• Final in room B130 Van Vleck 12:25pm May 16
• cumulative
• Homework #7 due next Tuesday
• Observing project due next Tuesday
• Extra credit project due next Friday
• Slight change in syllabus: review starts next lecture
• I will cover general topics Tuesday
• please submit specific questions for Thursday

• Basic ingredient of life
• How they may have formed on Earth
• Could this be unique to us?
• Review: where else may have their been life in the solar system?
• Given the basic ingredient is evolution to higher life inevitable?
• probably only if conditions are just right
• Estimating the number of "Just Right" places
• The Drake Equation
• What are we doing to look for life elsewhere
• Telescopes for direct imaging only a dream
• Search for Extra Terrestrial Intelligence (SETI)
• Look for radio broadcast from other civilizations
• You can participate too!
• Social, political, religious ramifications

• Chemically, life as we know it depends on organic molecules
• organic molecules contain carbon (by definition)
• also have hydrogen, nitrogen, oxygen, sulfur, among others
• Review: were these elements common or rare on the proto-planet Earth?
• common
• Where did these elements originally come from?
• Star barf (Supernova explosions)

• Method one: they fell from the sky
• recall different types of meteorites:
• Stony
• Stony Iron
• Iron
• Carbonaceous Chondrite
• Carbonaceous Chondrites contain organic molecules!
• Method two: lightening in an atmosphere of water, carbon dioxide, nitrogen, and hydrogen

• Since Carbonaceous Chondrite meteorites fell everywhere in our solar system, the building blocks of life are everywere
• Are their organic molecules elsewhere in the Galaxy?
• YES!
• Star barf (Supernova explosions) not unique, probably make Carbonaceous Chondrites elsewhere
• Radio astronomers detect emission from other organics
• coming from star forming regions called molecular clouds
• ethyl alcohol, formaldehyde, cyanoacetelete

• Mars: Martian meteorite shows possible fossilized microbes
• Europa: May have warm sub-surface ocean
• Europa is a moon of what planet?
• Jupiter

• NO
• Any hostile environment can squelch life
• Life seems to like liquid water, nice neutral chemical medium for reactions
• Liquid water needs something pressing down on it
• Atmosphere or ice-top
• Planets with no atmosphere like Mercury unlikely to have life
• Sulfur dioxide on Io might be poisonous
• Io is a moon of what planet?
• Jupiter
• Sulfuric and other nasty acids on Venus
• Many ways to keep organic compounds from becoming life
• For life to evolve from organic chemicals, conditions probably have to be just right

• What does it take to be a just right place?
• need a star for warmth, energy
• need a planet to protect from star
• probably need a terrestrial planet
• possibly a particular atmosphere
• stable or unstable conditions to nurture or stimulate life
• Some think land animals got crowded out of oceans
• etc. etc.
• We know a about how many stars form in the Galaxy every year
• from this and other estimates, we can estimate the number of intelligent civilizations in the Galaxy:
• The Drake Equation

• N = number of civilizations (what we are looking for)
• R_s = Rate of Sun-like stars forming in the Galaxy
• f_p = fraction of these stars that have planets
• n_e = average number of Earth like planets in these systems
• f_l = fraction of Earth like planets on which life actually arises
• f_i = fraction of these life forms that that develop into intelligent beings
• f_c = fraction of life forms that develop civilization
• L = lifetime of civilization

• Recall that pluto looks to Hubble Space telescope like Mars did to Percival Lowell
• Will be ever be able to SEE life on other planets?
• only with dream telescopes:
• Planet Imager (probably not possible until 2015)
• would we see canals?  probably not
• More practical search: a spectrum is worth a thousand pictures
• look for spectroscopically evidence of water, oxygen, ozone, carbon dioxide
• Terrestrial Planet Finder possible launch in 2010

Spectrum of simulated planet

• SETI is the Search for Extra-Terrestrial Intelligence
• It is going on right now using conventional radio telescopes
• Listen to radio signals coming from nearby stars
• Analyze for patterns or unusual behavior
• You can be part of this
• coming

• Currently, the radio version of SETI is not funded by the US government
• Depending on the solution to the Drake equation, SETI might be a colossal waste of money
• Mostly collecting noise
• Funds and efforts coming from private individuals and foundations
• On the other hand, new telescopes that discover things about other stars and planets is NASA's usual style
• What if there are other creatures out there?
• Should we be afraid of them?
• What does that mean about Earth-based religions?
• Are they false?

• Basic ingredience of life
• How they may have formed on Earth
• Could this be unique to us?
• Review: where else may have their been life in the solar system?
• Given the basic ingredience is evolution to higher life inevitable?
• probably only if conditions are just right
• Estimating the number of "Just Right" places
• The Drake Equation
• What are we doing to look for life elsewhere
• Telescopes for direct imaging only a dream
• Search for Extra Terrestrial Intelligence (SETI)
• Look for radio broadcast from other civilizations
• You can participate too!
• Social, political, religious ramifications