Astronomy Packet: 3
In the last Astronomy Packet we talked about how scientists study the Earth to understand other worlds. They also study worlds which are similar to each other in order to better understand how these worlds work. Comparing different planets to the Earth and to each other is called Comparative Planetology. In Astronomy Packet # 2 we learned about the Moon and Mercury. We used comparative planetology to understand how they are the same and how they are different. This week we are going to explore the following planets: Venus, Earth and Mars.
In order for life as we know it to exist there must be liquid water. Around every star there is a zone where the temperature is just right for water to remain as a liquid. If the planet is too close to the star, it will be too hot and all its water will evaporate. If the planet is too far from the star, then it will be too cold and so all the water will freeze. But if the planet sits just the right distance from its star, then it will be just the right temperature for the water to remain liquid. This life zone is called the Ecosphere.
The Earth sits almost right in the middle of the Sun's Ecosphere, or life zone. But guess what? Venus and Mars also sit in the Ecosphere, but Venus is on the very inner edge, and Mars is on the very outer edge. This is the first thing these three planets have in common. All three are within the Sun's Ecosphere.
What is an Ecosphere?