  We consider the possibility that the particles in the Ultra High Energy
Cosmic Rays arriving to Earth might be neutrons instead of protons. We stress
that in such case the argument for the GZK cutoff is weaker and that it is
conceivable that neutrons would not be affected by it. This scenario would
require the neutron to start with an energy larger than the observed one, in
order to be able to travel the distances involved, within its proper life-time.
It must then loose most of the extra energy through interaction with the
galactic dark matter or some other matter in the intergalactic medium.
