The primary substance that makes up the Earth’s atmosphere is nitrogen, which accounts for about 78% of the atmosphere's composition. The atmosphere also consists of approximately 21% oxygen, along with trace amounts of argon, carbon dioxide, and other gases. This mixture is vital for life on Earth, as it provides the necessary oxygen for respiration and protects the planet from harmful solar radiation. Additionally, the atmosphere plays a key role in weather patterns and climate regulation, making it an essential component of Earth's environmental systems.