The Remarkable Design of the Solar System’s Turbulent Youth, Part 2

The Remarkable Design of the Solar System’s Turbulent Youth, Part 2

In part 1 of this series on the solar system’s youth I described the solar system’s exquisitely fine-tuned birthing experience. Here, in part 2, I will describe amazing events that took place in the solar system’s toddlerhood. As with the solar system’s birthing experience, these events had to be perfectly fine-tuned in order for advanced life on Earth to have a chance.

Just-Right Gas Giant Planets

The solar system requires a very particular suite of gas giants for a planet like Earth to be possible. For example, about a decade ago, a team of five American and Canadian astronomers discovered that the nature of a planetary system’s small rocky planets is usually the result of how efficiently the local gas giants dynamically excite the rocky planet embryos.1 Increased excitement in the embryos results in fewer rocky planets that are more massive and the closer to the central star. For advanced life to be possible this excitement level must be just right.

A suite of gas giants is also essential to protect life on a habitable rocky planet from taking too many destructive hits from asteroids and comets. Such a group of planets acts like a gravitational shield for the habitable planet; their gravitational potentials either deflect projectiles away form the habitable planet or result in they themselves absorbing comets and asteroids.2

However, if the gas giant planets are either too small or too distant, the shielding will be inadequate. On the other hand, if they are too large or too close, their gravitational potentials will disrupt the habitable planet’s orbit.

Our solar system’s suite of gas giant planets (Jupiter, Saturn, Uranus, and Neptune) had to exhibit the just-right masses, just-right distances from the Sun, and just-right orbital configurations so Earth’s own mass, distance from the Sun, and orbital features could be just-right for supporting advanced life. At the same time, the gas giant planets must be designed to provide optimal gravitational shielding for our home planet.

Just-Right Moon-Forming Event

As I described in part 1, extraordinary events during the solar system’s birth led to the Sun’s planets becoming extremely volatile-poor and refractory-rich. But though those events rid Earth of most of  its volatiles, they still left our planet with far too much water and far too thick an atmosphere for it ever to support advanced life. Something truly outstanding must have occurred soon after Earth’s formation to scrub away nearly all its remaining volatiles so as to make it a fit candidate for sustaining plants, animals, and people. Enter the Moon-forming event.

The Moon’s anomalous nature has intrigued astronomers for centuries. Compared to the mass of its planet, the Moon is fifty times larger than any other moon in the solar system. Dynamical models in use during my graduate school days all predicted that the Moon was impossible. Our Moon was too large, too close to Earth, and Earth too close to the Sun for the Moon to ever form out of the Sun’s protoplanetary disk. All collision scenarios either resulted in the destruction of Earth, failure to form the Moon, or the formation of an Earth-Moon system with orbital features radically different from what astronomers observe. At the time, some researchers went so far as to concede that the Moon must be some kind of miracle.

Today, astronomers understand that the existence of the Moon does not violate any of the laws of physics. Nevertheless, the conditions under which the Moon formed are so remarkable as to render it an excellent example of supernatural design for humanity’s specific benefit. In order for the Moon to form, Earth needed to receive a just-right impactor at the just-right time under just-right conditions and circumstances (see figure 1). Astronomers call the impactor Theia.

In order for the impact to generate a debris disk from which a lunar-sized satellite could form, vapor gases could not dominate that debris disk.3 Such gases generate spiral shocks that lead to the destruction of circumterrestrial disks (a debris disk surrounding Earth) within just a few days. Fortunately, the planets’ low volatile levels helped limit the quantity of available vapor gases. But even without significant quantities of volatiles, a gas-dominated circumterrestrial disk still could have occurred if the impact energy was high. High impact energy would have vaporized the rocky material either in Earth, the impactor, or both.

But several just-right circumstances limited the impact energy. Primordial Earth was slightly smaller than its present size at the time of the impact and the impactor itself was no more than about 20 percent of Earth’s mass. Plus, the collision impact angle was about 45 degrees and the impactor velocity was less than 12 kilometers per second. If any of these circumstances had differed too greatly, the impact energy would have been too high.

In 2000, planetary astrophysicists William Ward and Robin Canup confirmed that the Moon’s substantial orbital inclination relative to Earth’s equator could be explained only if the Moon formed out of an impact-generated circumterrestrial disk.4 In 2001, Canup and Erik Asphaug used a method known as smooth particle hydrodynamics to produce a model for Moon formation that correctly predicted the Moon’s low iron amounts5 as well as the mass and angular momentum for both the Moon and Earth.6 This model established that the Moon formed near the very end of Earth’s accumulation of material from the Sun’s protoplanetary disk. That is, the Moon must have formed between 30 and 50 million years after Earth’s initial formation.

In 2004, Canup produced a much more detailed model for Moon formation.7 She achieved her best results for a collision impact angle of 45 degrees, an impactor mass between 0.11 and 0.14 Earth masses (Mars = 0.11 Earth masses), and an impactor velocity relative to Earth of less than 4 kilometers per second (typical meteorite velocities relative to Earth = 50 kilometers per second).

Canup continued her research and in 2008, developed the most detailed and accurate model to date for the Moon’s formation. For the first time she took into account the rotation rate and the direction of rotation for both the impactor and the toddler Earth.8 She achieved the best match for the current Earth-Moon system’s angular momentum with an impactor up to nearly twice the mass of Mars colliding into a retrograde rotating proto-Earth.

Two Japanese astronomers have also contributed to scientists’ understanding of the Moon-formation event. They demonstrated that a deep liquid water ocean on primordial Earth’s surface ensured that the Moon-forming impact blasted away enough of the planet’s initial atmosphere and ocean.9 Deep liquid water at the impact site lowered the shock impedance compared to bare ground. Thanks to a low shock impedance and plentiful water, the impact generated a huge amount of superheated steam, which ejected almost all Earth’s primordial water and atmosphere into interplanetary space. To guarantee that neither too much nor too little of Earth’s primordial atmosphere and ocean is removed, the primordial ocean depth had to be extremely fine-tuned.

The shock impedance also had to be fine-tuned to not only remove the just-right amounts of water and atmosphere, but also ensure that the just-right amounts of the heavier elements (especially iron, uranium, and thorium) were transferred from the collider into Earth’s core and mantle. In order for the shock impedance to be sufficiently low to make all this happen, the collider, as already confirmed by Canup’s models, had to strike Earth at a low impact angle and a very low velocity.

It is challenging, to say the least, to develop a solar system scenario that would produce such an exquisitely fine-tuned collision. Some researchers try to explain it by suggesting that the collider actually shared Earth’s orbit about the Sun. Newtonian mechanics allows for this possibility at either the L4 or L5 Lagrange points (see figure 2). A smaller planet situated 60 degrees back or forward along Earth’s orbit can remain there in a stable orbital configuration, providing the Sun is at least 25 times more massive than Earth. Since the Sun is actually 333,400 times more massive, the stability condition is easily met.  

Joseph-Louis Lagrange, a French mathematician, discovered that Newtonian mechanics allows for five special points in the vicinity of two orbiting masses where a third, smaller mass can orbit at a fixed point from the larger masses. Of the five points only two, the L4 and L5, are stable over long time periods.

The stability condition assumes, however, that only three massive bodies are involved. The presence of other planets in the solar system, particularly the presence of Jupiter and/or nearby planetesimals, means that given sufficient time the smaller planet sharing Earth’s orbit would have been wriggled away slightly from its Lagrange point. When this happened, there existed a substantial possibility that the smaller planet crept toward Earth and eventually collided with it at a low velocity and a low impact angle.

The Moon-forming impact presents all humanity with a dramatic set of evidences for supernatural, super-intelligent design for our specific benefit. Thanks to the exquisitely fine-tuned nature of this impact event, the collision:

  1. Replaced Earth’s thick, suffocating atmosphere with one that possesses the perfect air pressure for efficient lung performance,10 ideal heat-trapping capability, and just-right transparency for efficient photosynthesis.
  2. Gave the new atmosphere the optimal chemical composition to foster advanced life.
  3. Augmented Earth’s mass and density enough to allow it to gravitationally retain a large, but not too-large, quantity of water vapor for billions of years.
  4. Raised the amount of iron in Earth’s core close to the level needed to provide the planet with a strong, enduring magnetic field (the remaining iron came from a later collision event—see part 3 in this series). This magnetic field shields life from deadly cosmic rays and solar x-rays.
  5. Delivered to Earth’s core and mantle quantities of iron and other critical elements in just-right ratios to produce sufficiently long-lasting, continent-building plate tectonics at just-right levels. (Fine-tuned plate tectonics also perform a crucial role in compensating for the Sun’s increasing brightness.11)
  6. Increased the iron content of Earth’s crust, permitting a huge abundance of ocean-dwelling phytoplankton that in turn supports the entire oceanic food chain and provides the oxygen for advanced terrestrial life.12
  7. Salted Earth’s interior with an abundance of long-lasting radioisotopes, the heat from which drives most tectonic activity and volcanism.13
  8. Produced the Moon, which gradually slowed Earth’s rotation rate so that eventually advanced life could thrive.14
  9. Produced a Moon with the just-right mass and distance relative to Earth to stabilize the planet’s rotation axis tilt, protecting the planet from rapid and extreme climatic variations.15
  10. Produced a Moon with the just-right diameter and distance relative to Earth so that humans would witness perfect solar eclipses during the narrow epoch in solar system history when human life is possible.16 

Clearly, we humans have a lot to thank God for in the different ways He designed and timed the Moon-forming impact event. If it was not for the fine-tuning of that event and of the Moon’s present-day properties, we, and our high-technology civilization, would be impossible. On Earth’s birthday 4.5662 billion years ago and the Moon’s origin 4.53 billion years ago, God was expressing His great love for us all. In part 3 of this series I will describe additional miraculous events that occurred during the solar system’s youth—the epoch between 50 million to a billion year after the solar system’s birthday—that further prepared Earth to receive advanced life.

Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6
  1. Harold F. Levison and Craig Agnor, “The Role of Giant Planets in Terrestrial Planet Formation,”Astronomical Journal 125 (May 2003): 2692–713; H. Levison et al., “The Role of Giant Planets in Terrestrial Planet Formation,”Bulletin of the American Astronomical Society 33 (November 2001): 1198.
  2. Hugh Ross, More Than a Theory (Grand Rapids: Baker, 2009), 125–27.
  3. Keiichi Wada, Eiichiro Kokubo, and Junichiro Makino, “High-Resolution Simulations of a Moon-Forming Impact and Postimpact Evolution,”Astrophysical Journal 638 (February 20, 2006): 1180–86.
  4. William R. Ward and Robin M. Canup, “Origin of the Moon’s Orbital Inclination from Resonant Disk Interactions,”Nature 403 (February 17, 2000): 741–43.
  5. Paul G. Lucey, G. Jeffrey Taylor, and Erick Malaret, “Abundance and Distribution of Iron on the Moon,”Science 268 (May 26, 1995): 1150–53.
  6. Robin M. Canup and Erik Asphaug, “Origin of the Moon in a Giant Impact Near the End of the Earth’s Formation,”Nature 412 (August 16, 2001): 708–12.
  7. Robin M. Canup, “Simulations of the Late Lunar-Forming Impact,”Icarus 168 (April 2004): 433–56.
  8. Robin M. Canup, “Lumar-Forming Collisions with Pre-Impact Rotation,”Icarus 196 (August 2008): 518–38.
  9. Hidenori Genda and Yutaka Abe, “Enhanced Atmospheric Loss of Protoplanets at the Giant Impact Phase in the Presence of Oceans,”Nature 433 (February 24, 2005): 842–44; Kevin Zahnle, “Planetary Science: Being There,”Nature 433 (February 24, 2005): 814–15.
  10. Michael J. Denton, Nature’s Destiny (New York: The Free Press, 1998), 127–31, 251–52.
  11. Hugh Ross, More Than a Theory, 156–71.
  12. Louis A. Codispoti, “The Limits to Growth,”Nature 387 (May 15, 1997): 237; Kenneth H. Coale et al., “A Massive Phytoplankton Bloom Induced by an Ecosystem-Scale Iron Fertilization Experiment in the Equatorial Pacific Ocean,”Nature 383 (October 10, 1996): 495–99.
  13. Peter D. Ward and Donald Brownlee, Rare Earth (New York: Copernicus, Springer-Verlag, 2000), 191–234.
  14. Dave Waltham, “Anthropic Selection for the Moon’s Mass,” Astrobiology 4 (December, 2004): 460–68.
  15. William R. Ward, “Comments on the Long-Term Stability of the Earth’s Obliquity,” Icarus 50 (May–June 1982): 444–48; Carl D. Murray, “Seasoned Travellers,”Nature 361 (February 18, 1993): 586–87; Jacques Laskar and P. Robutel, “The Chaotic Obliquity of the Planets,”Nature 361 (February 18, 1993): 608–12; Jacques Laskar, F. Joutel, and P. Robutel, “Stabilization of the Earth’s Obliquity by the Moon,”Nature 361 (February 18, 1993): 615–17.
  16. Hugh Ross, More Than a Theory, 137.