Evidence for an ocean beneath the icy crust of Europa includes reflectance spectra of disrupted surface regions indicating hydrated materials such as salts. We simulated exposure of salty brine on the cold surface of Europa by flash-freezing sulfate and carbonate solutions. This produces materials that have near-infrared reflectance spectra distinct from those for crystalline minerals and more similar to those for Europa's non-ice regions. These new spectroscopic data, along with geophysical evidence, geochemical models, and meteorite studies, strongly suggest that the non-ice materials in the disrupted regions on Europa's surface contain large amounts of disordered and heavily hydrated MgSO4 and perhaps Na2SO4 that are endogenic in origin.