The discussion revolves around the properties and implications of ice VII, a high-pressure phase of ice, particularly in relation to its nucleation processes and potential effects on extraterrestrial environments. Participants explore the scientific background, historical context, and experimental findings related to ice VII and its formation mechanisms.
Participants express differing views on the novelty of ice VII and its implications. While some acknowledge the recent paper's contributions, others emphasize the existence of prior research and findings. The discussion remains unresolved regarding the broader implications of ice VII formation and the specifics of its nucleation processes.
Some participants mention limitations in accessing the original Physical Review Letters paper due to copyright restrictions, which may affect the depth of discussion on the experimental details and findings.
Kurt Vonnegut's 1963 novel Cat's Cradle introduced the world to so-called "Ice Nine," a fictional form of water that freezes at room temperature. If it so much as touches a drop of regular water, that will freeze, too, and so on, spreading so rapidly that it freezes everything that comes into contact with it.
Fortunately for Earth, Ice-Nine doesn't exist. But there is an exotic form of ice dubbed "ice VII" that physicists can create in the laboratory. It's harmless in terrestrial conditions. But on an ocean world like Jupiter's moon, Europa, it could behave just like Ice-Nine under the right conditions, freezing an entire world within hours—with some key implications for the possibility of finding life on distant exoplanets. Now we know more about just how that special freezing process occurs, according to a recent paper in Physical Review Letters.
ABSTRACT
The fundamental study of phase transition kinetics has motivated experimental methods toward achieving the largest degree of undercooling possible, more recently culminating in the technique of rapid, quasi-isentropic compression. This approach has been demonstrated to freeze water into the high-pressure ice VII phase on nanosecond timescales, with some experiments undergoing heterogeneous nucleation while others, in apparent contradiction, suggest a homogeneous nucleation mode. In this study, we show through a combination of theory, simulation, and analysis of experiments that these seemingly contradictory results are in agreement when viewed from the perspective of classical nucleation theory. We find that, perhaps surprisingly, classical nucleation theory is capable of accurately predicting the solidification kinetics of ice VII formation under an extremely high driving force (|Δμ/kBT|≈1) but only if amended by two important considerations: (i) transient nucleation and (ii) separate liquid and solid temperatures. This is the first demonstration of a model that is able to reproduce the experimentally observed rapid freezing kinetics.