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

Manfred Wildner, Boris A. Zakharov, Nikita E. Bogdanov, Dominik Talla, Elena V. Boldyreva, Ronald Miletich

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)194-203
Number of pages10
JournalIUCrJ
Volume9
DOIs
Publication statusPublished - 1 Mar 2022

Keywords

  • Galilean icy moons
  • He cryojet techniques
  • monohydrate sulfate kieserites

OECD FOS+WOS

  • 1.03 PHYSICAL SCIENCES AND ASTRONOMY
  • 1.04 CHEMICAL SCIENCES
  • 2.05 MATERIALS ENGINEERING
  • 1.06 BIOLOGICAL SCIENCES

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