Search

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'sWide-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 ± 6m, 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 = 12.5-2.6+2.7 mm for the highest packing densities. [ABSTRACT FROM AUTHOR]