  A search for water masers in 47 Sloan Digital Sky Survey Type 2 quasars using
the Green Bank Telescope has yielded a detection at a redshift of z = 0.660.
This maser is more than an order of magnitude higher in redshift than any
previously known and, with a total isotropic luminosity of 23,000 L_sun, also
the most powerful. The presence and detectability of water masers in quasars at
z ~ 0.3-0.8 may provide a better understanding of quasar molecular tori and
disks, as well as fundamental quasar and galaxy properties such as black hole
masses. Water masers at cosmologically interesting distances may also
eventually provide, via direct distance determinations, a new cosmological
observable for testing the reality and properties of dark energy, currently
inferred primarily through Type 1a supernova measurements.
