Evidence of surface heterogeneity on active asteroid (3200) Phaethon

Thermal infrared emission and thermophysical modeling techniques are powerful tools in deciphering the surface properties of asteroids. The near-Earth asteroid (3200) Phaethon is an active with a very small perihelion distance likely source Geminid meteor shower. We estimate interpret thermal inertia this extraordinary using observations that span ten distinct sightings. variation over these sightings inconsistent expected temperature-dependent theorized from radiative heat transfer within regolith. Thus, we test whether can be explained by regolith layer bedrock two spatially heterogeneous scenarios. find model which Phaethon's north south hemispheres have distinctly different sufficiently explain thermal-inertias determined herein. In particular, boundary located between latitudes -30 deg +10 separates fine-grained southern northern hemisphere dominated coarse-grained and/or high coverage porous boulders. discuss implications related to activity potential association 2005 UD.