| Our Unique Planet Earth
Most of our Universe and Solar System is either too cold, too hot, too dense, too vacuous, too dark, too bright, or not composed of the right elements to support life as we know it. The Earth is unique among the planets of our Solar System in having conditions that have been crucial for the evolution, diversification and sustainability of life for billions of years. These include:
- a hydrosphere with liquid water
- an atmosphere with free oxygen (O2)
- a dynamic geosphere with plate tectonics
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The Arrangement of Planets in our
Solar System |
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1-4:
Small and dense terrestrial or rocky planets:
The terrestrial planets are composed primarily of rock and metal alloys and have relatively high densities, slow rotation, solid surfaces, no rings and few satellites.
5-8:
Giant Jovian or gaseous Planets:
are composed primarily of hydrogen and helium and generally have low densities, rapid rotation, thick atmospheres, rings and lots of satellites.
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