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Exploration of Near Earth Objects (1998) / Chapter Skim
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2 Status of Current Research Programs
Pages 8-15

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From page 8...
... With the widespread application of sensitive CCD detectors in the 1990s, telescopic measurements of physical or mineralogical characteristics are currently available for about 80 NEOs, where the most common data are measurements of spectral properties. Time series measurements of the brightness variations of NEOs produce light curves revealing rotation rates in the range of several hours to days, similar to known rotations for main-belt asteroids.
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From page 9...
... Given current NEO population estimates, a thorough survey could reveal a sufficient number of close Earth approaches to allow Arecibo to construct 1000-pixel images of about one object per month. Thus, radar offers tremendous potential for achieving detailed shape models for a large number of NEOs.
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From page 10...
... Although the most reliable mineralogical interpretations require measurements extending into the near infrared, measurements in the visible wavelengths allow preliminary characterization according to the taxonomic groups established for main-belt asteroids. Many near-Earth asteroids fall into taxonomic categories over the same range as asteroids in the inner main belt.
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From page 11...
... , and carbon dioxide (CON. Although the ice component is inferred from daughter products measured in cometary comae, the chemical composition of the dust has been directly measured through mass spectrometers on board the Giotto and VEGA spacecraft sent to comet Halley and interplanetary dust particles (IDPs)
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From page 12...
... Phaeton and the associated Geminid meteor stream suggests that this body may also have been a comet. Although it is generally thought that cometary materials are sampled as interplanetary dust particles but are not represented in the world' s meteorite collections, this view may reflect ignorance about the nature of the nonvolatile (rocky)
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From page 13...
... Idai7 (see Figure 2.3~. The Galileo mission provided the first observations of the populations of small impact craters on asteroids, evidence for the probable presence of large spell surfaces, qualitative information on the thickness and development of asteroidal regoliths, support for the idea of optical maturation of surface materials, hints of possible internal structure, and the discovery of a co-orbiting moonlet around Ida.
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From page 14...
... Presumably this age reflects the time of collisional disruption of the parent body of the Koronis asteroid family, of which Ida is a member. Both Ida and Gaspra are elongate irregular bodies that have been interpreted as individual collisional fragments formed by the catastrophic disruption of larger objects, although other interpretations have been offered.
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From page 15...
... Most ordinary chondntes have been metamorphosed, and detailed thermal models for their parent asteroids have been constructed based on decay of short-lived radionuclides.2i Chondnte cooling histones, determined from nickel diffusion profiles in metal grains, suggest that many bodies were disrupted by impacts and subsequently reaccreted into "rubble piles." 22 Earth-approaching S asteroids, possibly representing fragments of bodies heated to varying degrees, may be especially instructive for understanding asteroid thermal evolution and accretionary structure. Many carbonaceous chondntes have suffered aqueous alteration, and the source of the fluids that caused alteration in C-type asteroids was probably ice, originally accreted along with rocky material and later melted by decay of short-lived radionuclides, electromagnetic induction heating, or impacts.23 Information on the maturity of asteroid regoliths and the duration of their exposure has also been gained from studies of meteorite regolith breccias.
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Key Terms

  • chondrite parent
  • interplanetary dust
  • parent bodies
  • dust particles
  • planetary science

  • carbonaceous chondrites
  • spectral properties
  • ordinary chondrite
  • thermal evolution
  • ordinary chondrites

  • axis spin
  • suffered aqueous
  • hed meteorites
  • enstatite achondrite
  • thermal histories

  • cosmic abundances
  • asteroid belt
  • aqueous alteration
  • meteorite types
  • comet halley

  • asteroids exhibit
  • chemical composition
  • close approaches
  • parent asteroids
  • physical characteristics

  • ice component
  • carbonaceous chondrite
  • current limits
  • crater density
  • spin state


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