¹Shaunna M. Morrison, ¹Robert M. Hazen
American Mineralogist 105, 1508-1535 Link to Article [http://www.minsocam.org/msa/ammin/toc/2020/Abstracts/AM105P1508.pdf]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U. S. A.
Copyright: The Mineralogical Society of America

The evolutionary system of mineralogy relies on varied physical and chemical attributes, including
trace elements, isotopes, solid and fluid inclusions, and other information-rich characteristics, to understand processes of mineral formation and to place natural condensed phases in the deep-time context
of planetary evolution. Part I of this system reviewed the earliest refractory phases that condense at T > 1000 K within the turbulent expanding and cooling atmospheres of highly evolved stars. Part II considers the subsequent formation of primary crystalline and amorphous phases by condensation in three distinct mineral-forming environments, each of which increased mineralogical diversity and distribution prior to the accretion of planetesimals >4.5 billion years ago.
(1) Interstellar molecular solids: Varied crystalline and amorphous molecular solids containing primarily H, C, O, and N are observed to condense in cold, dense molecular clouds in the interstellar medium (10 < T < 20 K; P < 10–13 atm). With the possible exception of some nanoscale organic condensates preserved in carbonaceous meteorites, the existence of these phases is documented primarily by telescopic observations of absorption and emission spectra of interstellar molecules in radio, microwave, or infrared wavelengths. (2) Nebular and circumstellar ice: Evidence from infrared observations and laboratory experiments suggest that cubic H2O (“cubic ice”) condenses as thin crystalline mantles on oxide and silicate dust grains in cool, distant nebular and circumstellar regions where T ~100 K. (3) Primary condensed phases of the inner solar nebula: The earliest phase of nebular mineralogy saw the formation of primary refractory minerals that solidified through high-temperature condensation (1100 < T < 1800 K; 10–6 < P < 10–2 atm) in the solar nebula more than 4.565 billion years ago. These earliest mineral phases originating in our solar system formed prior to the accretion of planetesimals and are preserved in calcium-aluminum-rich inclusions, ultra-refractory inclusions, and amoeboid olivine aggregates.

¹Dominik Talla,¹Madeleine Balla, Claudia Aicher,¹Christian L. Lengauer,¹Manfred Wildner
American Mineralogist 105, 1472-1489 Link to Article [http://www.minsocam.org/msa/ammin/toc/2020/Abstracts/AM105P1472.pdf]
¹Institut für Mineralogie und Kristallographie, Althanstrasse 14, 1090 Wien, Austria
Copyright: The Mineralogical Society of America

The investigation of the presence and role of sulfates in our solar system receives growing attention because these compounds play a crucial role in the water budget of planets such as Mars and significantly influence melting equilibria on the icy moons of Saturn and Jupiter, leading to the formation of subsurface oceans and even cryovolcanism. Despite the dominant presence of higher sulfate hydrates such as epsomite, MgSO4·7H2O, and mirabilite, Na2SO4·10H2O, on these moons’ surfaces, it is not excluded that lower-hydrated sulfates, such as kieserite, MgSO4·H2O, are also present, forming from higher hydrates under pressures relevant to the mantle of the icy moons. Given the composition of the
soluble fraction in C1 and C2 chondritic meteorites, which are high in Ni content and also considered to represent the composition of the rocky cores of the Jovian icy moons, the actual compositions of potentially present monohydrate sulfates likely lie at intermediate values along the solid-solution series between kieserite and transition-metal kieserite-group end-members, incorporating Ni in particular. Moderate Ni contents are also probable in kieserite on Mars due to the planet’s long-term accumulation
of meteoritic nickel, although likely to a much lesser extent than Fe.
Structural and spectroscopic differences between the pure Mg- and Ni-end-members have been previously documented in the literature, but no detailed crystal chemical and spectroscopic investigation along the Mg-Ni solid solution has been done yet. The present work proves the existence of
a continuous (Mg,Ni)SO4·H2O solid-solution series for the first time. It provides a detailed insight into the changes in lattice parameters, structural details, and positions of prominent bands in infrared
(transmission, attenuated total reflectance, diffuse reflectance) and Raman spectra in synthetic samples as the Ni/Mg ratio progresses, at both ambient as well as low temperatures relevant for the icy moons
and Mars. UV-Vis-NIR crystal field spectra of the Ni end-member also help to elucidate the influence of Ni2+-related bands on the overtone- and combination modes.
The (Mg,Ni)SO4·H2O solid-solution series shows Vegard-type behavior, i.e., lattice parameters as well as spectral band positions, change along linear trends with increasing Ni content. Infrared spectra reveal significant changes in the wavenumber positions of prominent bands, depending on the Ni/Mg ratio. We show that the temperature during measurement also has an influence on band position, mainly in the case of H2O-related bands. The changes observed for several absorption features in the
IR spectra enable rough estimation of the Ni/Mg ratio in the monohydrate sulfate, which is applicable to present and future remote sensing data, as well as in situ measurements on Mars or the icy moons.
The spectral features most diagnostic of composition are the vibrational stretching modes of the H2O molecule and a band unique to kieserite-group compounds at around 900 cm–1 in the IR spectra, as well as the pronounced ν3 and ν1 sulfate stretching modes visible in Raman spectra.