The Earth's atmosphere is as large as it is invisible. A huge bubble of gases surrounds the Earth that humans and animals rely on to stay alive, but do not see or interact with consciously. Despite this invisibility, there's a lot more to the Earth's atmosphere than just oxygen. It's a complex cocktail of gases, each contributing to the atmosphere that's vital to survival.
Nitrogen is a colorless, odorless, tasteless and inert gas that accounts for 78 percent of the Earth's atmosphere. It's present in all living organisms on the planet and the nitrogen cycle allows scientists to trace the movement of the gas from the atmosphere into the soil, flora and fauna which then decompose and release it back into the atmosphere. It's also present in the base pairs that make up nucleic acid, making it an essential component for life.
Oxygen is the second most abundant gas in the atmosphere but the third most abundant chemical in the universe, after hydrogen and helium. Oxygen is prevalent in the Earth's air, sea and land, accounting for a remarkable 88.8 percent of the mass of the Earth's oceans. It is colorless and odorless and accounts for 21 percent of the atmosphere and 23 percent of its mass.
Argon takes up 0.93 percent of the Earth's atmosphere, making it the third most common gas. It's colorless, odorless and tasteless and is inert under most conditions. It accounts for 1.28 percent of the mass of the Earth's atmosphere. Almost all the Argon in the Earth's atmosphere is argon-40. This is an isotope of the potassium-40 in the Earth's crust that decays over the course of its half-life and releases the gas into the atmosphere.
Carbon dioxide is an essential part of the process of photosynthesis: plants drawing in the gas and releasing oxygen in its stead. Despite this essential role, carbon dioxide only accounts for 0.0387 percent of the Earth's atmosphere. The gas is colorless and odorless, and the amount of it in the atmosphere fluctuates seasonally, depending on the growing season in the Northern Hemisphere. This is due to the fact the Northern Hemisphere has more land mass and, as a result, more vegetation to photosynthesize the gas.