Life in the Solar System Where have all the Martians gone?
What is Life? • While we can list characteristics of living organisms (and the book does), many non-living systems will exhibit many, if not all, of these characteristics • Is life about reproduction? Is a sterile human alive? • Maybe it's about arising from reproduction? If we took a copy of you by copying all the atoms of your body, would the copy be alive? • The bottom line is:We have no useful definition of life. http://www.lifeinuniverse.org/noflash/Lifedefinition-04-01.html
What do we know? • We don’t know exactly what life is. • We don’t know exactly how life began. • What do we know? • Where does life live? Almost everywhere on Earth. • What are the requirements for life to exist and thrive? • This isn’t too bad. After all, to find life, we first need to know where to look. • Step 1: Decide what life needs and identify the places that meet these requirements so we know where to look.
What is needed for life? • The presence of liquid water • The elements needed for metabolism and reproduction (biogenic elements) • A biologically useful source of energy • Suitable environmental conditions http://www.lifeinuniverse.org/noflash/Conditions-04-02.html
Limiting factor • Biogenic elements (CHONSP…) are all over the Solar System (even in asteroids and meteorites) • Sources of energy: • Sunlight (photosynthesis) • Many chemical reactions generated by heat • Others? • Liquid water requires temperatures of 273-373 K (0-100 C). • Environment • Mainly, no harmful UV rays • Bottom Line: Follow the water http://www.sciam.com/specialissues/0398cosmos/0398jakosky.html
Follow the Water • What planetary bodies have liquid water? • Water needs warmth (273-373 K), so heat is necessary. • Where does heat come from in the Solar System? • Internal heat • Solar heat • Tidal heat • That lead us to… • Earth (duh) • Mars • Europa • http://passporttoknowledge.com/solarsystem/life/water.html
Water on Mars http://mars.jpl.nasa.gov/science/index.html
Missions to Mars • 2001 Mars Odyssey • 2003 Mars Exploration Rovers • 2005 Mars Reconnaissance Orbiter • Beyond 2007 • Smart Lander and Long-range Rover – as early as 2007 • Sample Return – as early as 2011, likely 2014
Missions to Europa? http://www.jpl.nasa.gov/europaorbiter/
Questions • How important will it be if we discovered other life in our Solar System? • How would we know it wasn’t life from Earth? • Is NASA right in concentrating much of its resources on searching for life? (ie., is Europa more important than Io?)