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Essentials to Life

Essentials to Life. A description of factors that have allowed complex life to evolve on Earth as noted in Rare Earth: Why Complex Life is Uncommon in the Universe. Location, Location, Location. Galactic Location The most far reaching galaxies are too old to support life

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Essentials to Life

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  1. Essentials to Life A description of factors that have allowed complex life to evolve on Earth as noted in Rare Earth: Why Complex Life is Uncommon in the Universe

  2. Location, Location, Location • Galactic Location • The most far reaching galaxies are too old to support life • Metals and other heavier elements were not created yet • Type of Galaxy • Most types of galaxies such as small , elliptical, and clustered ones are metal-poor and could not support the formation of Earth • Solar System Location • Too close to the center – too populated • Too many “energetic processes” • Too far away – stars are metal-poor • Planet Location • Too close, water would evaporate, tidal lock too far away, too cold!

  3. Size DOES Matter • Sun • Appropriate lifetime (too short, life couldn’t develop) • Energy produced / given off is not highly rich in UV rays • Earth • Too small – internal heat would escape faster • Thin atmosphere, particles would not be gravitationally bound (ex. Mars) • Oceans would also not remain if small • Appropriate tilt size to prevent wild seasonal change in climate

  4. Having the Right Neighbors • Moon • Stabilizes tilt • Not too close to create chaotic tides • Jupiter • Not too close to disrupt orbit • Close enough to attract all comets / meteors / asteroids

  5. Earthly Features • Oceans • Not too much or too little (anyone seen Waterworld?) • Plate Tectonics / Internal Heat • Renews land nutrients • Molten core creates magnetic field • Supports biological diversity • Atmosphere • Enough carbon but not too much for runaway greenhouse effect (Venus) • Appropriate temperatures (thanks to distance) • Appropriate composition, pressure • Oxygen, photosynthesis • Few global catastrophes

  6. What Life Needs • Carbon and other life building block elements • Water on / near surface • Appropriate atmosphere • Long period of stability • Abundance of heavy elements at core, crust • Fe, Mg, Si, O – earth structure • U, Th, K – radioactive heat • C, O, N, H, P – biogenic building blocks

  7. What Allowed this to Develop? • Molten surface • Distance from sun • Galactic location • Development of plant life – photosynthesis • T-tauri phase • Size of planet • 2nd generation star • Luck

  8. Looking for Signs of Life • Type of galaxy , location within the galaxy • Inner – too busy, black holes • Outer – metal poor • Star / Sun – not too massive or give off too many damaging rays (sun only emits 10% of energy in UV), fluctuations in output are small • Planet within a “habitable zone” (not too far, not too close) • Correct age – too old will be metal poor, too young and perhaps not enough heat? (of galaxy, sun, planet) • Metal content in the planets, presence of Carbon (other life building elements) and WATER

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