A new material for the icy Galilean moons: The structure of sulfuric acid hexahydrate

Abstract

[1] This study presents a newly identified water-rich crystalline form of sulfuric acid hydrate, H 2 SO 4 •6H 2 O, a hexahydrate. The method of formation of this material suggests that sulfuric acid hexahydrate (SAHx) could be an abundant material on the surface of Jupiter's Galilean ice moons, Europa, Ganymede, and Callisto. The structure of SAHx was determined by the combined use of synchrotron X-ray and neutron powder diffraction data. The structural arrangement of SAHx exhibits the same water layer topology that has been determined for sulfuric acid octahydrate (SAO), but differs in the stacking of this water layer and the interlayer species. SAHx is observed to form over a large range of solution compositions and displays stability over the temperature range 80 to 190 K.Citation: Maynard-Casely, H. E., K. S. Wallwork, and M. Avdeev (2013), A new material for the icy Galilean moons: The structure of sulfuric acid hexahydrate,

Mineral Diversity on Europa: Exploration of Phases Formed in the MgSO4–H2SO4–H2O Ternary

“…35 This is particularly important for hydrate systems where laboratory reference spectra that are currently being used to interpret observation data may be multiphase. Such issues have been seen previously; the hydrate sulfuric acid hexahydrate 13 was not discovered until 2013, and its presence could explain the disparity in previous studies of sulfuric acid octahydrate. 36 This work further highlights the need of laboratory studies to understand other ternary and mixtures, 10 identify novel hydrates, and seek to categorize their near-IR…”

“…Since publication of that review, there have been a number of developments in the understanding of these hydrate materials. First, in the understanding of the sulfuric acid hydrates, the structure of sulfuric acid octahydrate (H 2 SO 4 ·8H 2 O) has been clarified, and a new hydrate (sulfuric acid hexahydrate (H 2 SO 4 ·6H 2 O)) has been identified . Second, a new magnesium sulfate hydrate has been discovered, a nonohydrate (MgSO 4 ·9H 2 O), and identified within an evaporite lake on Earth.…”

“…First, in the understanding of the sulfuric acid hydrates, the structure of sulfuric acid octahydrate (H 2 SO 4 •8H 2 O) has been clarified, 12 and a new hydrate (sulfuric acid hexahydrate (H 2 SO 4 •6H 2 O)) has been identified. 13 Second, a new magnesium sulfate hydrate has been discovered, a nonohydrate (MgSO 4 •9H 2 O), 14 and identified within an evaporite lake on Earth. Given this large structure variability and the fact the new phases are still being identified, it seems highly likely that any interaction between exogenic (in this case sulfuric acid hydrates) and endogenic (magnesium sulfate hydrates) upon Europa will result in yet more mineral diversity.…”

Standoff Raman spectroscopy for future Europa Lander missions

“…The newly discovered SAHx is orthorhombic, space group P2 1 2 1 2 1 with Z = 4. [55] The structure of SAHx consists of D 3 O + and D 2 O layers, [56,57] which sandwich a layer of D 5 [61] The Raman line at 981 cm −1 originates from the ν 1 (A 1 ), a nondegenerate symmetric stretching of oxygen atoms of SO 4 . The doubly (E) and triply (T) degenerate vibrational modes of SO 4 ions corresponding to the symmetric bending, ν 2 (E), antisymmetric stretch, ν 3 (T 2 ), and antisymmetric bending, ν 4 (T 2 ), modes appear at 450, 1,105, and 614 cm −1 , respectively.…”

What you see and what you get: combining near-infrared spectroscopy with powder diffraction

“…This is made more challenging for application of this technique to icy moon surfaces as knowledge of the mineralogical behaviours of materials comprising these ices is lacking. Indeed, new hydrates that could exist on these bodies are still being discovered (Maynard-Casely et al ., 2013; Fortes et al ., 2017).…”