Mercury
Discover the secrets of Mercury, the closest planet to the Sun. Despite its small size, Mercury fascinates astronomers with its mysterious beauty. Known as the "Swift Messenger of the Gods," Mercury's unique dance through space leaves us spellbound.
Small and Speedy
Mercury is only slightly bigger than the Moon and it zooms around the Sun at around 29 miles per second or 47 kilometers per second. This is because the closer a planet is to the Sun, the faster it travels. Due to Mercury being so close to the Sun, the Sun would appear three times as big compared to the Sun in Earth’s sky. This also leads to extreme temperatures on the small planet day and night, since there is no atmosphere to retain heat. During the day, it can get as high as 800 degrees Fahrenheit or 430 degrees Celsius and during the night as low as -290 degrees Fahrenheit or -180 degrees Celsius.
Mercury Stats
Equator circumference: 15,329km
Radius: 2,440km
Average distance from Sun: 58 million km
Surface temperature: -180°C to 430°C
Day length: 59 Earth days
Year length: 88 Earth days
Average orbital speed: 170,500km/h (47km/s)
Moons: 0
Planet type: terrestrial
Mercury has a very odd, egg-shaped (elliptical) orbit around the Sun. This can take Mercury as close as 29 million miles or 47 million kilometers from the Sun to as far as 43 million miles or 70 million kilometers. While it speeds around the Sun at 47 kilometers per second, it is very slowly rotating on its axis, completing a rotation every 59 Earth days. This means it does not even complete two full days before doing its full 88-day orbit! This gives Mercury something called a 3:2 spin-orbit resonance, meaning it rotates on its axis exactly three times for every 2 orbits. Due to this weird orbit and rotation, the Sun may appear to rise, then set, and then rise again pretty quickly if you were standing on some parts of Mercury’s surface. In the video model of the orbit to the right, you can see the eccentric orbit and rotation. You can even see how Mercury speeds up when it is closer to the Sun due to the stronger gravitation in closer proximity.
Odd Orbit
You can see from the image below how Mercury’s surface is like that of the Moon’s. There are many impact craters from collisions by comets and meteoroids. Since Mercury does not really have an atmosphere (a very thin exosphere), space objects like asteroids will not burn up when heading towards the surface, leaving Mercury more prone for collisions. It is thought that in some of the deep craters in permanent shadows, there may be water ice since these areas could be cold enough to preserve it.
Structure and Surface
IRON
Mercury is the second densest planet in the solar system with a large metallic, mainly iron core that makes up 85% of the planet’s radius. This core would extend about 1,289 miles or 2,074 kilometers before reaching the mantle and crust, which combined are only about 250 miles or 400 kilometers thick. The mantle and crust are mainly composed of silicate (consisting of silicon and oxygen).
The first spacecraft that visited Mercury was NASA’s Mariner 10, launched in 1974. This spacecraft was sent on a flyby mission, in which it imaged about 45% of Mercury's surface. NASA’s MESSENGER also flew by Mercury three times and orbited it for four years before it ended its mission by crashing into Mercury’s surface. The current mission, called BepiColombo, was launched by The European Space Agency and JAXA and has already captured views of Mercury and will continue on its mission into the future.
Missions
Mariner 10 Image
BepiColombo Image
MESSENGER’s more than 80,000 images were put together to form a 100% view of Mercury’s surface.
Why are these pictures so colorful?
These colorful images of Mercury’s surface were taken by the MESSENGER spacecraft using color base map imaging. This was done in order to enhance the differences between the rocks that make up Mercury’s surface in order to get an idea of its composition. For example, the blue hues are younger areas of Mercury’s surface while darker hues are older, more beaten up areas. This can also tell us how recently certain craters formed and the chemical composition of certain areas.
