Some 13.8 billion years ago, there was a big bang and spacetime came into existence. The hot dense material spread and started cooling down, forming massive clouds of stardust. About 4.5 billion years ago, a solar nebula — a giant cloud of interstellar gas — gave birth to our sun and other solar system planets. However, the formation of planets was not so straightforward as it has been always thought. Scientists believe that clumps of stardust collided to give rise to bigger space rocks and then over time, the planets accumulated the mass from collisions that came their way. The picture we knew till now was simple — for example, whenever something collided with Earth, it stuck around and gave rise to the planet’s mass.

Now, a new study challenges this notion. According to a team of scientists, sticking around after a collision was not so simple. Using computer models, scientists simulated giant collisions that took place in the early days of the solar system and found that the early collisions followed a “hit-and-run-return” scenario. This means, when big bodies in the solar system collided, they did not stick, they hit each other and ran. However, because the collision slowed them down, they came back, and this time it was to stick around.