Its exact date of discovery is still uncertain. Civilizations have known about mercury for thousands of years as it can be seen with the naked eye. It was first observed through a telescope by Galileo Galilei.
Mercury formed 4.5 billion years ago. It is the smallest of all the planets and is the first planet from the Sun. It is approximately 4800 km wide, 1/3 size of Earth and 1.4 times bigger than the moon. Mercury was named after the Roman Deity named Mercury. Mercury was the messenger of the gods.
A day on Mercury is approximately 58 Earth days long. It also has the shortest orbital period of 88 days. The planet is tidally locked to the Sun with a 3:2 spin-orbit resonance. This means that the planet rotates thrice for every two revolutions. (2 revolutions is 176 days long, and three rotations take 176 days as well).
The temperature on Mercury during day can reach up to 430 degree Celsius. During nighttime, the temperature can be as low as -180 degree Celsius. Mercury is the second hottest planet in the solar system after Venus. How is Venus the hottest planet? Unlike Mercury, Venus has an atmosphere filled with greenhouse gases. These gases trap the heat and contain them within the planet. This makes Venus very hot.
Mercury’s surface resembles that of the Moon. It also has a lot of impact craters from comets and asteroids, just like the Moon.
Inner Layers of Mercury
Mercury is made up of 3 main layers: the core, the mantle and the crust.
The core is of 2 parts: a solid inner core and a molten outer core. The core of mercury has the highest iron content of any other planet in the solar system. Its core is approximately 4200 km wide (85% of total diameter). The molten iron in the core might be the reason for the origin Mercury’s magnetic field. This magnetic field is 1% as powerful as Earth’s magnetic field.
The planet also has a rocky mantle and a solid crust that are 400 km wide together