Mercury






Mercury is the closest planet to the sun. The orbit, or path, it takes around the sun is not in a circle like Earth. The path it takes is called an ellipse, which is like a circle that has been stretched out. For this reason, the distance from Mercury to the Sun varies from about 27 million miles at its closest, to about 41 million miles at its furthest.
Mercury races around the Sun faster than any other planet. A Mercurian year (the time it takes for the planet to go once around the Sun, is only 88 days, while our year on Earth is 365 days. Mercury does not spin as fast as Earth, though, so a Mercurian day (the time it takes a planet to rotate once) is 59 Earth days!

Can I See It?
Yes you can, and you won't need a telescope, but Mercury is normally visible for a few days only three or four times a year. Because of its closeness to the Sun, Mercury is normally hidden by sunlight. When the planet is visible, you either have to get up before sunrise or be watching closely just after sunset. Mercury never gets very far above the horizon, so you will also need a place where can see clearly to either the east or west. Check the sky maps here at Astronomy for Kids. If Mercury is going to be visible, we will tell you when and how to see it.

How Big Is It?
Mercury is the second smallest planet in the solar system. Pluto is the only planet that is smaller. Earth is about 7,200 miles in diameter, while tiny Mercury is less than half that size at about 3,000 miles in diameter. Put another way, if Earth was the size of a baseball, Mercury would be a little smaller than a ping-pong ball. Mercury is so small that Ganymede, one of Jupiter's moons, and Titan, one of Saturn's moons, are both larger.

How Did It Get Its Name?
Mercury is named for the Roman god of commerce and thievery. It may have gotten this name because of the way it quickly appears and disappears from our view.

What Is It Made Of?
Mercury is one of the rocky planets of the solar system, along with Earth and Venus. Mercury is made up mostly of iron, with a thin rocky layer on the planet surface.

What's It Like on The Surface?
On thje surface of Mercury, you will see that there are many craters on its surface. The planet has been hit many, many times through the years by asteroids and other objects. These impacts are responsible for all the craters on the surface. Earth probably had this many craters at one time, but our weather has worn the down over the years.
The weather on Mercury varies from extremely hot to extremely cold. If you were on the side of the planet facing towards the Sun, you would quickly melt, as the temperature would be around 700 degrees! The "daytime" temperature on Mercury varies, depending on how close it is to the Sun. At the other extreme, the temperature on the "nighttime" side of the planet (the side away from the Sun) can be over 300 degrees below zero! Mercury is not a very pleasant place. 



Venus is the second planet from the Sun, located in between Mercury and Earth. The orbit, or path, Venus follows around the Sun is nearly circular, so the planet's distance from the Sun averages about 65 million miles. Being closer to the Sun, a Venusian year, the time it takes for it to complete a trip around the Sun, is just 225 days. Venus spins more slowly than Earth, though, so a day on Venus, the time it takes for the planet to turn once, is 243 days, which means that a day on Venus is longer than it's year! Even more strange is the fact that Venus rotates from East to West, which is just the opposite of Earth and most of the other planets.

Can I See It?
Yes, you can see Venus for several months each year, either in the morning or evening sky, and you don't need a telescope. Venus is called both the morning and evening star, and ancient astronomers thought it was two different objects. When it is visible, Venus is the second-brightest object in the sky, being outshone only by the Moon. You would never guess that something that is so beautiful could be so unpleasant in reality (see What's It Like on the Surface below). Since Venus is closer to the Sun than we are here on Earth, you could see the planet going through phases like our Moon does if you have a telescope.
Be sure to check to sky maps here at Astronomy for Kids. If Venus is going to be visible during a month, we will tell you where and when to see it.

How Big Is It?
Venus is almost the same size as Earth, with a diameter of a little over 7200 miles. This is, thankfully, the only way that Venus is similar to Earth.

How Did It Get Its Name?
Venus was named for the goddess of love and beauty. This is definitely a case of beauty being only skin deep, as Venus is a very unpleasant place, with winds that blow hundreds of miles an hour, and temperatures that are hot enough to melt most metals!

What Is It Made Of?
Venus is one of the solar system's rocky planets, along with Earth and Mercury. The planet has an iron core, which is covered by a rocky layer. This rocky layer has a lot of lava, which has been generated by the many volcanoes on its surface.

What's It Like on The Surface?
To put it mildly, Venus is an extremely unpleasant place. The bright white light that we see from Earth is a result of sunlight being reflected off the clouds that completely cover the planets surface. These clouds are made of sulfuric acid, which is an extremely dangerous substance. When you get to the planet's surface, things get even worse. The temperature on Venus averages around 900 degrees Fahrenheit, which is hot enough to melt lead! That's not all, the clouds on Venus have created at atmosphere that is the same as being half a mile underwater here on Earth. The air pressure would be enough to crush some submarines. Finally the winds on Venus are almost always faster than a tornado, averaging around 240 miles per hour!
The few spacecraft that have managed to land on Venus have lasted less than an hour before the heat and air pressure have melted and crushed them.
For this reason, a lot of what we know about the surface of Venus has come from spacecraft that have studied the planet from a safe distance. We have also been able to map some of the planet's surface using radar telescopes here on Earth. What we have found is that Venus has a surface that has many mountains (some higher than Mount Everest), volcanoes and plains filled with lava.