What is the late heavy bombardment?
The lunar cataclysm, often referred to as the Late Heavy Bombardment or LHB, is believed to have taken place between 4.1 and 3.8 billion years (Ga) ago, during the Neohadean and Eoarchean epochs on Earth. It is hypothesised that during this time, a disproportionately large number of asteroids struck Mercury, Venus, Earth, and Mars, as well as other early terrestrial planets in the inner Solar System.
The Late Heavy Bombardment took place very early in Earth's history, after the Earth and other rocky planets had formed and accrued the majority of their mass.
The story of the late heavy bombardment
Numerous smaller solar system objects, such as asteroids, are thought to have been pushed along by the giant planets as they moved about and orbited closer to and distant from the sun, causing the Late Heavy Bombardment, according to the majority of researchers. But, why that?
well, to answer this question we need to go back to when our Solar System was still at its infant stages, before there were planets and moons moving about.
- Our own sun was once a newborn star, like all stellar systems, encircled by a cloud of gas and dust that we now collectively spin to form a protoplanetary disc.
- The disc contained some particles that clumped together and, due to their own weak gravity, created planetesimals the size of pebbles. These planetesimals attracted other particles of their kind as well as a few other particles, eventually creating what we now know as planets, asteroids, dwarf planets, and comets.
- The outer planets (Jupiter, Saturn, Uranus and Neptune) have a different story :
- Uranus and Neptune :- Neptune wasn't always the last planet in the Solar System, making it the "youngest" planet.
- When the planet was once closer to the Sun, Uranus was the last one in the line. However, due to the resonance from the two giant planets, it was knocked out of its orbit and flung as far as the Solar System's furthest reaches. The planetesimals were still moving about at this location. A lot of the planetesimals were sent away in various directions since Neptune's arrival in their region disrupted their steady speed. There was flying space junk everywhere. Some migrated outside the Solar System, while others migrated inside it and ended up as parts of the LHB.
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