Supersingular K3 Surfaces are Unirational

Abstract: We show that supersingular K3 surfaces in characteristic $p\geq5$ are related sequences of very special correspondences. This is not enough to conclude that they are unirational. As a byproduct, we exhibit a fibration structure on the moduli space of rigidified K3 crystals. We also establish Shioda-Inose type isogeny theorems for K3 surfaces with Picard rank $\rho\geq19$ in positive characteristic.