  We find that if solid xenon is formed from liquid xenon, denoted "ice", there
is a 10% increase of $^{129}$Xe longitudinal relaxation $T_1$ time (taken at 77
K and 2 Tesla) over a trickle-freeze formation, denoted "snow". Forming xenon
ice also gives unprecedented reproducibility of $^{129}$Xe $T_1$ measurements
across a range of 77-150 K. This temperature dependence roughly follows the
theory of spin-rotation mediated by Raman scattering of harmonic phonons
(SRRS), though it results in a smaller-than-predicted spin-rotation coupling
strength $c_{K0}/h$. Enriched ice $^{129}$Xe $T_1$ experiments show no isotopic
dependence in bulk relaxation mechanisms at 77 K and at kilogauss fields.
