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Photograph showing details of an ice cube under magnification. Ice I h is the form of ice commonly seen on Earth. Phase space of ice I h with respect to other ice phases. Virtually all ice in the biosphere is ice I h (pronounced: ice one h, also known as ice-phase-one).
Ice is abundant on the Earth's surface, particularly in the polar regions and above the snow line, where it can aggregate from snow to form glaciers and ice sheets. As snowflakes and hail, ice is a common form of precipitation, and it may also be deposited directly by water vapor as frost.
A snowflake is a single ice crystal that is large enough to fall through the Earth's atmosphere as snow. [ 1 ] [ 2 ] [ 3 ] Snow appears white in color despite being made of clear ice. This is because the many small crystal facets of the snowflakes scatter the sunlight between them.
The symmetric shapes are due to depositional growth, which is when ice forms directly from water vapor in the atmosphere. [5] Small spaces in atmospheric particles can also collect water, freeze, and form ice crystals. [6] [7] This is known as nucleation. [8] Snowflakes form when additional vapor freezes onto an existing ice crystal. [9] [10]
Water is a well-known example of such a material. For example, water ice is ordinarily found in the hexagonal form ice I h, but can also exist as the cubic ice I c, the rhombohedral ice II, and many other forms. Polymorphism is the ability of a solid to exist in more than one crystal form. For pure chemical elements, polymorphism is known as ...
The mass of Earth's oceans is estimated to be 1.37 × 10 21 kg, which is 0.023% of the total mass of Earth, 6.0 × 10 24 kg. An additional 5.0 × 10 20 kg of water is estimated to exist in ice, lakes, rivers, groundwater, and atmospheric water vapor. [20] A significant amount of water is also stored in Earth's crust, mantle, and core.
There are two ice giants in the Solar System: Uranus and Neptune. In astrophysics and planetary science the term "ice" refers to volatile chemical compounds with freezing points above about 100 K, such as water, ammonia, or methane, with freezing points of 273 K (0 °C), 195 K (−78 °C), and 91 K (−182 °C), respectively (see Volatiles).
The composition of the ice will vary. For example, Earth's polar caps are mainly water ice, whereas Mars's polar ice caps are a mixture of solid carbon dioxide and water ice. Polar ice caps form because high-latitude regions receive less energy in the form of solar radiation from the Sun than equatorial regions, resulting in lower surface ...