~4 billion years agoReputable sourceDebated
The Late Heavy Bombardment
On the timeline · around ~4 billion years ago · The Solar System & Us
What happened
Around 4 billion years ago, the young Earth and its neighbours may have endured an intense spike of asteroid and comet impacts — possibly triggered when the giant planets' orbits shifted and scattered debris across the inner Solar System.
Why it matters
These impacts scarred the Moon and planets and reshaped the early Earth, perhaps even influencing where and when life could first take hold.
How we know
The idea comes from the ages of Moon rocks returned by the Apollo missions. Whether it was a true spike, a gradual decline, or didn't happen at all is still debated.
Sources
- NASA. What is the Late Heavy Bombardment? · Reputable source
Related timelines
- Evolution of Life on Earth → — The battered young world where life would arise