Nebular Hypothesis and Origin of Earth s Water

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Cody Hector Wells
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Sun in the middle. C. Planar ellipse (oval), though nearly circular Top view Edge view Consider H 2 O and the planets.

1 Nebular Hypothesis and Origin of Earth s Water What is the shape of our solar system? A. Spherical: the Sun is in the center, the planets orbit in spherical shells. B. Disc shaped: fat in the center, tapering to planar at the edges. Sun in the middle. C. Planar ellipse (oval), though nearly circular Top view Edge view Consider H 2 O and the planets. Which of the following is correct? A. Earth is the only planet with H 2 O on the surface. B. Most of Earth s H 2 O is in the oceans. C. H 2 O was not originally present in the Earth and was added to the Earth early in it s history. 1

Big Bang Theory From work of Einstein and Hubble ~14 Ga All matter in one point Exploded Expanding still

Stars and planets form from nebulae - the Nebular Hypothesis.

Hypothesis: Clouds of gas/matter contract under the force of gravity.

2 Big Bang Theory From work of Einstein and Hubble ~14 Ga All matter in one point Exploded Expanding still Matter is concentrated in clouds called nebulae. Stars and planets form from nebulae - the Nebular Hypothesis. Food for thought Nebular Hypothesis: formation of solar systems Horse Head Nebula Crab Nebula Nebular Hypothesis: Clouds of gas/matter contract under the force of gravity. Gasses (mostly H and He) compress into dense balls = Star Heat by compression to > 1x106 K Fuse heavier elements (heat generated from nuclear reactions) Emit light and HEAT Supernova = exploded star, expels heavy elements forming a new Nebula Repeat process 2

3 Nebular Hypothesis Look at the shape of these galaxies, they show the effects of rotation. Now, lets draw the nebular hypothesis and formation of our solar system. First, watch this: 3

Relationships between planets: Why are Inner Planets lower in mass than outer planets? A. They have greater density B. They formed in a region where the solar wind was strong. C.

4 Relationships between planets: Why are Inner Planets lower in mass than outer planets? A. They have greater density B. They formed in a region where the solar wind was strong. C. They formed in a region where temperatures were cold. Relationships between planets: Why are Outer Planets lower in density than inner planets? A. They have greater mass B. They formed in a region where the solar wind was strong. C. They formed in a region where temperatures were cold. Problem:Where does all the water come from? Water (H2O) is volatile and thus would not be present during accretion of terrestrial planets (i.e. Earth) 4

Where does Earth s water come from? 1. Original Water: Hydroxyl (OH) groups in minerals that compose the meteorites that accreted late during formation of the Earth.

More complex than addition of water by comet and meteorite impacts Earth didn t have oceans 4.55 b.y. ago So, where did surface water come from?

5 Where does Earth s water come from? 1. Original Water: Hydroxyl (OH) groups in minerals that compose the meteorites that accreted late during formation of the Earth. (initially, volatile depleted planetesimals). 2. Added Water: Post accretion, water was added by the impact of comets (H 2 O) and meteorites (OH). What about Oceans? Where do they come from? More complex than addition of water by comet and meteorite impacts Earth didn t have oceans 4.55 b.y. ago So, where did surface water come from? It came from Earth s interior and was released during mantle melting (seafloor spreading). Releasing of Earth s internal water to form oceans Planetesimals collide to build Earth This adds original water (comet and meteorite impacts Also, the collisions and compression (and nuclear decay) heat the early Earth to the point where it s outer portion melts. This is called the Magma Ocean Stage. During this melting, Earth s current structure develops (core, mantle, crust) After Earth cools a bit, Plate Tectonics begins and The mantle degasses Liberates mantle water to surface during seafloor spreading This forms the Oceans and Atmosphere! 5

Closer look at Magma Ocean stage and development of Earth s Structure and formation of the Moon Let s draw a better picture What is the shape of our solar system?

6 Closer look at Magma Ocean stage and development of Earth s Structure and formation of the Moon Let s draw a better picture What is the shape of our solar system? Spherical: the Sun is in the center, the planets orbit in spherical shells. Disc shaped: fat in the center, tapering to planar at the edges. Sun in the middle. A. Planar ellipse (oval), though nearly circular Top view Edge view 6

Review questions 1. 2. 3. How does temperature vary across the solar system? How does planet size and density change with distance from the sun?

7 Consider H2O and the planets. Which of the following is correct? A. Earth is the only planet with H2O on the surface B. Most of Earth s water is in the oceans C. H2O was not originally present in the Earth and was added to the Earth early in it s history. Review questions How does temperature vary across the solar system? How does planet size and density change with distance from the sun? What caused the variation in planet size and density? Review questions How did the Moon form? How does the Moon differ from the Earth (size, mass, density, structure)? When did the moon form? 7

8 Review questions 1. What is the source of Earth s water? 2. Where did the water in Earth s oceans come from? 3. How long have oceans existed on Earth? 8

Nebular Hypothesis and Origin of Earth s Water

Nebular Hypothesis and Origin of Earth s Water What is the shape of our solar system? A. Spherical: the Sun is in the center, the planets orbit in spherical shells. B. Disc shaped: fat in the center, tapering