Can extreme pressure and temperature transform water into a solid crystal-like state, similar to ice at the bottom of a deep ocean on a water-rich planet?

Context

The user is curious about the behavior of water under extreme conditions of pressure and temperature, such as those found at the bottom of a hypothetical ultra-deep ocean on a large, water-abundant planet. They are particularly interested in whether water can become a solid, crystal-like form due to pressure, even if the temperature isn't freezing. They are also speculating about other potential states of water beyond solid, liquid, and gas under these extreme conditions, such as a 'hot iceberg' or a glassy/crystalline structure.

Simple Answer

• Yes, extreme pressure can turn water into ice, even if it's not freezing cold.
• This ice is different from the ice you find in your freezer.
• Very deep oceans on giant water planets could have 'ice' at the bottom.
• This 'ice' would be very dense and possibly crystalline.
• Very high temperatures and pressure can create even stranger forms of water.

Detailed Answer

Water, a seemingly simple molecule, exhibits a remarkable range of phases and properties under extreme conditions of pressure and temperature. Our everyday experience confines us to observing water in its familiar solid (ice), liquid (water), and gaseous (steam) states. However, the phase diagram of water, a graphical representation of the physical states of water under varying pressures and temperatures, reveals a far more complex reality. At elevated pressures, water molecules are forced closer together, altering the intermolecular forces and prompting the formation of various solid phases, known as ice polymorphs. These ice polymorphs differ in their crystal structure and density compared to ordinary ice (ice Ih), which is what we commonly encounter. The existence of these exotic ice forms has been confirmed through laboratory experiments, where water is subjected to pressures far exceeding those found at the deepest parts of Earth's oceans. The pressure needed to form these ices is relative to the temperature of the sample and generally requires thousands of times the pressure we experience at sea level.

Imagine a planet significantly larger and more water-rich than Earth. Its oceans could extend to depths of many kilometers, subjecting the water at the bottom to immense pressure. At these depths, the pressure would be sufficient to transform water into one or more of the high-pressure ice polymorphs. Unlike the familiar ice that floats on water, these high-pressure ice forms are denser than liquid water. Consequently, they would sink to the ocean floor, forming a layer of solid ice. The precise type of ice polymorph that would form would depend on the specific pressure and temperature conditions at that depth. However, it's worth noting that the temperature at such depths might not necessarily be near freezing point. Geothermal activity within the planet's core could contribute to significant heating, potentially leading to the formation of exotic ice forms at relatively high temperatures. It is important to note that the extreme pressures needed to form exotic ices are difficult to achieve and generally outside of earth conditions.

The behavior of water under extreme pressure and temperature is not limited to the formation of high-pressure ice polymorphs. At even more extreme conditions, water can transition into a state known as superionic water. In this state, the water molecules break apart, and the oxygen atoms form a crystalline lattice while the hydrogen ions move freely through the lattice like electrons in a metal. This superionic water is predicted to exist in the interiors of ice giants like Uranus and Neptune. The existence of superionic water is supported by computer simulations and experiments, though directly observing it remains a challenge due to the extreme conditions required to create it. The extreme pressures and temperatures are difficult to recreate in a controlled laboratory setting, and therefore are studied with powerful simulations. The simulations predict unique physical properties such as superionic conductivity, which greatly exceeds those of regular water.

The concept of a 'hot iceberg' or a crystalline state of water at high temperatures, though seemingly paradoxical, touches upon the complex interplay of pressure and temperature in determining the phase of a substance. While we are accustomed to associating ice with freezing temperatures, high pressure can stabilize the solid phase of water even at temperatures well above the freezing point. However, the term 'hot iceberg' might be misleading, as the ice polymorphs formed under high pressure are structurally and physically distinct from ordinary ice. They possess different densities, melting points, and even electrical properties. Furthermore, the crystalline state of water under extreme conditions could exhibit unique properties not found in ordinary ice, potentially resembling a glassy or crystalline material with novel characteristics. The exact nature of this crystalline state would depend on the specific pressure and temperature conditions, as well as the chemical composition of the water, including the presence of dissolved salts or other impurities. The structure can drastically change the properties and behavior of the substance.

Beyond the familiar phases of solid, liquid, and gas, and the exotic states like superionic water, lies a vast realm of possibilities for water under extreme conditions. Scientists are continually exploring the phase diagram of water, both theoretically and experimentally, to uncover new phases and understand their properties. These investigations have implications for understanding the interiors of planets, the behavior of water in industrial processes, and even the origin of life. The study of water under extreme conditions highlights the remarkable versatility of this seemingly simple molecule and challenges our intuitive understanding of matter. It is worth noting that the study of water under extreme conditions is an active area of research and simulations and experiments can continue to improve our knowledge in the future. While some predicted results may only exist under laboratory conditions the possibilities give us a better understanding of how water can behave.