This is the time of year when we start thinking about cold snaps – frontal systems that cause sudden drops in temperature, and often bring clouds.

A recent study suggests that our entire planet went through a major cold snap a few million years ago. It was caused by a giant cloud – a dense clump of material between the stars.

The space between stars contains many clouds of gas and dust. In fact, we’re inside one right now – the Local Interstellar Cloud. But it’s quite thin, so it doesn’t have much impact on the solar system.

The study says we might have passed through a much thicker cloud two million to three million years ago. Its material could have been 15 thousand times denser than the current cloud.

That could have drastically squeezed the magnetic “bubble” generated by the Sun. Today, the bubble extends more than a hundred times the distance from Earth to the Sun. But in the denser cloud, it could have been squeezed to just a quarter of the Earth-Sun distance.

Since Earth would have been outside the Sun’s protective bubble, it would have been bombarded by more cosmic rays. And dust from the interstellar cloud might have settled into our atmosphere.

The researchers say that could have had an impact on Earth’s climate – perhaps making it much cooler. That could have killed off some life, and perhaps altered the development of human ancestors – possible impacts of an interstellar cold snap.

Script by Damond Benningfield