMPLEX ASTEROIDS. I. QUANTIFYING CHANGE WITH ASTEROID AGE

Evidence for the manifestation of space weathering in S-complex asteroids as a bluing of the UV/blue reflectance spectrum is extended using high resolution CCD reflectance spectra of 21 main-belt, 1 Mars-crossing, and 3 near-Earth asteroids covering a wavelength range of 320–620 nm. Demonstration of the transition of iron-bearing materials from volume scattering to surface (Fresnel) scattering is apparent as an abrupt downturn at wavelengths just short of 400 nm in reflectance spectra of fresh asteroid surfaces. The weathering away of this downturn is demonstrated by its absence in reflectance spectra of mature S-complex asteroids, consistent with an increase in npFe{sup 0} on the material's surface. Modeling of the effects of the addition of small amounts of npFe{sup 0} to particles from both a hypothetical mineral and a terrestrial basalt shows that evidence of the addition of 0.0001% npFe{sup 0} affects the reflectance at UV/blue wavelengths, while the addition of 0.01% is required to see the visible/near-infrared reddening and diminution of absorption features. Thus, the UV/blue reflectance characteristics allow earlier detection of the onset of space weathering effects. Combining UV/blue spectral characteristics of asteroids and ordinary chondrite meteorites with estimated ages of the young Datura family, we establish a method ofmore » dating asteroid surface ages during the early stages of space weathering. We demonstrate by dating the surface of NEA 163249 2002 GT to be 109 (±18) to 128 (±10) Kyr.« less
Authors:
 [1] ;  [2]
  1. MMT Observatory, Tucson, AZ (United States)
  2. Planetary Science Institute, 1700 E. Fort Lowell Rd., Suite 106, Tucson, AZ 85719 (United States)
Publication Date:
OSTI Identifier:
22520172
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 150; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AGE ESTIMATION; ASTEROIDS; BASALT; CHARGE-COUPLED DEVICES; CHONDRITES; EMISSION SPECTRA; EMISSION SPECTROSCOPY; IRON; MARS PLANET; NANOPARTICLES; SATELLITES; SPECTRAL REFLECTANCE; SURFACES; ULTRAVIOLET RADIATION; WEATHERING