  Depolarizing collisions are elastic or quasielastic collisions that equalize
the populations and destroy the coherence between the magnetic sublevels of
atomic levels. In astrophysical plasmas, the main depolarizing collider is
neutral hydrogen. We consider depolarizing rates on the lowest levels of
neutral and singly ionized alkaly-earths Mg I, Sr I, Ba I, Mg II, Ca II, and Ba
II, due to collisions with H. We compute ab initio potential curves of the
atom-H system and solve the quantum mechanical dynamics. From the scattering
amplitudes we calculate the depolarizing rates for Maxwellian distributions of
colliders at temperatures T <10000 K. A comparative analysis of our results and
previous calculations in the literature is done. We discuss the effect of these
rates on the formation of scattering polarization patterns of resonant lines of
alkali-earths in the solar atmosphere, and their effect on Hanle effect
diagnostics of solar magnetic fields.
