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Habitable Planets.docx

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Department
Life Sciences
Course
LIFESCI 2H03
Professor
Luc Bernier
Semester
Winter

Description
Habitable Planets: Only earth? - Until now the only example of a known habitable planet - Earth orbits the sun within a regions … - Region where an earth analog planet can maintain liquid water on tis surface - The atmosphere provides a certain conc. Of greenhouse gases - Has the right mass to regulate plate tectonics Water: - The best solvent for life to emerge and evolve in o Has the ability to form h-bonds with other H2O molecules  This is ideal for proteins - Water is an abundant compound in our galaxy o Clouds and stellar clouds HZ: - The inner edge of the HZ zone, this is where we see runaway greenhouse conditions o All water is found as vapour, no liquid water present  Venus, mercury - The outer edge of the HZ the greenhouse effect fails to keep the planet above the freezing point o The water is frozen and found in the solid form  Neptune, Saturn - The earth is found in the HZ, the conditions are ideal o Distance from the sun is just right o Depending on the mass of the star the HZ might be closed (small star) or further (large star) Main factors: for life: - Long time span o Enough time for evolution to take place, the earth has been relatively stable in recent time - Liquid water in contact with building blocks - Environmental conditions that allow liquid water to exist Atmosphere: - Dense enough that can stabilize the surface temp - Greenhouse effect, caused by compounds that are very efficient absorbers in the infrared o CO2 o CH4 o N2O  These gases have caused our current temp with out them it would be about -16 degrees C Earths Radiation Budget: - The earth receives radiation form the sun - The earth also releases its own radiation (infrared) o Only a small fraction of this energy is actually lost o Most remains on earth Venus: - When the temperatures are exceeding a limit you end up with Venus o Earth may have looked like Venus when it was first forming - Surface pressure 9000 kPa - Surface temperature 480 degrees C - Has an atmosphere but very little water o Not sur
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