Mercury is the both the closest planet to the Sun (4,878km wide), and the smallest planet in the solar system, similar in size to our Moon (3475.6km wide) and 2/5 the size of Earth.
Here are some more interesting facts about the planet Mercury:
Orbit: Mercury orbits the Sun quicker than all other planets in our solar system with its speed caused by the Sun’s powerful gravitational pull. The planet’s quick motion through the sky has seen it associated with Mercury, the speedy messenger of the gods from Roman mythology.
Day/Year: A year on Mercury is around 88 days long, but one full day (from sunset to sunrise) takes 176 days.
Structure: Mercury has an iron core, and a magnetic field strong enough to repel the solar winds. Its wrinkled surface features, known as Lobate Scarpes, are a result of the cooling and contraction of its core, with Mercury’s many craters formed after numerous encounters with asteroids and comets.
Viewing: Mercury is known as the “elusive planet” because its close proximity to the Sun doesn’t allow for nighttime viewing. As the Sun sets so does Mercury, therefore it is best viewed an hour before sunrise or sunset from the Earth’s perspective. When observed through a telescope, Mercury can be seen going through phases like the Moon and appears as a bright, blue spot of light.
Missions: Mariner 10 passed by Mercury three times from 1974 to 1975 and managed to map around 45% of the planet’s surface. From 2004 to 2015, the MESSENGER spacecraft carried out further important research.