The planet we all know and love! Actually, there is still much more things that we have to learn about earth that scientists still have yet to discover. Earth, as seen from satellite images is a beautiful, bright blue planet filled with patches of white water vapor (clouds) that cover about 40% of the earth.

Unlike all other planets, earth actually supports life. Well , it is uncertain whether any of the planets in this solar system has living organisms or used to have.

Scientists theorize that earth was formed 4.5 billion years ago when many other planets formed. As most people should know, earth takes 365 days to orbit the sun and completes one rotation in 24 hours. Earth's orbit is somewhat elliptical with only a 3% difference from a circular orbit. It is known that the tilt of the earth\rquote s axis is 23.5 degrees, which accounts for the seasons on earth. The tilt causes certain parts of the planet to be heated differently thus causing seasonal changes.

	This image wasl taken by the Solid State Imager (SSI) on Galileo during its first flyby of the Earth in December of 1990. This is a view of the South Atlantic Ocean
	When this image was taken several hours after Galileo's Earth flyby on December 8, 1990, the spacecraft was about 200,000 kilometers (124,000 miles) from Earth. Surrounding the icy continent, the dark blue of three oceans may be seen: the Pacific to the lower right, the Indian to the upper right, and a small section of the Atlantic at the upper left.
	This is a view of Austrailia as seen by the SSI on Galileo's flyby of Earth in December 1990.

Of all the inner planets (Mercury, Venus, Earth, and Mars), Earth is the only one that contains water in its liquid form. This is essential to the development of life on Ear th, as scientists believe. Since water was so important for life, scientist today use liquid water as one of the main references to finding life on other planets inside and out of this solar system.

Earth has an atmosphere made up of nitrogen, carbon dioxide, hydrogen, oxygen and water vapor. Earth's atmosphere consists of four layers, the troposphere, Stratosphere, the mesosphere and the thermosphere. The ozone layer, which consists of three molecules of oxygen molecules bonded together. This layer helps to protect earth from dangerous radiation and reflects most of the radiation from entering earth. The ozone layer is approximately 10 miles up from the ground.

Earth has an inner core of solid nickel and iron and a layer of liquid iron and ni ckel surrounds this core. Another layer called the mantle covers this layer of liquid metal. The lower mantle is made up of the minerals pyroxene, olivine, and garnet. The upper mantle called the asthenosphere is also similar to the lower mantle. The surface, called the lithosphere, or crust, is where the continents and the bottom the oceans lay.

This is a picture of Lake Victoria, as taken by the Clementine Spacecraft

The large, bright, sometimes round object that we see in the sky every night is not an alien craft. It is the Moon! The Moonis Earth's natural satellite. The Moon orbits Earth approximately 221,000 miles(356,000 km) away at its closest point, and 253,000 miles (407,000 km) away at its farthest point and travels over 22,870 miles per hour(36,800 km/hr).

The Moon, unlike the Earth, has no atmosphere and has a weaker gravitational force because its mass is only about 1% of Earth's mass. The Moon, because it has no atmosphere, has a greater range of temperatures, on its surface.it can be below-300°F (-184°C) at night and 214°F (184°C) at midday.

If an observer takes a good telescope or powerful binoculars, he or she can see that the moon is covered with impact craters. There are also darker areas and lighter areas that can be seen with the naked eye. The darker areas on the moon are called Maria and are younger because they have less impact craters. The lighter areas are called terrae and are higher than the Maria.

The moon has been mapped and thoroughly explored by spacecraft launched from Earth. American astronauts also landed on the moon in the Apollo 11 mission. A series of 12 Americans actually landed on the moon and they managed to collect about 381 kg or 670lbs of moon rock and brought them back to earth. The Clementine spacecraft, on its way to Jupiter managed to map the entire surface of the moon in February 1994.

	These images of the Moon are a selection of images taken by the Clementine spacecraft. The first image is a mosaic of the near side of the moon as taken by the star trackers. The images were taken on March 15, 1994. In this view, north is up. The bright crater near the bottom of the image is the Tycho.
	Color ratio image of Tycho as seen from the spacecraft Clementime
	Image of the Earth over the lunar horizon from Clementine. This image was taken by Clementine as it came over the north lunar pole at the completion of mapping orbit 102 on March 13, 1994. The angular separation between lunar horizon and Earth has been reduced for illustration purposes. The large crater at the bottom of the image is Plaskett (180 W longitude, 82 N latitude).