Earth Facts

Earth

Viewed from space, planet Earth has blue oceans, white clouds and polar ice caps, and dark areas of land. It is the only planet we know that has life. Life on Earth only thrives because there is a balance between animals, which use up oxygen and release carbon dioxide; and plants, which take in carbon dioxide and produce oxygen. For all life to survive, a steady temperature is important: a few degrees hotter and the ice caps will melt, flooding large areas of land; a few degrees colder and crops will not grow.We need to be very careful not to disturb this delicate balance and turn out living planet into a barren desert such as Mars or Venus.

The Earth's crust contains over 2,000 different minerals. Only about 20 of these minerals are made up of different chemical elements. Just eight elements make up 99% of the Earth's crust.

Area of land: 57,268,900 square miles (148,326,000 km�), equals 29% of the total surface of the Earth.

Area of water: 139,668,500 square miles (361,740,000 km�), equals 71% of the total surface of the Earth.

Deepest ocean trench: Mariana Trench, Pacific Ocean, 36,000 ft (11 km) below sea level.

About a fifth of the Earth's land surface is mountainous and a further eighth is covered in desert.

Earth is the only planet in the Solar System known to have liquid water (although the Moon is now shown to have ice water). Of all the water on Earth, 97% is saltwater. Only 3% is freshwater and two-thirds of this is frozen into ice. Only 1% of all the Earth's water is in lakes, rivers, or underground.

The largest freshwater lake is Lake Superior on the border between Canada and the USA. Its area is 31,800 square miles (82,400 km�). The Caspian Sea is the largest saltwater lake, or inland sea. It is about 144,000 square miles (372,000 km�) in area.

The oxygen in the Earth's atmosphere is produced by plants. About 70% of it comes from tiny plants, called algae, floating in the oceans. Plants also take in the carbon dioxide that animals breathe out.

Mass (kg)	5.98 x 10^24
Diameter (km)	12,756
Mean Density (kg/m^3)	5,520
Escape Velocity (m/sec)	11,200
Average Distance from Sun (AU)	1
Rotation Period (length of day in Earth hours)	23.93
Revolution Period (length of year in Earth days)	365.26
Obliquity (tilt of axis)	23.4�
Orbit Inclination	0
Orbit Eccentricity (deviation from circular)	0.017
Mean Surface Temperature	281�K
Maximum Surface Temperature	310�K
Minimum Surface Temperature	260�K
Visual Geometric Albedo (Reflectivity)	0.39
Highest Point on Surface	Mount Everest (over 8 km above sea-level)
Atmospheric Components	78% Nitrogen, 21% Oxygen, 1% Argon
Surface Materials	Basaltic and Granitic rock and altered materials

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