Description

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Context

The discovery of Plastic Ice VII using neutron scattering experiments highlights how water behaves under extreme planetary conditions influencing planetary science, space exploration & high-pressure material research.

Key Highlights

Scientists have confirmed existence of Plastic Ice VII unique high pressure phase of water where molecules rotate freely within rigid crystalline structure.

Forms at pressures exceeding 3 GPa (30,000 times Earth atmospheric pressure) & temperatures above 450 K (177°C).

Initially theorized in 2008 its existence was verified using quasi-elastic neutron scattering (QENS) & diamond-anvil cell experiments.

Found in extreme planetary environments such as deep within icy moons of Jupiter (Ganymede, Callisto) & Saturn (Titan) reshaping understanding of water role in space.

Insights from Plastic Ice VII could impact materials science, planetary exploration, high-pressure technology development.

Suggests that water in extreme conditions behaves in more complex ways than previously known influencing models of exoplanets & celestial body structures.

What is Plastic Ice VII?

Plastic Ice VII is an exotic phase of ice that behaves as hybrid between solid ice & liquid water.

It forms under extreme high-pressure & high-temperature conditions where water molecules remain in fixed crystalline structure but can rotate freely similar to liquid molecules. This unique property makes it more malleable, hence term plastic ice.

Formation Conditions

Pressure: Above 30,000 bars (3 GPa), nearly 30 times the pressure at the deepest point of Earth oceans.

Temperature: Above 177°C (450K)

Crystal Structure: Cubic lattice similar to Ice VII but with rotational molecular movement.

Scientists at the Institut Laue-Langevin (ILL) in France used quasi-elastic neutron scattering (QENS) & diamond-anvil cells to analyze high-pressure samples.

Neutron Scattering Technique: A neutron beam was fired at the water sample & scientists measured how neutrons lost or gained energy based on molecular motion.

Molecules in Plastic Ice VII rotated in jerky manner constantly breaking & reforming hydrogen bonds rather than rotating smoothly.

Jupiter & Saturn icy moons (e.g. Europa, Ganymede, Titan) may have contained Plastic Ice VII during their early evolution. This phase could still exist in deep oceans of exoplanets with high-pressure environments.

If Plastic Ice VII can incorporate salts into its structure it may influence ocean chemistry on alien worlds. Could provide insights into nutrient cycles in extraterrestrial oceans.

May help in designing high-pressure-resistant materials. Potential applications in futuristic pressure-based technology.

Quasi-Elastic Neutron Scattering (QENS)

QENS is technique used to study the motion of molecules at the atomic scale particularly useful for analyzing diffusion, rotations, vibrations.

A neutron beam is fired at the sample. As neutrons scatter off the water molecules they either gain or lose energy depending on movement of the molecules.

By measuring energy changes scientists can determine how molecules move, rotate or vibrate in given phase of ice.

Moons of Jupiter & Saturn

Jupiter’s Moons	Key Features	Potential for Plastic Ice VII
Europa	Subsurface ocean, thin ice crust, strong tidal forces	High pressure beneath ice layer may have hosted Plastic Ice VII in the past
Ganymede	Largest moon, has a magnetic field, deep internal ocean	Likely had Plastic Ice VII during early evolution
Callisto	Oldest, heavily cratered surface, underground ocean suspected	Potential for deep high-pressure layers with exotic ice phases

Saturn’s Moons	Key Features	Potential for Plastic Ice VII
Titan	Thick atmosphere, lakes of methane and ethane, suspected underground ocean	Deep ocean could have regions of high pressure forming Plastic Ice VII
Enceladus	Ice-covered surface, geysers ejecting water vapor, strong evidence of a subsurface ocean	Possible deep layers where Plastic Ice VII existed
Dione	Tectonic features, potential underground ocean	Could have transient phases of Plastic Ice VII

Exoplanets

Exoplanets (or extrasolar planets) are planets that orbit stars outside our solar system.

They are found in distant star systems & can have wide range of characteristics from rocky Earth-like planets to gas giants larger than Jupiter.

Type	Description
Terrestrial (Rocky) Exoplanets	Earth-like planets with solid surfaces (e.g., Proxima Centauri b)
Gas Giants	Large planets with thick atmospheres of hydrogen & helium (e.g., WASP-12b)
Super-Earths	Planets larger than Earth but smaller than Neptune, possibly rocky or icy (e.g., Kepler-22b)
Mini-Neptunes	Smaller versions of Neptune with thick atmospheres (e.g., K2-18b)
Ocean Worlds	Planets covered by deep oceans, possibly with subsurface ice (e.g., Europa-like exoplanets)
Rogue Planets	Planets that don’t orbit a star and drift in space (e.g., CFBDSIR 2149-0403)

Why is it Called Plastic Ice VII?

Plastic Behavior

Unlike normal ice Plastic Ice VII has a structure that is both solid & deformable.

The water molecules are locked in a fixed crystalline lattice (like a solid) but they can rotate freely (like a liquid).

This makes it more malleable & adaptable similar to plastics which can be reshaped without breaking.

The new phase is modified version of Ice VII known high-pressure ice phase.

Ice VII forms under extreme pressure (above 20,000 bars) & has dense cubic structure where molecules are tightly packed.

In Plastic Ice VII cubic structure is maintained but molecules start rotating making it hybrid phase between solid & liquid.

Property	Ice VII	Plastic Ice VII
Molecular Motion	Fixed, no rotation	Free rotation, like in liquids
Structure	Rigid cubic lattice	Cubic lattice, but molecules rotate
Pressure Needed	> 20,000 bars	> 30,000 bars
Temperature Needed	0 - 100°C	177 - 326°C
Flexibility	Hard, brittle	Soft, moldable (plastic-like)

Sources:

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PRACTICE QUESTION

Q. Discuss importance of discovery of Plastic Ice VII in understanding water behavior under extreme conditions & its implications for planetary science & materials research.