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Transcript
The Search for Life in the Solar System HNRS 228 w/Geller Reviewing Chapter 6 What’s Up Review Requirements for Life Elements, Energy, Water, etc. Searching for Life in Our Solar System Remote Sensing, Robotics, Human Exploration, etc. Biological Tour of the Solar System Terrestrial Planets, Jovian Planets, other bodies Environment for Life? Source of elements to build cells Source of energy Medium for transporting molecules H2O and CO2 Phase Diagrams (IMPORTANT environmental consideration) Exploring the Solar System Observations from Earth ground or orbit based Robotic spacecraft flybys, orbitals landers Human exploration Planet Generalization Terrestrial planets are closer to sun Mercury Venus Earth Mars Jovian planets furthest from sun Jupiter Saturn Uranus Neptune Planetary Summary Major Constituents Mass (Earth=1) Density (g/cm3) Mercury Venus Earth Mars 0.06 0.82 1.00 0.11 5.4 5.2 5.5 3.9 Jupiter Saturn 318 95 1.3 0.7 H, He H, He Uranus Neptune 14 17 1.3 1.7 Ices, H, He Ices, H, He Planet Rock, Rock, Rock, Rock, Iron Iron Iron Iron Some Conclusions Planets formed at same time as sun Planetary and satellite/ring systems are similar to remnants of dusty disks such as that seen about stars being born (e.g. T Tauri stars) Planet composition dependent upon where it formed in solar system Nebular Condensation Model Most remnant heat from collapse retained near center After sun ignites, remaining dust reaches an equilibrium temperature Different densities of the planets are explained by condensation temperatures Nebular dust temperature increases to center of nebula Nebular Condensation Physics Energy absorbed per unit area from sun = energy emitted as thermal radiator Solar Flux = Lum (Sun) / 4 x distance2 Flux emitted = constant x T4 [Stefan-Boltzmann] Concluding from above yields T = constant / distance0.5 Nebular Condensation Chemistry Molecule H2 H2O CH4 NH3 FeSO4 SiO4 Freezing Point Distance from Center >100 AU 10 K >10 AU 273 K >35 AU 35 K >8 AU 190 K >1 AU 700 K >0.5 AU 1000 K Nebular Condensation Summary Solid Particles collide, stick together, sink toward center Terrestrials -> rocky Jovians -> rocky core + ices + light gases Coolest, most massive collect H and He More collisions -> heating and differentiating of interior Remnants flushed by solar wind Evolution of atmospheres Biological Tour of the Solar System Consider problems posed for life on each of the following Moon Mercury Venus (Mars will be discussed in Chapter 7) Jovian Planets Other Moons Asteroid, comets and other debris Some References The Search for Life (especially in the solar system) http://www.scibridge.sdsu.edu/coursemats/introsci/Solarsys/lecture.html http://www.resa.net/nasa/ocean_hydrothermal.htm http://www.nationalacademies.org/ssb/lifeoriginsmenu.htm http://www.phy.syr.edu/courses/modules/SETI/where.html Books Life on Other Worlds (Dick) Cradle of Life (Schopf) Life Everywhere (Darling) Life on Other Worlds and How to Find It (Clark)
