<P> Through the 1970s , it was widely believed that neutrinos were massless and their flavors were invariant . However , in 1968 Pontecorvo proposed that if neutrinos had mass , then they could change from one flavor to another . Thus , the `` missing '' solar neutrinos could be electron neutrinos which changed into other flavors along the way to Earth , rendering them invisible to the detectors in the Homestake Mine and contemporary neutrino observatories . </P>
the solution of the missing neutrino problem from the sun 's core was resolved by the discovery of
neutrinos had mass