Around two million years ago, Earth experienced multiple ice ages, leading to a deep freeze that lasted until about 12,000 years ago. While scientists have attributed these ice ages to various factors such as Earth’s tilt, volcanic eruptions, and carbon dioxide levels, a new study led by researchers at Boston University suggests that the sun’s location in the galaxy may have played a significant role in shaping Earth’s climate.
Published in Nature Astronomy, the study proposes that approximately two million years ago, the solar system encountered a dense interstellar cloud that could have disrupted the sun’s solar wind. This event may have temporarily pushed Earth and the other planets outside the protective bubble known as the heliosphere, exposing them to potentially harmful radiation and galactic rays.
According to Dr. Merav Opher, a space physicist at BU and the lead author of the study, this research is the first to quantitatively demonstrate the impact of an external encounter on Earth’s climate. By using sophisticated computer models, the researchers traced the path of the Local Ribbon of Cold Clouds system, which consists of large, dense clouds primarily made of hydrogen atoms. One of these clouds, known as the Local Lynx of Cold Cloud, was found to have potentially collided with the heliosphere.
The study suggests that if Earth was indeed exposed to the interstellar medium without the protection of the heliosphere, it could explain the presence of increased levels of iron-60 and plutonium-244 isotopes in geological records from that time period. These findings align with temperature records indicating a cooling period, hinting at a possible link between the interstellar cloud encounter and Earth’s climate.
While the exact effects of the interstellar cloud on Earth remain uncertain, Dr. Opher and her team are actively investigating the potential implications on radiation, atmosphere, and climate. By analyzing data from the European Space Agency’s Gaia mission, which maps the movements of stars in the galaxy, the researchers aim to further understand how external forces have influenced Earth’s history.
This groundbreaking research sheds new light on the complex relationship between the solar system and the surrounding interstellar environment. As Dr. Opher notes, this study marks only the beginning of a deeper exploration into how Earth has been shaped by cosmic phenomena throughout its history. Through continued research and analysis, scientists hope to unravel more mysteries surrounding our planet’s past interactions with the wider universe.