Earth & Theia Collision
Theia is a hypothetical planet that formed in the early solar system and is thought to have collided head-on with the early Earth around 4.5 billion years ago. It was roughly the size of Mars, having a diameter of 6,102 km. Theia was traveling about 4 km/s, and possibly hit Earth at a 45 degree angle. The collision is also theorized to have created the Moon.
(Note: This is my best attempt at recreating the collision, and I couldn’t get Theia to travel at 4 km/s. It’s more like 25 km/s). 🙁