Context :

Aims : To derive the thermal inertia of 2008 EV _ { 5 } , 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 are obtained by fitting an asteroid thermophysical model to NASA ’ s Wide-field Infrared Survey Explorer ( WISE ) infrared data .
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 ) , grain size is derived .

Results : We obtain an effective diameter D = 370 \pm 6 \mathrm { m } , geometric visible albedo p _ { V } = 0.13 \pm 0.05 ( assuming H = 20.0 \pm 0.4 ) , and thermal inertia \Gamma = 450 \pm 60 J m ^ { -2 } s ^ { -1 / 2 } K ^ { -1 } at the 1- \sigma 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 .

Conclusions :