There is currently running water on the Martian surface, and we assume it was also present in the past. The Viking spacecraft observed channels and dry river beds on the Martian surface. Charged particles ripped off the surface of a neutron star spiral around its magnetic field lines. This acceleration causes them to radiate. The surface of a neutron star pulsates, throwing off waves of radiation.
Pulsars radiate just like main-sequence stars.
Pulsars do not radiate, because not even light can escape their strong gravity. Nitrogen and oxygen. Radioactive decay of elements in Io's core heat up the rock to molten temperatures. Io is very close to the Sun. Io was formed later than the other Galilean satellites, so it hasn't finished cooling yet.