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Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 19% of Earth's radius [0.7% of volume] or 70% of the Moon 's radius. [32][33] The inner core was discovered in 1936 by Inge Lehmann and is generally composed primarily of iron and some nickel.
core–mantle boundary. outer core–inner core boundary. Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth’s radius or 70% of the Moon 's radius. [1][2] There are no samples of Earth's core accessible for direct ...
Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust.
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.
Tardigrades are usually about 0.5 mm (0.020 in) long when fully grown. [ 2 ] They are short and plump, with four pairs of legs, each ending in claws (usually four to eight) or suction disks. [ 2 ][ 15 ] Tardigrades are prevalent in mosses and lichens and feed on plant cells, algae, and small invertebrates.
Biological roles of the elements. A large fraction of the chemical elements that occur naturally on the Earth's surface are essential to the structure and metabolism of living things. Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [1]
Last universal common ancestor. The last universal common ancestor (LUCA) is the hypothesized common ancestral cell from which the three domains of life, the Bacteria, the Archaea, and the Eukarya originated. The cell had a lipid bilayer; it possessed the genetic code and ribosomes which translated from DNA or RNA to proteins.
Earth's outer core. Earth's outer core is a fluid layer about 2,260 km (1,400 mi) thick, composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [1][2][3] The outer core begins approximately 2,889 km (1,795 mi) beneath Earth's surface at the core-mantle boundary and ends 5,150 km (3,200 mi) beneath ...