  The evolution of the ground-state nuclear shapes in neutron-rich Sr, Zr, and
Mo isotopes, including both even-even and odd-A nuclei, is studied within a
self-consistent mean-field approximation based on the D1S Gogny interaction.
Neutron separation energies and charge radii are calculated and compared with
available data. A correlation between a shape transition and a discontinuity in
those observables is found microscopically. While in Sr and Zr isotopes the
steep behavior observed in the isotopic dependence of the charge radii is a
consequence of a sharp prolate-oblate transition, the smooth behavior found in
Mo isotopes has its origin in an emergent region of triaxiality.
