Low-Temperature Specific Heat Capacity of Water-Ammonia Mixtures Down to the Eutectic.

Robust thermodynamic data are essential for the development of geodynamic and geochemical models of ocean worlds. The water-ammonia system is of interest in the study of ocean worlds due to its purported abundance in the outer solar system, geological implications, and potential importance for origins of life. In support of developing new equations of state, we conducted 1 bar specific heat capacity measurements () using a differential scanning calorimeter (DSC) at low temperatures (184-314 K) and low mass fractions of ammonia (5.

Experimental Characterization of the Pyridine:Acetylene Co-crystal and Implications for Titan's Surface.

Titan, Saturn's largest moon, has a plethora of organic compounds in the atmosphere and on the surface that interact with each other. Cryominerals such as co-crystals may influence the geologic processes and chemical composition of Titan's surface, which in turn informs our understanding of how Titan may have evolved, how the surface is continuing to change, and the extent of Titan's habitability. Previous works have shown that a pyridine:acetylene (1:1) co-crystal forms under specific temperatures and experimental conditions; however, this has not yet been demonstrated under Titan-relevant conditions.

Reply to the 'Comment on Cage occupancy of methane clathrate hydrates in the ternary HO-NH-CH system' by S. Alavi and J. Ripmeester, , 2022, , DOI: 10.1039/D1CC06526B.

Our recent Communication suggested that ammonia in aqueous solution may preferentially destabilize large cages in methane clathrate hydrates. A Comment favored ammonia incorporation instead, but it did not accurately describe our proposed mechanism and relied primarily on studies conducted in different chemical systems and/or which used other preparation methods.

Cage occupancy of methane clathrate hydrates in the ternary HO-NH-CH system.

The incorporation of ammonia inside methane clathrate hydrate is of great interest to the hydrate chemistry community. We investigated the phase behavior of methane clathrate formed from aqueous ammonia solution. Ammonia's presence decreases methane occupancy in the large cages, without definitive Raman spectroscopic evidence for its incorporation inside the structure.

Raman Signatures and Thermal Expansivity of Acetylene Clathrate Hydrate.

The vibrational signatures for the υ C≡C and υ symmetric C-H stretches of acetylene in cubic structure I clathrate, synthesized under ambient pressure, are reported for the first time. The most diagnostic features are at 1966 for υ and 3353 cm for υ, respectively, and are assigned to acetylene trapped in the large 56 cages. In addition, the υ mode for acetylene occupying the small 5 cages is observed at 1972.

Titan Lakes Simulation System (TiLSS): A cryogenic experimental setup to simulate Titan's liquid hydrocarbon surfaces.

Titan's hydrocarbon lakes play an important role in the chemistry, geomorphology, and climate of the satellite. Our knowledge of their composition relies mainly on thermodynamic modeling and assumptions based on Radar and VIMS (Visible and Infrared Mapping Spectrometer) data. Several thermodynamic models have been used to calculate the composition of these lakes, and their results on even the major lake components (methane, ethane, propane, and nitrogen) exhibit large discrepancies.

Cometary science. Subsurface properties and early activity of comet 67P/Churyumov-Gerasimenko.

Heat transport and ice sublimation in comets are interrelated processes reflecting properties acquired at the time of formation and during subsequent evolution. The Microwave Instrument on the Rosetta Orbiter (MIRO) acquired maps of the subsurface temperature of comet 67P/Churyumov-Gerasimenko, at 1.6 mm and 0.

Experimental study on the effect of ammonia on the phase behavior of tetrahydrofuran clathrates.

Clathrate hydrates, ice-like crystalline compounds in which small guest molecules are enclosed inside cages formed by tetrahedrally hydrogen-bonded water molecules, are naturally abundant on Earth and are generally expected to exist on icy celestial bodies. A prototypical example is Saturn's moon Titan, where dissociation of methane clathrates, a major crustal component, could contribute significantly to the replenishment of atmospheric methane. Ammonia is an important clathrate inhibiting agent that may be present (potentially at high concentrations) in Titan's interior.

Formation of a new benzene-ethane co-crystalline structure under cryogenic conditions.

We report the first experimental finding of a solid molecular complex between benzene and ethane, two small apolar hydrocarbons, at atmospheric pressure and cryogenic temperatures. Considerable amounts of ethane are found to be incorporated inside the benzene lattice upon the addition of liquid ethane onto solid benzene at 90-150 K, resulting in formation of a distinctive co-crystalline structure that can be detected via micro-Raman spectroscopy. Two new features characteristic of these co-crystals are observed in the Raman spectra at 2873 and 1455 cm(-1), which are red-shifted by 12 cm(-1) from the υ1 (a1g) and υ11 (eg) stretching modes of liquid ethane, respectively.

Thermodynamic data and modeling of the water and ammonia-water phase diagrams up to 2.2 GPa for planetary geophysics.

We present new experimental data on the liquidus of ice polymorphs in the H(2)O-NH(3) system under pressure, and use all available data to develop a new thermodynamic model predicting the phase behavior in this system in the ranges (0-2.2 GPa; 175-360 K; 0-33 wt % NH(3)). Liquidus data have been obtained with a cryogenic optical sapphire-anvil cell coupled to a Raman spectrometer.

Thermodynamic model for water and high-pressure ices up to 2.2 GPa and down to the metastable domain.

We propose a thermodynamic model of the properties of liquid water and ices I, III, V, and VI that can be used in the ranges of 0-2200 MPa and 180-360 K. This model is the first to be applicable to all H(2)O phases in these wide ranges, which exceed the stability domain of all phases. Developing empirical or semiempirical expressions for the specific volumes of liquid water or ices has been necessary.