12. Esker's Theory of Planetary Evolution

Key Points Summarizing the 'Hell, Heaven, and Earth' Series

  1. All the major planets formed out of the same swirling disk of material orbiting the central mass that later became the Sun.

  2. Water ice played a key role in acting as a glue that facilitated the clumping together of the swirling material. This water became trapped within each planet or moon as it continued to grow.

  3. The idea that radioactivity heats the Earth's interior is an ad hoc 'solution' that has no supporting evidence and it has no predicting powers regarding which celestial objects of our solar system should be heated the most. Please put this half-baked idea out with the trash.

  4. Tidal heating is the primary process that heats the interior of the planets and the Galilean moons. This internal heating is what causes these objects to evolve.

  5. The strength of the tidal forces that causes tidal heating are inversely proportional to the distance cube between the two interacting bodies. For this reason, the planets closest to the Sun tend to develop the most internal heating that causes the planet to evolve.

  6. A planet or moon needs to be distorted for tidal heating to occur. This distortion occurs to the rotating Earth as it feels the tidal pull of the Moon, all the rotating planets in general as they feel the tidal pull of the Sun, and the Galilean moons of Jupiter as these moons feel the tidal pull from each other. There is no tidal heating within the Moon because it is in synchronous rotation with the Earth and so it is no longer changing its shape.

  7. Tidal heating is what heats the interior and causes a planet or moon to release the lighter elements and compounds locked in the interior. Once the heat releases these light elements and compounds they are then able to migrate towards the surface.

  8. On reaching the surface these light elements and compounds either escape out to space, join the planet or moon's atmosphere, condensate to form oceans, or solidify to become part of the planet or moon's crust.

  9. Planets and moons can either have no atmosphere, an atmosphere consisting of both light and heavy gas molecules, or an atmosphere consisting of just the heavier gas molecules. Which type of atmosphere a celestial object has is mostly determined by its mass and its atmospheric temperature: the more massive the object and the cooler its surface or atmosphere the more likely it can hold on to an atmosphere. Furthermore, since solar radiation is what heats a celestial body's surface or atmosphere, and solar intensity decreases with increasing distance from the Sun, the largest planets that are the farthest away from the Sun are the most likely to hold on to all of their atmosphere.

  10. As a consequence of tidal heating, not only do planets and moons differentiate but they also shrink. This is because the lightest elements, hydrogen and helium, make up the largest portion of the released material that migrates to the surface, and once these elements are on the surface they escape out to space. The exception to this is the large outer gaseous planets that are still able to hold on to these light elements.

  11. With the loss of their lightest elements, planets and moons shrink while their overall densities increases.

  12. The density of a planet or moon is not an arbitrary value. The terrestrial planets, the Earth's moon, and the Galilean moons have evolved the most to produce the highest densities. Most non evolved moons are essentially extremely dirty ice balls and so they have densities slightly greater than the density of ice at around 1.1 g/cm3. The density values are slightly higher for the outermost planets and the outermost moons of the satellite systems because these outer objects collect the most incoming metallic dust.

  13. Planetary evolution does not go on forever. Mercury, Mars, and the Earth's moon are now geologically dead because the internal heat is inadequate for the light volcanic material to continue migrating to the surface.

  14. All of the Earth's surface water originated from the Earth's interior. The water emerging from mid-ocean ridges, most volcanoes, and at hot mineral springs is not recycled water but rather it is water making a one way trip from the Earth's interior to its surface.

  15. Once gaseous water is released on the surface of a planet or moon it is exposed to the Sun's ultraviolet radiation that breaks the water molecule apart, and because of this there is no water on the surface of most planets and moons. After the water molecule is broken apart, the hydrogen escapes out to space while the highly reactive oxygen bonds with minerals on the surface.

  16. On Earth, so much water was being released on the surface that life was able to evolve before ultraviolet radiation destroyed all the water. Life produced diatomic oxygen that, along with ozone, accumulated in the stratosphere. This O2 and O3 oxygen in the atmosphere blocked UV radiation from reaching Earth's surface thus shielding the Earth's water from being broken apart by UV radiation. This allowed Earth to become a unique planet with most of its surface covered with water.

  17. Another consequence of life evolving on Earth was the removal of nearly all of the carbon dioxide that once filled the Earth's atmosphere. While the typical terrestrial planet such as Venus and Mars have atmospheric compositions consisting of around 96.5% carbon dioxide and 3.5% nitrogen, Earth has an atmospheric composition of 78% nitrogen, 21% oxygen, and 1% argon.

  18. Since the vast majority of Earths earlier atmosphere was carbon dioxide and nearly all of this has been removed, the Earth's present atmosphere is substantially thinner than what is was before.

  19. Nearly all of the carbon dioxide that once filled the atmosphere is now locked away in carbonated rocks and coal deposits.