TY - JOUR

T1 - Crystallography relevant to Mars and Galilean icy moons: Crystal behavior of kieserite-type monohydrate sulfates at extraterrestrial conditions down to 15 K

AU - Wildner, Manfred

AU - Zakharov, Boris A.

AU - Bogdanov, Nikita E.

AU - Talla, Dominik

AU - Boldyreva, Elena V.

AU - Miletich, Ronald

N1 - Funding Information: This work was supported by a grant from the Austrian Science Fund (FWF) (grant No. P 29149-N29), and the Russian Ministry of Science and Higher Education (grant No. AAAAA21- 121011390011-4 awarded to EVB, ZBA and NEB). Publisher Copyright: © 2022 International Union of Crystallography. All rights reserved.

PY - 2022/3/1

Y1 - 2022/3/1

N2 - Monohydrate sulfate kieserites (M2+SO4·H2O) and their solid solutions are essential constituents on the surface of Mars and most likely also on Galilean icy moons in our solar system. Phase stabilities of end-member representatives (M2+= Mg, Fe, Co, Ni) have been examined crystallographically using single-crystal X-ray diffraction at 1 bar and temperatures down to 15 K, by means of applying open He cryojet techniques at in-house laboratory instrumentation. All four representative phases show a comparable, highly anisotropic thermal expansion behavior with a remarkable negative thermal expansion along the monoclinic b axis and a pronounced anisotropic expansion perpendicular to it. The lattice changes down to 15 K correspond to an 'inverse thermal pressure' of approximately 0.7 GPa, which is far below the critical pressures of transition under hydrostatic compression (Pc≥ 2.40 GPa). Consequently, no equivalent structural phase transition was observed for any compound, and neither dehydration nor rearrangements of the hydrogen bonding schemes have been observed. The M2+SO4·H2O (M2+= Mg, Fe, Co, Ni) end-member phases preserve the kieserite-type C2/c symmetry; hydrogen bonds and other structural details were found to vary smoothly down to the lowest experimental temperature. These findings serve as an important basis for the assignment of sulfate-related signals in remote-sensing data obtained from orbiters at celestial bodies, as well as for thermodynamic considerations and modeling of properties of kieserite-type sulfate monohydrates relevant to extraterrestrial sulfate associations at very low temperatures.

AB - Monohydrate sulfate kieserites (M2+SO4·H2O) and their solid solutions are essential constituents on the surface of Mars and most likely also on Galilean icy moons in our solar system. Phase stabilities of end-member representatives (M2+= Mg, Fe, Co, Ni) have been examined crystallographically using single-crystal X-ray diffraction at 1 bar and temperatures down to 15 K, by means of applying open He cryojet techniques at in-house laboratory instrumentation. All four representative phases show a comparable, highly anisotropic thermal expansion behavior with a remarkable negative thermal expansion along the monoclinic b axis and a pronounced anisotropic expansion perpendicular to it. The lattice changes down to 15 K correspond to an 'inverse thermal pressure' of approximately 0.7 GPa, which is far below the critical pressures of transition under hydrostatic compression (Pc≥ 2.40 GPa). Consequently, no equivalent structural phase transition was observed for any compound, and neither dehydration nor rearrangements of the hydrogen bonding schemes have been observed. The M2+SO4·H2O (M2+= Mg, Fe, Co, Ni) end-member phases preserve the kieserite-type C2/c symmetry; hydrogen bonds and other structural details were found to vary smoothly down to the lowest experimental temperature. These findings serve as an important basis for the assignment of sulfate-related signals in remote-sensing data obtained from orbiters at celestial bodies, as well as for thermodynamic considerations and modeling of properties of kieserite-type sulfate monohydrates relevant to extraterrestrial sulfate associations at very low temperatures.

KW - Galilean icy moons

KW - He cryojet techniques

KW - monohydrate sulfate kieserites

UR - http://www.scopus.com/inward/record.url?scp=85126481112&partnerID=8YFLogxK

U2 - 10.1107/S2052252521012720

DO - 10.1107/S2052252521012720

M3 - Article

C2 - 35371501

AN - SCOPUS:85126481112

VL - 9

SP - 194

EP - 203

JO - IUCrJ

JF - IUCrJ

SN - 2052-2525

ER -