Is There Life Beyond Earth? Section 6

How many intelligent alien civilizations do you think exist? Drake equation-an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact N = N* fp ne fl fi fc fL The equation can really be looked at as a number of questions

N = N* fp ne fl fi fc fL N, the number of communicating civilizations in the galaxy. N* represents the number of stars in the Milky Way Galaxy fp is the fraction of stars that have planets around them ne is the number of planets per star that are capable of sustaining life fl is the fraction of planets in ne where life evolves fi is the fraction of fl where intelligent life evolves fc is the fraction of fi that communicate fL is fraction of the planet's life during which the communicating civilizations live

Try the Drake Equation Yourself pics/SETI/drake_equation.htmlhttp:// pics/SETI/drake_equation.html What was the number of communicating civilizations in the galaxy that your class came up with? ___________

Exoplanets Exploring Outside of our Solar System (2 clips) –Exoplanets

SETI Program SETI — the Search for Extraterrestrial Intelligence The Mission of the SETI Institute is to explore, understand and explain the origin, nature and prevalence of life in the universe. –Earth Science: The Universe Clip: Searching for Extraterrestrial Life (3min)

Why Complex Life May Be Rare The Rare Earth Hypothesis argues that life on Earth required an improbable combination of astrophysical and geological events and circumstances. Some conditions that a planet needs for complex life to exist –Habitable zone the necessary existence of liquid water requires that the temperature of the planet be neither too high nor too low. –A central star of the right character –Planetary system: Inner and Outer Planets Need a large Jupiter-sized planet to keep asteroids away –Size of planet -if its mass is too large, the planet will become a gaseous planet with an atmosphere made essentially of hydrogen and helium. In such conditions, the chemical reactions of life cannot occur. If it is too small, it will not be able to maintains an atmosphere. –Large moon- keeps the climate stable. –Chemistry of the atmosphere

Life on Earth All living things: Are made up of one or more cells Take in energy and use it to grow and develop Reproduce Give off waste

The “Goldilocks” Conditions Life exists on Earth…No one knows whether life exists anywhere other than Earth. Earth has: –Liquid water –Suitable temperature range –Atmosphere for living things to survive Scientists call these favorable conditions the “Goldilocks” conditions

Extreme Conditions Scientists have discovered living things in places where it was once believed that life could not exist. Examples: Giant tubeworms in the deep ocean Single-celled organisms in hot springs Tiny life-forms inside solid rock

These discoveries show that the range of conditions in which life can exist is much greater than scientists once thought. We have found organisms that can survive in conditions without water, in extreme heat, extreme cold, and extreme acidity

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Life on Mars? Spacecraft have found regions on the surface of Mars that look like streambeds with crisscrossing paths of water Life requires water so scientists hypothesize that Mars may have once had conditions for life to exist

Video clips minutes/main shtml (entire segment- 10minutes) minutes/main shtml Inner Solar System: Mars Clips (5 min total): –Mars Global Surveyor Explores Evidence of Water on Mars –Mars Odyssey Searches for Water and Ice –2003: Mars Express, Beagle II, Spirit Rover, and Opportunity Lander

Life on Europa? One of Jupiter’s moons explored by Voyager spacecraft Europa has a smooth, icy crust with giant cracks Similar patterns occur in the ice crust over Earth’s Arctic Ocean Scientists hypothesize that there is a liquid ocean under Europa’s ice-the water could be kept liquid by heat coming from inside Europa

Water on Saturn’s Moon? Images from NASA’s Cassini spacecraft indicate that one of Saturn’s moons, Enceladus, may contain pockets of liquid water below its icy crust.

Water on Saturn’s Moon Liquid water geyers make Enceladus a very exciting place to look for life. Unknown heat sources inside Enceladus melt ice into deposits of subsurface water and under pressure, these water pockets burst through the icy crust. The white streaks in this image are backlit geysers of water ice, rising hundreds of miles into space from Enceladus’s dark disc

Most Recent Discovery: Water Ice on the Moon In 2009, a NASA probe on India’s lunar orbiter discovered 600 million metric tons (158 billion gallons) of water ice in 40 craters at the Moon’s North Pole. In 2009, NASA crashed two probes into the Moon’s South Pole and there was significant amounts of water in the debris cloud.