Mercury

Mercury: The Smallest and Fastest Planet

Mercury is the innermost planet of our solar system, orbiting closest to the Sun. Despite its proximity, it is not the hottest planet, but it does experience the most extreme temperature swings.

• Daytime temperatures soar to 427°C (800°F), hot enough to melt lead.
• Nighttime temperatures plummet to -173°C (-280°F), colder than any place on Earth.

This is due to Mercury's lack of a substantial atmosphere, which means there is nothing to trap the Sun's heat or insulate the planet at night. Its surface is a battered landscape of craters, cliffs, and mysterious shallow depressions called hollows that continue to puzzle scientists.

Structure & Composition

Mercury is unique for its massive iron core, which makes up about 85% of the planet's volume. The crust is thin and silicate-rich, and the planet is slowly shrinking as its core cools, causing the surface to buckle and crack.

Rotation & Orbit

Mercury races around the Sun in just 88 Earth days, making it the fastest planet. However, it rotates so slowly that a single day on Mercury (sunrise to sunrise) lasts 176 Earth days. This means that a year on Mercury is shorter than its day!

Interesting Facts

• Mercury has no moons and almost no atmosphere (just a thin exosphere of oxygen, sodium, hydrogen, helium, and potassium).
• Despite its harsh environment, water ice has been detected in craters at its poles, permanently shadowed from the Sun.
• Mercury's surface is marked by scarps—huge cliffs formed as the planet contracts.

Mercury is a world of searing heat, freezing cold, and cosmic extremes—a testament to the violent and beautiful diversity of our solar system.