  Sulfur is the tenth most abundant element in the universe and is known to
play a significant role in biological systems. Accordingly, in recent years
there has been increased interest in the role of sulfur in astrochemical
reactions and planetary geology and geochemistry. Among the many avenues of
research currently being explored is the laboratory processing of astrophysical
ice analogues. Such research involves the synthesis of an ice of specific
morphology and chemical composition at temperatures and pressures relevant to a
selected astrophysical setting (such as the interstellar medium or the surfaces
of icy moons). Subsequent processing of the ice under conditions that simulate
the selected astrophysical setting commonly involves radiolysis, photolysis,
thermal processing, neutral-neutral fragment chemistry, or any combination of
these, and has been the subject of several studies. The in-situ changes in ice
morphology and chemistry occurring during such processing has been monitored
via spectroscopic or spectrometric techniques. In this paper, we have reviewed
the results of laboratory investigations concerned with sulfur chemistry in
several astrophysical ice analogues. Specifically, we review (i) the
spectroscopy of sulfur-containing astrochemical molecules in the condensed
phase, (ii) atom and radical addition reactions, (iii) the thermal processing
of sulfur-bearing ices, (iv) photochemical experiments, (v) the non-reactive
charged particle radiolysis of sulfur-bearing ices, and (vi) sulfur ion
bombardment of and implantation in ice analogues. Potential future studies in
the field of solid phase sulfur astrochemistry are also discussed in the
context of forthcoming space missions, such as the NASA James Webb Space
Telescope and the ESA Jupiter Icy Moons Explorer mission.
