Nicknamed “The Swiftest Planet”, Mercury is the first planet from the Sun. Named after the Roman god of messages, Mercury lives up to its name.
Mercury is a terrestrial planet. Terrestrial planets are only found in the inner solar system, the area between the Sun and the asteroid belt. All terrestrial planets contain a rocky core and solid surface.
Mercury has a radius of 1,516 miles and is 1/3rd the width of Earth. That’s slightly bigger than our moon, which is only 1/4th the size of Earth.
One day on Mercury takes 176 Earth days, while one year on Mercury takes 88 Earth days. In other words, one full day takes over a year. With the short year, the nickname of “The Swiftest Planet” starts to make sense.
Mercury has no tilt to it. This means it does not have any seasons like Earth does. It orbits in the same direction as Earth, but the shape of Mercury’s orbit is somewhat egg shaped. Because Mercury’s orbit varies from 29 to 43 million miles away from the Sun, light from the Sun only takes 3.2 minutes to reach Mercury.
Mercury has a core. The core is 1,289 miles in radius and takes up about 85% of the planet’s overall radius. The core may be molten. Because of the cooling of the core, Mercury is shrinking. This causes quakes, just like Earthquakes. Because of the big core, the mantle and crust make up only 15% of planet’s radius.
Mercury does not have atmosphere, but is covered in an exosphere. Made up of oxygen, sodium, hydrogen, helium, and potassium, it is too thin to breathe. The exosphere is strongly affected by solar winds.
The Sun looks three times larger on Mercury than from Earth. It is also 11 times brighter than on Earth.