essentials to life a description of factors that have allowed complex life to evolve on earth as...
TRANSCRIPT
Essentials to LifeA 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 LocationThe most far reaching galaxies are too old to support life
Metals and other heavier elements were not created yet
Type of GalaxyMost types of galaxies such as small , elliptical, and clustered ones are metal-poor and could not support the formation of Earth
Solar System LocationToo close to the center – too populated
Too many “energetic processes”
Too far away – stars are metal-poor
Planet LocationToo close, water would evaporate, tidal lock too far away, too cold!
Size DOES MatterSun
Appropriate lifetime (too short, life couldn’t develop)
Energy produced / given off is not highly rich in UV rays
EarthToo 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
Having the Right Neighbors
MoonStabilizes tilt
Not too close to create chaotic tides
JupiterNot too close to disrupt orbit
Close enough to attract all comets / meteors / asteroids
Earthly FeaturesOceans
Not too much or too little (anyone seen Waterworld?)
Plate Tectonics / Internal HeatRenews land nutrients
Molten core creates magnetic field
Supports biological diversity
AtmosphereEnough carbon but not too much for runaway greenhouse effect (Venus)
Appropriate temperatures (thanks to distance)
Appropriate composition, pressure
Oxygen, photosynthesis
Few global catastrophes
What Life NeedsCarbon and other life building block elements
Water on / near surface
Appropriate atmosphere
Long period of stability
Abundance of heavy elements at core, crustFe, Mg, Si, O – earth structure
U, Th, K – radioactive heat
C, O, N, H, P – biogenic building blocks
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
Looking for Signs of Life
Type of galaxy , location within the galaxyInner – 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