"Obsession" (1967).
During the Hadean Eon, earth’s first 500 million years, prior to the origin of life, an alien mineral collector may have been disappointed on the diversity of minerals found on the planet. Minerals were limited due to the lack of water and plate tectonics to minerals that could form by crystallization from magma and regional metamorphism by impacts. Comets may bring some water onto earth and now minerals formed by serpentinization, evaporation and hydrothermal alteration were possible. Mineralogists, based on such premises, have proposed a preliminary list of 420 plausible minerals for the Hadean. As earth cooled down and the meteorite bombardment ceased, water condensed from the atmosphere and the first oceans formed. Earth today is still is a water world, with large oceans, polar caps of ice, and an atmosphere rich in water vapor. Many minerals form from other minerals reacting with water or contain water in their crystalline structure. Plate tectonics constantly reshapes the planet and brings minerals formed deep within the planet to its surface. Two-thirds of Earth's minerals emerged only after the first life appeared some 3.7 billion years ago and changed forever the chemical processes occurring on earth. For example, early microorganisms released oxygen into the atmosphere. The free oxygen reacted with other elements and existing minerals, forming new ones. Since then minerals are constantly formed by volcanic and tectonic processes, water-rock interactions and biological activity. Nowadays 5,000 minerals have been found on Earth and every year some new ones are discovered.
Spessartine-Garnet on Feldspar, Shigar Valley, Pakistan.
Dutch graphic artist Maurits Cornelis Escher (1898-1972).
There are about 15,300 possible ways to combine the known elements. However, even if we didn't yet discover all terrestrial minerals, it's unlikely that all possible combinations will ever be present on our planet.
We know by analyzing the light of distant stars, that other stars, and likely star systems, display different ratios of elements if compared to our system. As the star and the planets form from the same accretion disk, knowing the chemical composition of the star can provide also some information on the orbiting planets. As the chemical composition of an alien planet will differ from the beginning, also its mineralogy will be different in the end.
The exoplanet 55 Cancri e is roughly twice Earth’s radius, but just eight times its mass. Its density is too low if compared to Earth. Earth is composed mostly of iron, oxygen, magnesium, and silicon, with some sulfur, nickel, calcium, and aluminum added to the mix. Observing the composition of the planet's host star, astronomers discovered a high concentration of carbon and oxygen. It's likely that most minerals on 55 Cancri e are based on a combination of the two elements, forming less dense minerals as terrestrial silicates. Surprisingly enough carbon minerals are rare on Earth. Just fifty have been identified on Earth and most are associated with life, forming by alteration of organic remains, like decaying biomass or derived from coal and oil. Likely here life "hijacked" carbon, so that C-minerals formed by pure inorganic processes are less common.
Alien minerals will also "evolve" together with their planet. Depending on the presence of water, type of tectonics, atmosphere or even life various minerals may form.
We know by analyzing the light of distant stars, that other stars, and likely star systems, display different ratios of elements if compared to our system. As the star and the planets form from the same accretion disk, knowing the chemical composition of the star can provide also some information on the orbiting planets. As the chemical composition of an alien planet will differ from the beginning, also its mineralogy will be different in the end.
The exoplanet 55 Cancri e is roughly twice Earth’s radius, but just eight times its mass. Its density is too low if compared to Earth. Earth is composed mostly of iron, oxygen, magnesium, and silicon, with some sulfur, nickel, calcium, and aluminum added to the mix. Observing the composition of the planet's host star, astronomers discovered a high concentration of carbon and oxygen. It's likely that most minerals on 55 Cancri e are based on a combination of the two elements, forming less dense minerals as terrestrial silicates. Surprisingly enough carbon minerals are rare on Earth. Just fifty have been identified on Earth and most are associated with life, forming by alteration of organic remains, like decaying biomass or derived from coal and oil. Likely here life "hijacked" carbon, so that C-minerals formed by pure inorganic processes are less common.
Alien minerals will also "evolve" together with their planet. Depending on the presence of water, type of tectonics, atmosphere or even life various minerals may form.
Captain Jean-Luc Picard kept a small transparent crystal on the desk in his ready room aboard the USS Enterprise-D. He often played with the small stone when he had to make an important decision. (TNG: "Conspiracy", "Where Silence Has Lease", "Suddenly Human", "A Matter of Time", "The Masterpiece Society", and more) His first officer, William T. Riker, also did so on occasion. (TNG: "Gambit, Part I")
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