An encounter with 'something outside of the solar system' may have triggered an ice age on Earth

Scientists believe Earth may have briefly lost protection from the sun around two million years ago, left to endure the extreme environment of interstellar space as the solar system passed through a dense cloud of gas and dust between stars.

At that time, early human ancestors shared our planet with prehistoric Animals like mastodons and sabretooth tigers. It's also when Earth was in the midst of the ice age that ended only around 12,000 years ago. Ice ages are brought about by a range of factors, including our planet's tilt and rotation, carbon dioxide levels in its atmosphere, and shifting plate tectonics and volcanic eruptions at its surface. However, given the timing of when scientists think Earth plunged through interstellar space, this research suggests radical changes in our planet's climate, like the onset and ending of ice ages, could also be iNFLuenced by the position of our solar system in our home galaxy.

More specifically, the team behind the new findings suggests the solar system could have encountered a dense patch of interstellar gas and dust as it traversed the Milky Way two million years ago. And that patch may have been thick enough to interfere with a stream of charged particles called the "solar wind" flowing from the sun and impacting Earth, potentially causing plunging temperatures.

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"This paper is the first to quantitatively show there was an encounter between the sun and something outside of the solar system that would have affected Earth's climate," research lead author Merav Opher, a space physicist and expert on the heliosphere at Boston University, said in a statement.

The solar system, back in time

Our entire solar system is enveloped in a "giant bubble" of protective plasma that comes from the sun, which is known as the "heliosphere." This protective shield is created when solar winds press on the interstellar medium, which refers to stuff that drifts through the spaces between stars in the Milky Way. The heliosphere is perpetually refreshed by a constant flow of charged particles from the sun, which stream out past Pluto.

The heliosphere shields Earth's surface from radiation and galactic rays that could potentially impact the DNA of living things. This shielding is so crucial that many scientists believe it was integral to the emergence and evolution of life on Earth.