Supersingular elliptic surfaces and Infinitesimal Torelli

In 1981 Katsura presented a classification of non-rational Jacobian elliptic surfaces which admit a base change which is rational. In 2004 we presented a classification of Jacobian regular elliptic surfaces which do not satisfy infinitesimal Torelli. These classifications of quite different properties turn out to be very similar. In this paper we use an argument exploiting the product-quotient structure of these examples to prove simultaneously that Katsura’s examples are Artin supersingular, and to give a new proof that our examples do not satisfy infinitesimal Torelli.