Thermophysical properties of near-Earth asteroid (341843) 2008 EV5from WISE data

Aims. We derive the thermal inertia of 2008 EV5, the baseline target for the Marco Polo-R mission proposal, and infer information about the size of the particles on its surface. Methods. Values of thermal inertia were obtained by fitting an asteroid thermophysical model to NASA’s Wide-field Infrared Survey Explorer (WISE) infrared data. Grain size was derived from the constrained thermal inertia and a model of heat conductivity that accounts for different values of the packing fraction (a measure of the degree of compaction of the regolith particles). Results. We obtain an effective diameter D = 370 ± 6 m, geometric visible albedo pV = 0.13 ± 0.05 (assuming H = 20.0 ± 0.4), and thermal inertia Γ= 450 ± 60 J m −2 s −1/2 K −1 at the 1σ level of significance for its retrograde spin-pole solution. The regolith particles radius is r = 6.6 +1.3 −1.3 mm for low degrees of compaction and r = 12.5 +2.7 −2.6 mm for the highest packing densities.