  Realistic superstring models generically give rise to exotic matter states,
which arise due to the ``Wilson-line'' breaking of the non-Abelian unifying
gauge symmetry. Often such states are protected by a gauge or local discrete
symmetry and therefore may be stable or meta-stable. We study the possibility
of a flux of high energy neutrinos coming from the sun and the earth due to the
annihilation of such exotic string states. We also discuss the expected flux
for other heavy stable particles -- like the gluino LSP. We comment that the
detection of ultra-energetic neutrinos from the sun and the earth imposes model
independent constraints on the high energy cutoff, as for example in the
recently entertained TeV scale Kaluza-Klein theories. We therefore propose that
improved experimental resolution of the energy of the muons in neutrino
detectors together with their correlation with neutrinos from the sun and the
center of the earth will serve as a probe of the desert in Gravity Unified
Theories.
