AMORPHOUS SOLID WATER (ASW) is a flash-frozen, non- crystalline form of water which occurs when water vapor strikes a very cold (below 140 K) surface. Although this disorderly ice does not exist naturally on Earth, it may well constitute the vast majority of water in the universe, where conditions are mostly chillier than 140 K. For this reason, and because ASW represents a sort of completely-slowed-down version of liquid water, scientists at the Pacific Northwest National Lab (Bruce Kay, 509-376-0028, bd_kay@pnl.gov) have studied amorphous ice in their lab. They assemble an ASW layer atop a thin film of carbon tetrachloride (cleaning fluid). When the sample is warmed above 140 K, the water molecules start to follow their hexagonal instincts by restructuring themselves into a crystalline form. The initial stage in this process is the formation of tiny randomly oriented ice crystals. As more of these crystals form, the icy overlayer starts to resemble a layer of crushed ice, and the CCl₄ molecules, with a high vapor pressure and eager to escape any way they can, start to percolate through the gaps between the grains. Following a maze of branching pathways, the molecules eventually come to the ASW surface and exit as "molecular volcanoes," analogous to the violent emergence of underground magma through fissures during a volcano. This line of research might have a bearing on the episodic release of gas from comets and other celestial bodies. (R. Scott Smith et al., upcoming article in Physical Review Letters; see figure at Physics News Graphics)

A PRESSURE STANDARD FROM QUANTUM-MECHANICAL SOUNDS may be possible, Berkeley researchers reported at last month's Acoustical Society of America meeting. Applying pressure to a superfluid--an ultra cold liquid with zero resistance to flow--can cause it to move through a tiny hole and emit sounds at a characteristic frequency. The sound is created when the superfluid sheds energy in the form of "quantum vortices" whose size and other properties depend on precisely known quantum mechanical constants. The Berkeley physicists, who recently used helium-4 superfluids to measure the Earth's rotation rate (Update 318), said their setup can potentially determine pressure from the sound frequency if they can minimize temperature fluctuations which create additional unwanted vortices. (ScienceNOW, June 18, 1997).

THE STEREODYNAMICS OF MOLECULES, the orientation and movement of molecules in three-dimensional space, plays a large role in chemical reactions. As with cosmonauts approaching their space station, some maneuvers are more effective than others in producing a successful docking. In the case of diatomic hydrogen molecules approaching a copper surface, an IBM Almaden/UC Santa Barbara collaboration has shown that the molecules have a much better chance of crash landing and then sticking to the surface if the plane of the molecule (traced out by the mutual orbit of the two atoms about each other) is parallel to the surface. The reaction process was also observed to favor certain molecule kinetic energies over others. Quantitative studies of stereo preferences should lead to a better understanding of catalysis and other industrially important processes where chemical reactions are influenced by nearby surfaces. (H. Hou et al., Science, 4 July 1997.)