8.4: The Aftermath of Planet Formation
Where did Asteroids and Comets Come From?
Asteroids are leftover planetismals of the inner solar system
Probably enough objects in the asteroid belt to from another terrestrial planet in the past
but because most of them crashed into the inner planets, that is no longer possible.
Comets, are icy left over planetismals of the outer solar system, and must have initially
populated the entire outer solar system beyond Neptune
Object orbiting beyond Neptune should have been able to grow in size without any
disruption, some growing large enough to be considered dwarf planets; they now occupy
the Kuiper belt.
Close encounters with Jovian planets caused comets to suffer close gravitational
encounters causing them to be kicked out into random orbit far from the Sun, which is
why they now populate the Oort cloud
The Heavy Bombardment:
Impact crater played a critical role in our existence because it brought materials from
other regions of the solar system.
When planets were formed it was only comprised of metal and rock, no water or other
hydrogen compounds because it was too hot for the compounds to condense in this
Earth and other terrestrial planets received its water because water and other hydrogen
compounds were brought in from water bearing planetismals that accreted farther from
Not easy for a planet to capture a moon, unbound object can’t become a bound object
unless orbital energy is lose somehow
Jovian planets probably captured when passing planetismals lost energy because they
were trying to drag in the disks of gas that surrounded the planets as they formed
Gas would cause friction causing the planetismals to slow down. If it was slowed down
enough, it could have become an orbiting moon