Structural Origin of the Gravitino Mass Term: Geometric and Supergravity Perspectives

We identify a minimal superspace projector that uniquely selects the Rarita Schwinger mass bilinear in four-dimensional N=1 supergravity. Working in a reduced superspace with a single fermionic direction, we show that Berezin projection of a canonical even supergeometric form isolates the unique Lorentz-invariant fermionic bilinear compatible with local supersymmetry. The construction is predynamical: it fixes the algebraic structure of the gravitino mass term independently of supersymmetry breaking mechanisms, background geometry, or matter couplings. We show that this projector embeds consistently into curved superspace, extends to N>1 theories, and clarifies the universality of the gravitino mass structure in supergravity.