We identified betaine as the main compatible solute accumulated by Bacillus pumilus, Cobetia marina, and Salinibacter ruber when exposed to salinity conditions similar to those of the liquid water ocean of Europa. Quantitative nuclear magnetic resonance spectra helped in the compatible solute characterization while different concentrations of NaCl, Na2SO4, and MgSO4 were used to simulate the salinity of Europa’s ocean.