Earth 🜨

Earth's atmosphere is composed of roughly 78 percent nitrogen, 21 percent oxygen, and trace amounts of argon, carbon dioxide, water vapor, and other gases. This unique composition sustains all known life and provides a protective blanket against harmful solar radiation. The ozone layer in the stratosphere absorbs most ultraviolet radiation, while the greenhouse effect maintains surface temperatures suitable for liquid water.

Earth is the only known planet with tectonic plate activity, which drives the formation of mountains, ocean basins, and volcanic activity. About 71 percent of the surface is covered by liquid water, and the planet maintains a strong magnetic field generated by its molten iron-nickel outer core. This magnetosphere deflects the solar wind and protects the atmosphere from erosion. Earth's single large moon stabilizes the planet's axial tilt, contributing to relatively stable seasons.

Hundreds of satellites orbit Earth for observation, communication, and scientific research. The International Space Station, the largest structure ever built in space, has been continuously occupied since November 2000. NASA's fleet of Earth-observing satellites, including Landsat, MODIS, and DSCOVR, monitors climate change, weather patterns, and environmental conditions in unprecedented detail.