The Most Important Impact Event in the History of the Solar System
The universe may mostly be empty space, but if we have all the time to observe it, we are bound to see objects clashing onto each other causing a massive impact to where it is. Join us in this episode as we take a journey to know more about what happens when worlds – LITERALLY – collide.
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As the Solar System evolved from a simple cloud of dust swirling around a proto star, to what we know it today, it is unavoidable that a lot of space objects will eventually collide with one another. It’s just basic thermodynamics. The amount of disorder will increase over time.
We call these collisions cosmic impact, or impact events. These happen when astronomical objects such as asteroids, planets, meteorites, and comets – generally speaking – crash into one another, resulting in scalable impact around it. This effect can vary from a simple creation of a crater on a planetary surface, like what we see on the Moon, or to something as grand as the creation of a new moon, like what happened to the Earth when the asteroid Theia collided with it.
These events are fairly regular to our Solar System, but the one of the biggest of them all, the one that brought a massive change, was the event that we poetically call, The Late Heavy Bombardment: a hypothesized event in the Solar System’s history where a large number of planetesimals, like comets, meteors and asteroids collided with other planets, particularly the terrestrial ones, producing massive effects.
This is a very aggressive period in the timeline of our Solar System, especially to the inner planets, since they – or we – are the ones that gravely experienced this cataclysmic event.
For the sake of the video, and since saying “The Late Heavy Bombardment” is such a tedious task, we will refer to this event as LHB from this point moving forward. We’re the generation of abbreviations anyway, aren’t we?
What caused the LHB?
To fully understand what resulted to the LHB, we need to go back to when our Solar System was still at its infant stages, before there were planets and moons moving about.
Like all stellar systems, our very own sun once began as a young star surrounded by a cloud of dust and gas which we collectively spin around to form a protoplanetary disc.
Some particles garner in the disc clumped together, and due to their own weak gravity, they formed pebble-sized planetesimals, which then attracted more and more of its kind, and a few other particles, eventually forming what we know today as planets, asteroids, dwarf planets and comets.
The planets attempt to stabilize their own orbits, and the very first ones to be successful at this feat are the inner planets: Mercury, Venus, Earth and Mars.
But what about the Jovian planets? Well, they’re an entirely different story. Now, we are getting closer to the LHB.
Enter our two giants, Jupiter and Saturn. At the early stages, their orbits were extremely unstable, as it is still trying to find a “sweet spot”, or in a manner it can move at a constant speed without disturbance. Because of how their orbits influenced one another, it produced an effect that scientists call a 2:1 resonance, meaning every 1 part of Jupiter’s orbit equates to 2 parts of Saturn’s. This caused an irregularity in the gravitational force to the objects that are close to them.
Now, enter to the picture our two last planets, Uranus and Neptune.
Neptune wasn’t always the “youngest” in the Solar System, being placed in last. Once upon a time, it was closer to the Sun, and Uranus was actually the last planet in the line.
But because of the resonance from the two large planets, it was destabilized out of its orbit until it was pushed away to the farthest region of the Solar System.
At this place, the planetesimals were still moving about. Since Neptune was sent out to their area, it caused a disturbance in their constant motion, and a lot of the planetesimals were kicked away to different directions. Space debris was flying everywhere. Some moved away from the Solar System, while others moved towards the inner planets, and became the components of the Late Heavy Bombardment.
This is the most popular hypothesis on what possibly caused the LHB. There are several others that attempt to give an explanation, such as: the late formation of the outermost planets, Uranus and Neptune; the presence of a fifth inner planet with an unstable orbit, and; the disruption of an asteroid crossing Mars.
Lunar Cataclysm: The AKA of the LHB
Another terminology used to refer to the Late Heavy Bombardment was Lunar Cataclysm, as this event heavily changed the topology of the Moon.
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