Shape and solar phase angle effects on the taxonomic classification of asteroids

Abstract:

Asteroid taxonomy groups asteroids into classes based on
similarities of their observational properties, of which the most
commonly used are measurments of spectral reflectance in the
visible and geometric albedo. It is a commonly used proxy for
asteroid composition, since it can be derived from observations
that are available for a large number of objects. However, the
correspondence between asteroid taxonomy and asteroid composition
is not univocal, for two main reasons: 1) not all compositions
produce spectra with diagnostic features in the range used to
derive the taxonomy; and 2) both the spectra and albedos of
asteroids are also affected by other factors that are not
directly related to composition. The main effect of the first
reason is that asteroids with very different compositions may end
up in a same taxonomic class, while the second reason may produce
situations where asteroids of a given composition are
classified into several different taxonomic groups. The physical
causes for this later effect include the properties of the
top regolith layer that cover the asteroid surface ( grain size
distribution, porosity and rugosity) and processes that operate in
this layer (space wethering by solar wind implatation and
micro-meteorite bombardment). These are intrinsic properties
of each body. Other causes however are linked to the particular
geometry at the time of the observations, like solar phase angle,
aspect angle and shape.

In this work I review how solar phase angle and shape effects may
affect the taxonomic classification of asteroids.