Emily Chan
They went back in time to observe the position of the sun two million years ago, along with the location of the heliosphere and the rest of the solar system.
They also tracked the path of the Local Ribbon of Cold Clouds system, a string of thick, cold clouds mostly made of hydrogen atoms.
Their simulations revealed that one dense cloud close to the end of that ribbon could have collided with the heliosphere.
As a result of the collision, Earth would have been left fully exposed to the interstellar medium, where dust and gas combine with the remains of exploded stars, which include iron and plutonium.
Usually, the heliosphere would block these particles, but without its protection, these radioactive elements could reach Earth easily.
This aligns with the increase of iron and plutonium isotopes in the ocean, Antarctic snow, ice cores, and on the moon during that same time period. It also corresponds with temperature records that indicate a cooling period on Earth.
It’s impossible to determine the exact impact the cold cloud had on our planet. The scientists don’t know for sure whether it could’ve truly triggered an ice age.
So, for now, they will continue investigating other interstellar clouds further back in time to see if they line up with ice ages.
You can read the study here.
