The Pleistocene Epoch, known for its ice ages, mammoths, and early humans, still holds sway in our planet’s past, ending only 12,000 years ago. Now, scientists suggest that this era’s icy grip might have been influenced by a cosmic cloud that briefly shielded Earth from the Sun’s warmth.
Around two million years ago, a team of researchers suggests, a space cloud disturbed our solar system, pushing Earth and other planets beyond the protective shield of the Sun’s heliosphere, the bubble of charged particles around our system. These findings are published in Nature Astronomy.
Merav Opher, an astrophysicist at Boston University and the lead author of the research stated, “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.”
In an email to Gizmodo, he also said that the team is currently working on refining their analysis using contemporary climate models. They suggest that with elevated levels of hydrogen and dust, Earth would have potentially entered into an ice age.
Solar system may have passed through the constellation Lynx
Using data from the HI4PI survey, Opher’s team simulated that our solar system likely traversed through the Local Ribbon of Cold Clouds situated in the constellation Lynx around 2 to 3 million years ago.
Notably, the Pleistocene era commenced approximately 2.6 million years ago. While it remains uncertain if such cold clouds directly triggered an ice age, the research mentioned, further evidence of cloud interactions with the heliosphere could shed light on the potential impacts on Earth.
Approximately 3 million years ago, a dense interstellar cloud collided with the Solar System, significantly compressing the heliosphere—the sun’s protective magnetic bubble that shields Earth and other planets from cosmic dangers. This event posits that the heliosphere’s size was… pic.twitter.com/JwmzgkOJJ0
— Erika (@ExploreCosmos_) June 10, 2024
Based on the team’s model, during such a journey, the protective heliosphere surrounding Earth and nearby planets would contract to approximately 0.22 astronomical units, which is less than a quarter of the distance from Earth to the Sun.
To grasp the significance, the European Space Agency (ESA) estimates the current closest boundary of the heliosphere to be around 100 astronomical units from the Sun, roughly twice the distance of the Kuiper Belt.
Earth would have been exposed to iron and plutonium
The team suggested that beyond the heliosphere, Earth would have been exposed to iron and plutonium from the interstellar medium.
Moreover, their analysis corresponds with a rise in the levels of plutonium-244 and iron-60, two isotopes of these elements commonly associated with cosmic events, found in Antarctic snow, deep-sea sediments, and samples from the Moon.
Additionally, Opher noted that if samples from Mars were examined similarly to those from the Moon and Earth, they might also show a comparable increase in the iron isotope roughly two to three million years ago.