Mercury
The smallest terrestrial planet in the solar system, Mercury is a dead, grey world of extremes. Scarred, wrinkled, and lacking an atmosphere, this planet has scorching hot days and freezing cold nights.
Mercury Stats
Mercury Facts |
Average Distance from Sun: 57.91 million km
Perihelion: 46 million km Aphelion: 69.82 million km Mass: 0.055 times Earth Diameter: 4879.4 km Volume: 0.056 times Earth Gravity: 0.38 times Earth (3.7 N/kg) Temperature: 467 C to -184 C Rotation: 1407.6 hours Revolution: 87.968 Earth days Type: Terrestrial planet Namesake: Mercury was the Roman god of travel and messenger of the gods. His Greek form is Hermes. |
- MERCURY'S DAY IS 175.9 EARTH DAYS. While it takes 58.65 Earth days to rotate once, if you were standing on Mercury, a day would seem to take nearly 176 Earth days! Mercury's orbit makes it seem that way, since it is so close to the Sun and with an orbit more elliptical than the other planets (except for the dwarf planets, with orbits even MORE elliptical), this makes a day on Mercury weird. On some places, the Sun seems to rise for a while, then reverse direction and sink below the horizon, before rising again and finally completing a "proper" sunset, getting smaller as it heads west in the Mercurian sky.
- MERCURY HAS A HUGE CORE. Mercury's core is unusually large, taking up 75% of the planet's diameter. It's believed that Mercury may have been much larger billions of years ago, but a collision stripped off much of the planet.
- MERCURY HAS WRINKLES. Over time, Mercury's core has shrunk and cooled, though it's still liquid iron. This caused Mercury's crust to form "wrinkles."
- MERCURY LACKS AN ATMOSPHERE. An atmosphere is a layer of gas surrounding an object. Mercury may have this layer of gas, but it's so thin and so unstable that it isn't an "atmosphere" anymore. This is called an exosphere. Mercury's exosphere is so thin that it can't fill a single party balloon!. Solar winds prevent much of these gases (mostly sodium, magnesium and oxygen) from leaving Mercury because the planet is so close to the Sun (unlike other planets like Venus, where the solar winds are ever so slightly pulling off gas).
- MERCURY IS SCARRED. Without a proper atmosphere to burn up asteroids and meteoroids, Mercury has been battered by so many craters. The largest crater, Caloris Basin, is 1550 km in diameter! That's 32% of Mercury's diameter!
- MERCURY IS GREY. The closest planet to the Sun is often mistaken to be brown, orange, yellow or red, but Mercury is in fact, grey (if not just a TINY bit brownish)! The surface of the planet's composition would actually make it a dark grey, but it appears much paler because it's so close to the Sun!
- MERCURY'S ROTATION IS SLOWING DOWN. Being so close to the Sun, the Sun's gravity is slowly making Mercury tidally-locked, where one rotation is equivalent to one revolution. If you want an example of an object that is tidally-locked, look no farther than the Moon! One side of the Moon is always facing Earth, and in the far future, one side of Mercury will always be facing the Sun!