The glassy states of water are of common interest as the majority of H 2 O in space is in the glassy state and especially because a proper description of this phenomenon is considered to be the key to our understanding why liquid water shows exceptional properties, different from all other liquids. The occurrence of water's calorimetric glass transition of low-density amorphous ice at 136 K has been discussed controversially for many years because its calorimetric signature is very feeble. Here, we report that high-density amorphous ice at ambient pressure shows a distinct calorimetric glass transitions at 116 K and present evidence that this second glass transition involves liquid-like translational mobility of water molecules. This "double T g scenario" is related to the coexistence of two liquid phases. The calorimetric signature of the second glass transition is much less feeble, with a heat capacity increase at T g,2 about five times as large as at T g,1 . By using broadband-dielectric spectroscopy we resolve loss peaks yielding relaxation times near 100 s at 126 K for low-density amorphous ice and at 110 K for high-density amorphous ice as signatures of these two distinct glass transitions. Temperature-dependent dielectric data and heating-rate-dependent calorimetric data allow us to construct the relaxation map for the two distinct phases of water and to extract fragility indices m = 14 for the low-density and m = 20-25 for the high-density liquid. Thus, low-density liquid is classified as the strongest of all liquids known ("superstrong"), and also high-density liquid is classified as a strong liquid.

Many acronyms are used in the literature for describing different kinds of amorphous ice, mainly because many different preparation routes and many different sample histories need to be distinguished. We here introduce these amorphous ices and discuss the question of how many of these forms are of relevance in the context of polyamorphism. We employ the criterion of reversible transitions between amorphous "states" in finite intervals of pressure and temperature to discriminate between independent metastable amorphous "states" and between "substates" of the same amorphous "state". We argue that the experimental evidence suggests we should consider there to be three polyamorphic "states" of ice, namely low-(LDA), high-(HDA) and very high-density amorphous ice (VHDA). In addition to the realization of reversible transitions between them, they differ in terms of their properties, e.g., compressibility, or number of "interstitial" water molecules. Thus they cannot be regarded as structurally relaxed variants of each other and so we suggest considering them as three distinct megabasins in an energy landscape visualization.

Against all odds: Carbonic acid molecules were trapped from the gas phase in a solid noble‐gas matrix at <10 K and studied by IR spectroscopy. The 2H and and 13C isotopologues were also examined. Gas‐phase carbonic acid is thought to exist as a 1:10:1 mixture of two monomeric conformers and the cyclic dimer (H2CO3)2. This data is vital in the search for gas‐phase carbonic acid in astrophysical environments.

Dilatometry experiments on low-and high-density amorphous ices up to 0.30 GPa are presented together with powder x-ray diffraction data. Repeated isobaric heating and cooling cycles reveal three competing processes: irreversible (micro)structural relaxation, reversible relaxation, and (irreversible) crystallization. The third and subsequent heating runs produce identical curves, i.e., irreversible relaxation is absent. We interpret the deviation from linear expansivity in these curves as the onset temperature of the volumetric glass-to-liquid transition (T g, onset ) and report its dependence on pressure.