The planet Mercury is the closest of the planets to the Sun. Because this planet lies so close to the Sun, and as a result somewhat near to Earth, it is visible to observers on Earth in the late evening or early morning sky. Because of this, Mercury has become a part of the mythology and legend of almost every culture throughout the history of the Earth.
This planet is often called a morning star. This is because Mercury shines brightly in the early morning just before the sun rises. It has also been called an evening star for the same reason. Mercury is often visible for a brief period of time just after the Sun sets.
Mercury Has No Atmosphere The planet Mercury is too small and has too little gravity to hold onto an atmosphere. Any gases released from the planet quickly escape into space. Also, Mercury is so close to the Sun that any atmosphere is quickly blown away by the Sun's solar winds. That means that there is almost no air on Mercury.
|Venus: Earth's Twin|
|Venus is called the Evening Star. It is called this because it looks so bright to us from Earth.|
Venus and Earth are almost the same size. Venus is the closest planet to Earth, but it does not have oceans or human life like Earth. Venus gets so hot during the day that it could melt a lead cannonball. The temperature rises to 484 degrees Celsius on the side facing the Sun. Venus has very thick, rapidly spinning clouds which cover its surface. These clouds hold heat in. That is why Venus gets so hot. These clouds also reflect sunlight. That is why Venus appears so bright to us here on Earth. There are constant thunderstorms in these clouds. Venus has several large inactive volcanoes. Much of the surface is covered by old lava flows from these volcanoes.
Venus is unusual because it rotates in a direction opposite that of all of the other planets. Venus spins very slowly as it orbits the Sun
|Earth: The Water Planet|
|Seventy percent of the Earth's surface is covered by water. The remaining 30 percent is covered by mountains, volcanoes, deserts, plains, and valleys.|
Earth is the third closest planet to the Sun. It has an atmosphere
made up of many different gases, but
mainly it is nitrogen and oxygen. The atmosphere gives us air to breathe. We
live on the planet Earth.
The Earth orbits around the Sun. It takes one year to go around the Sun one complete time. The Earth also rotates, or spins, on its axis. It takes one day to spin around one complete time. The Earth's axis is not straight up and down, but tilted a little bit. This tilt is responsible for us having seasons. Otherwise, the temperature would be pretty much the same all year long.
|Mars: The Red Planet|
|Some of the meteorites found on Earth are actually pieces of the planet Mars. As of June 2006, thirty-four "Martian meteorites" have been found.|
The temperature on Mars can be very, very cold. On its warmest day, Mars can
still be a very cold place. At the top and bottom of the planet are poles just
like on Earth. During the Martian winter, ice caps can be seen at the poles.
Mars has many craters which were formed by meteorites or asteroids hitting it. Mars also has some of the tallest volcanoes and some of the deepest valleys in our solar system. Mars has two moons, Phobos and Deimos which have unusual shapes. Scientists think these potato-shaped moons were once asteroids captured by Mars' gravitational pull .