LIFE ON EARTH
Life on earth is possible because of a coincidental combination of factors: The habitable zone: Earth is at the right distance from the sun to have liquid water on its surface, and for the atmosphere to be at a reasonable temperature for life to occur. It also doesn't stray too far from the optimal distance, making the temperature stable. Stable planet: We aren't inundated with lava every day. This gives life the chance to happen without being destroyed instantly. Water: We have it. Necessary for life. Atmospheric composition: Began with plenty of carbon oxides and simple organic compounds with very little free oxygen.