Planets Habitability PDF

Key points: Temperature influences how quickly atoms and molecules move. Low temperatures cause chemicals to react slowly which interferes with the reactions necessary for life. Too much temperature causes protein and carbohydrate molecules to break apart. It causes evaporation of water. Atmospher...

Key points: Temperature influences how quickly atoms and molecules move. Low temperatures cause chemicals to react slowly which interferes with the reactions necessary for life. Too much temperature causes protein and carbohydrate molecules to break apart. It causes evaporation of water. Atmosphere is our protective shield. It traps heat, shields the surface from harmful radiation, and provides chemicals needed for life, such as nitrogen and carbon dioxide. Small planets and moons have insufficient gravity to hold an atmosphere. The gas molecules escape to space, leaving the planet or moon without an insulating blanket. Too much atmosphere makes the surface too hot for life. Energy is used by organisms to run life processes. When there is too little or too much sunlight, organisms die. Although, too many energy rich chemicals is not a problem. Nutrients are important to build and maintain an organism’s body. Planets without systems to deliver nutrients to its organisms cannot support life. Too active circulation systems, such as the constant volcanism on Jupiter’s moon or the churning atmospheres of the gas planets, interferes with an organism’s ability to get enough nutrients. EARTH SYSTEM is our planetary environment that relies on the interactions among a vast combination of factors that enable it to support life. Atmosphere The atmosphere is the thin gaseous layer that envelops the lithosphere. One of the most important processes by which the heat on the Earth's surface is redistributed is through atmospheric circulation. Hydrosphere is the total amount of water on a planet. About 70% of the Earth is covered with liquid water and much of it is in the form of ocean water Only 3% of Earth's water is fresh: two-thirds are in the form of ice, and the remaining one-third is present in streams, lakes, and groundwater Lithosphere This sphere includes all the stuff that make up the crust and the core of the earth. It includes everything natural and lifeless that make up the surface of the earth. The Biosphere is the set of all life forms on Earth. It covers all ecosystems Ecosystem-biological community interacting with each other For the majority of life on Earth, the base of the food chain comprises photosynthetic organisms. During photosynthesis, CO 2 is sequestered from the atmosphere, while oxygen is released as a byproduct. The biosphere is a CO2 sink, and therefore, an important part of the carbon cycle. The four spheres can be and often are present in a single location. Although the four systems have their individual identities, there is important interaction between them.