  The thermal inertia of an asteroid's surface can provide insight into
regolith properties, such as the presence of a layer of fine dust, the density
and thermal conductivity of a rocky surface, and, together with other
observational data, mineralogy. Knowledge of the surface characteristics of
asteroids is important for planetary defense initiatives and the extraction of
resources ("asteroid mining"). A simple means of estimating asteroid thermal
inertia has been proposed by Harris & Drube, which is suitable for application
to large sets of thermal-infrared observational data, such as those obtained by
infrared space telescopes. We compare results from the Harris-Drube estimator
with recently published values of asteroid thermal inertia from detailed
thermophysical modeling, and provide an explanation in terms of reduced surface
roughness for some discrepant results. Smooth surfaces covered in fine dust may
provide an explanation for the unexpectedly low values of thermal inertia
derived from thermophysical modeling for some slowly rotating main-belt
asteroids (MBAs). In the case of near-Earth objects (NEOs) we show that results
from the estimator are in good agreement with those from thermophysical
modeling, with just a few exceptions. We discuss the special cases of the NEOs
(101955) Bennu, (162173) Ryugu, and (29075) 1950 DA in the context of results
from our estimator. Given the data requirements and complexity of
thermophysical modeling, data-analysis tools based on relatively simple
concepts can play an important role in allowing "quick-look" assessment of
thermal-infrared data of asteroids, especially NEOs.
