  The composition of the surface of the Galilean icy moons has been debated
since the Galileo mission. Several chemistries have been proposed to explain
the composition of the non-icy component of the moon's surfaces, notably,
sulphuric acid hydrates and magnesium and sodium sulphates. More recently,
magnesium and sodium chlorides have been proposed to explain features observed
in ground-based observations. We have considered four salts (NaCl, Na2SO4,
MgSO4 and MgCl2) with various concentrations, to produce salty ice analogues.
Granular particles were produced by a flash-freezing procedure. Additionally,
compact slabs of salty ices were produced by a slow crystallisation of salty
liquid solution. These two methods mimic the end-members (plumes and slow ice
block formation) for producing hydrated salty ices on the surface of icy moons
such as Europa and Ganymede. We have monitored the near-infrared (NIR)
evolution of our salty ices during sublimation, revealing differences between
the granular particles and the slabs. The slabs formed a higher amount of
hydrates and the most highly hydrated compounds. Granular ices must be formed
from a more concentrated salty solution to increase the amount of hydrates
within the ice particles. The sublimation of salty ices removed all excess
water ice efficiently, but the dehydration of the salts was not observed. The
final spectra of the slabs were most flattened around 1.5 and 2.0 {\mu}m,
especially for the Na2SO4, MgCl2 and MgSO4, suggesting the presence of stable,
highly hydrated compounds. We find that Na2SO4, MgCl2 and MgSO4 are most
compatible with the non-icy component at the surface of the icy moons as
observed by the NIMS instrument on Galileo and by ground-based observations.
