Galilean Satellites of Jupiter Exhibit Polarization Opposition Effect

M. I. Mishchenko (NASA GISS), V. K. Rosenbush, V. V. Avramchuk, A. E. Rosenbush (Main Astronomical Observatory, Kiev)

We present new detailed polarimetric measurements of the Galilean satellites of Jupiter with U, B, V, and R filters at phase angles ranging from 12 to nearly 0 degrees. The polarization phase curves of Io, Europa, and Ganymede in the B, V, and R filters clearly show the presence of the polarization opposition effect in the form of a sharp peak of negative polarization centered at a very small phase angle of 0.6-0.7 degrees and superimposed on the regular negative polarization branch. This phase angle is comparable to the width of the spike-like photometric opposition effect observed for Europa. Theoretical computations based on the theory of weak photon localization indicate that both opposition phenomena are likely to be produced by the coherent backscattering mechanism.