Solar System Nebular Hypothesis Nebular Hypothesis Solar System was produced by the gravitational collapse of a gas cloud the remnant of a supernova explosion Concentration of heavy elements in inner ID: 571985
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GY111 Physical Geology
Solar SystemSlide2
Nebular Hypothesis
Nebular Hypothesis: Solar System was produced by the gravitational collapse of a gas cloud – the remnant of a supernova explosion.
Concentration of heavy elements in inner planets.Most of the mass of the Solar System is composed of H and He atoms.Slide3
Planets of the Solar System
Inner (Terrestrial) Planets: Mercury, Venus, Earth, Mars.
Outer (Jovian) Planets: Jupiter, Saturn, Uranus, Neptune.Pluto: former moon of Neptune.Asteroid belts: shattered remains of a proto-planet.Slide4
Inner (Terrestrial) Planet Characteristics
Metallic Core and rocky (silicate) mantle/crust.
Thin atmospheres because of proximity to Sun.Very small moons because of low gravitational attraction (Earth being a notable exception).Asteroid belt probably represents a failed planet formation from early in the Hadean Eon.Density is high – averaging approximately 5.0.Slide5
Outer (Jovian) Planet Characteristics
Thick gaseous atmospheres dwarf a small metallic/silicate core/mantle/crust.
Atmospheric gas is retained because of distance from the sun.Intense gravitational fields can capture large comets or planets. This protects the inner planets from impacts.Overall density is low – Saturn has a density < 1.0.Slide6
Earth’s Early HistorySlide7
Early Impactor Hypothesis
Mars-sized (33% mass of Earth) impactor collided during the Hadean.
Isotopic signatures on Earth and Moon are very similar.Earth’s gravity would not have been able to capture a mass as large (25% of Earth) as our moon.The melting event triggered by the impact allowed Earth to differentiate into Crust, Mantle, and Core.Slide8
Differentiated Earth
Fe-rich core.
Silicate mantle and crust.Differentiation makes possible plate tectonics and the magnetic field of the Earth.Slide9
Earth’s Early Atmosphere
Volcanic outgassing formed Earth’s early atmosphere and hydrosphere (H, N, CO
2, H2O).Comet impacts also added gases and water.Note that the early atmosphere lacked oxygen (O2).Slide10
Early Bombardment Period
Haden Eon marked by bombardment of asteroids and comets.
Evolution of life was impossible until heavy bombardment ceased.The cratered surface of the moon best records the Late Heavy Bombardment Period.Slide11
Significant Solar System Events Through TimeSlide12
Earth/Venus Tectonics ComparisonSlide13
Mars Topography
Mars has more extreme topographic relief because of the lack of water erosion.
Olympus Mons: largest known volcano in the solar system (elev.=22 km; 14 miles).Slide14
Mars Exploration
Mars rovers have provided a wealth of data about the planet.
Mars resembles Earth more than any other planet.Slide15
Evidence of a “Wet” Early Mars History
Stream-cut channels dissect the topography.
Stratified and cross-bedded sediments.Evaporite deposits.Slide16
Mars Lake Beds
Precipitation of Hematite from evaporating lake.
Laterally continuous stratified beds.Evaporite deposits of Halite and Gypsum.Slide17
Exam Summary
Know difference between inner and outer planets.
Be familiar with the Impactor hypothesis for the origin of the moon.Know the lines of evidence that point to the past presence of liquid water on Mars.Know why Olympus Mons is the largest volcano in the solar system .Know about the origin and early composition of Earth’s atmosphere.