The population of small near-Earth objects: composition, source regions and rotational properties
The Planetary Science Journal(2024)
摘要
The study of small (<300 m) near-Earth objects (NEOs) is important because
they are more closely related than larger objects to the precursors of
meteorites that fall on Earth. Collisions of these bodies with Earth are also
more frequent. Although such collisions cannot produce massive extinction
events, they can still produce significant local damage. Here we present the
results of a photometric and spectroscopic survey of small NEOs, which include
near-infrared (NIR) spectra of 84 objects with a mean diameter of 126 m and
photometric data of 59 objects with a mean diameter of 87 m. We found that
S-complex asteroids are the most abundant among the NEOs, comprising ∼66%
of the sample. Most asteroids in the S-complex were found to have compositions
consistent with LL-chondrites. Our study revealed the existence of NEOs with
spectral characteristics similar to those in the S-complex, but that could be
hidden within the C- or X-complex due to their weak absorption bands. We
suggest that the presence of metal or shock-darkening could be responsible for
the attenuation of the absorption bands. These objects have been grouped into a
new subclass within the S-complex called Sx-types. The dynamical modeling
showed that 83% of the NEOs escaped from the ν_6 resonance, 16% from
the 3:1 and just 1% from the 5:2 resonance. Lightcurves and rotational periods
were derived from the photometric data. No clear trend between the axis ratio
and the absolute magnitude or rotational period of the NEOs was found.
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关键词
Asteroids,Near-Earth objects,Spectroscopy,Photometry
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