What is the composition of the Earth?

Answer 1

Earth's solid mass is about 32% iron, 30% oxygen, 15% silicon, 14% magnesium, 3% sulfur, 2% nickel, 1.5% calcium, and 1.4% aluminum. Much of the iron and nickel are in the planetary core, which is 89% iron and 6% nickel. The atmosphere consists of 78% nitrogen and 21% oxygen, with traces of other gases including carbon dioxide (0.3%).

Earth's gravity is insufficient to hold onto high-atmosphere hydrogen and helium, so it has no thick, dense hydrogen atmosphere like the 4 larger planets. Since the planet's formation, comets have deposited water on Earth to provide hydrogen. Helium has been replaced through the decay of radioactive elements in the crust, and is normally found in underground methane deposits.

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