AST 180: Lecture 24
The Search for Extraterrestrial Life
Reading: Chapter 18
Life Depends on Chemistry
  • Carbon is one of only 5 elements that can bond with three or more other elements
  • The others are Boron, Nitrogen, Silicaon, and Phosphorus.
  • Only Carbon builds flexible and strong bonds that allow the formation of very large, complex, and diverse molecules needed by life.
  • Organic Chemistry is the study of carbon compounds
  • Complex Carbon compounds occur in interstellar space
  • Abundant organic molecules are found in comets
  • Organic molecules are also found in carbonaceous chondrites.
The Miller-Urey Experiment created the Precursors of Biomolecules
  • Stanley Miller and Harold Urey simulated conditions in the early Earth atmosphere
    • Hydrogen, Ammonia, Methane and Water Vapor mixed in a closed container
    • Electric Charge used to simulate lightening
    • Results cycled through boiling water w/residue trapped
    • Residue contained Amino Acids - the building blocks of proteins
  • Geochemists now realize that Earth's early atmosphere had more carbon dioxide, nitrogen instead of methane and ammonia.
  • "Miller-Urey synthesis" is not as efficient but still works
  • Remaining Big Unsolved Problem: How do these building block molecules get linked together to form Protein, DNA, etc.
Could Life Exist Elsewhere?
  • Life Exists in an Extreme Range of Terrestrial environments
  • It has even survived three years On the Moon
  • Similar environments exist in the solar system or have existed in the past (on Mars or on Europa
  • Similar enivironments may exist on planets in Habitable Zones around other stars.
  • Its a small needle in a big haystack!
    • Where to listen?
    • On What Channel?
  • The "Water Hole" is a region in "frequency" that might be targeted
The "Drake Equation" estimates the likelihood of hearing from ET
  • It provides terms which are the target of study in NASA's Astrobiology program
  • How many habitable planets are there?
  • How often does life arise in a suitable environment
  • How often does life evolve to produce a technologically capable civilization
  • How long do technologically capable civilizations last?
    Life in the Universe will be explored next Fall in a NEW COURSE:
    AST 183 and AST 184L
    AST 184L will include weekend field trips to Grand Canyon, Grand Staircase-Escalante National Monument and Meteor Crater. It will be FUN! Tell your friends!