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Abstract

Mountains or non-axisymmetric deformations of rotating neutron stars (NS)
efficiently radiate gravitational waves (GW). We consider analogies between NS
mountains and surface features of solar system bodies. Both NS and moons such
as Europa or Enceladus have thin crusts over deep oceans while Mercury has a
thin crust over a large metallic core. Thin sheets may wrinkle in universal
ways. Europa has linear features, Enceladus has ``Tiger" stripes, and Mercury
has lobate scarps. NS may have analogous features. The innermost inner core of
the Earth is anisotropic with a shear modulus that depends on direction. If NS
crust material is also anisotropic this will produce an ellipticity, when the
crust is stressed, that grows with spin frequency. This yields a breaking index
(log derivative of spin down rate) very different from $n=5$ and could explain
the maximum spin observed for neutron stars and a possible minimum ellipticity
of millisecond pulsars.