Recent works have shown that the thermal inertia of km-sized near-Earth asteroids ( NEAs ) is more than two orders of magnitude higher than that of main belt asteroids ( MBAs ) with sizes ( diameters ) between 200 and 1,000 km .
This confirms the idea that large MBAs , over hundreds millions of years , have developed a fine and thick thermally insulating regolith layer , responsible for the low values of their thermal inertia , whereas km-sized asteroids , having collisional lifetimes of only some millions years , have less regolith , and consequently a larger surface thermal inertia .

Because it is believed that regolith on asteroids forms as a result of impact processes , a better knowledge of asteroid thermal inertia and its correlation with size , taxonomic type , and density can be used as an important constraint for modeling of impact processes on asteroids .
However , our knowledge of asteroids ’ thermal inertia values is still based on few data points with NEAs covering the size range 0.1–20 km and MBAs that > 100 km .

Here , we use IRAS infrared measurements to estimate the thermal inertia values of MBAs with diameters < 100 km and known shapes and spin vector : filling an important size gap between the largest MBAs and the km-sized NEAs .
An update to the inverse correlation between thermal inertia and diameter is presented .
For some asteroids thermophysical modelling allowed us to discriminate between the two still possible spin vector solutions derived from optical lightcurve inversion .
This is important for ( 720 ) Bohlinia : our preferred solution was predicted to be the correct one by Vokrouhlický et al .
( 2003 , Nature 425 , 147 ) just on theoretical grounds .