When the highly successful Pioneer spacecraft finished its examination of Jupiter, it was catapulted toward the outer reaches of our solar system. As the spacecraft aimed its instruments at Earth, only enough light reached it to produce one pixel of color. The pale blue dot produced was an image of Earth from billions of miles away. This illustrates the vastness of space which surrounds our planet. We are truly on an island surrounded by a sea of the hostile conditions of our solar system.

There are many factors which have allowed our pale blue dot to support a biosphere. Our location in the solar system (distance from the sun) is partially responsible for allowing liquid water to exist at the surface. The Greenhouse Effect is also responsible. Our comparatively large moon has a stabilizing effect on Earth's rotation so that there are not drastic seasonal fluctuations. More specifically, our moon minimizes the amount of tilt Earth experiences over great periods of time. Also, the presence of giant planets such as Jupiter can help to absorb impacts of comets and asteroids.

Even though life is very robust on Earth, it is also very sensitive to slight changes in temperature, pressure, radiation, nutrition, and water content. The interrelationships between all of these factors help to define Earth's biogeochemical cycles. These help regulate the extremes within our life-supporting atmosphere. Each cycle involves particular elements that are essential in biospheric, atmospheric, and geologic processes. Examples include the oxygen, carbon, and nitrogen cycles. Studying a specific cycle usually involves tracing an element through biotic and abiotic reservoirs--places where the element is stored. Although we can talk about them individually, they are all interdependent. For example, photosynthesis is a primary way in which carbon is taken out of the atmosphere (from CO2) and fixed into plant and bacterial mass. This process also liberates the oxygen that is stored in other chemical compounds. Just the same, when we breathe (respire) we are pulling free oxygen out of the air and releasing CO2. Some of the carbon in your body might have been part of a plant at one time, or even might have been bound in the chemical structure of a rock!

We owe a great deal to our pale blue dot and the protection that it provides for humanity. But even beyond the vastness and complexity of our solar system, our home planet itself is an intricate system. Our environment is ever-changing and it is not always easy for scientists to predict the outcome of these changes. Even though our atmosphere has varied a great deal through Earth's history, it has allowed life to thrive for at least 3.8 billion years. By studying the components of the Earth system, we will be better able to make decisions about environmental issues. With that in mind, read on to learn more about Our Changing Planet.