MERCURY

Mercury, the smallest and innermost planet in our solar system, is a world of extremes. Named after the Roman messenger god for its rapid movement across the sky, Mercury completes its orbit around the Sun in just 88 Earth days—the shortest year of any planet.

This rocky planet experiences the most extreme temperature variations in the solar system, ranging from -173°C (-280°F) at night to 427°C (800°F) during the day. Mercury's surface resembles Earth's Moon, pockmarked with craters from countless impacts over billions of years.

Despite its proximity to the Sun, Mercury may harbor water ice in permanently shadowed craters at its poles. The planet has a surprisingly large iron core, making up about 85% of its radius, which generates a weak magnetic field—unique among the solar system's small, rocky planets.