Researchers suggest that Earth may have been affected by interstellar clouds, leading to the development of multiple ice ages. According to astrophysicists from Boston University, Harvard University, and Johns Hopkins, our solar system encountered a massive and dense interstellar cloud approximately two million years ago. This encounter exposed Earth to radiation, which altered its climate. While various factors contribute to ice ages, such as the planet’s tilt, carbon dioxide levels, and tectonic plate movement, this is the first time interstellar clouds have been considered as a potential cause. Merav Opher, an astronomy professor at Boston University and fellow at Harvard Radcliffe Institute, stated that this research is the first to provide quantitative evidence of an encounter between the sun and an external factor that impacted Earth’s climate.
The heliosphere, a protective bubble surrounding our solar system, shields us from harmful radiation and cosmic rays that could impact our DNA. This shield is composed of charged particles known as the solar wind, emitted by the sun.
Recently, researchers have proposed that an interstellar cloud may have caused the heliosphere to contract, leaving Earth exposed to radiation from the galaxy and potentially cooling the climate.
To investigate this hypothesis, the team utilized computer modeling to determine the Sun’s position two million years ago. They also analyzed data from the Gaia Satellite to track the movement of the Local Ribbon of Cold Clouds, a collection of large, dense, and extremely cold hydrogen clouds.
One particular cloud, known as the Local Lynx of Cold Cloud, may have come into contact with the heliosphere and caused its collapse.
The absence of the heliosphere’s protection would have exposed Earth to the interstellar medium, potentially impacting our planet’s atmosphere with a mixture of gas, dust, and remnants of exploded stars, such as iron and plutonium.
Geological evidence supports this theory, as higher levels of iron-60 and plutonium-244 isotopes have been found in the ocean, on the moon, in Antarctic snow, and within ice cores from the same time period. These isotopes originate from supernovae explosions and are commonly found in interstellar clouds. Hence, it is likely that they were deposited on Earth during the time it was outside the protective heliosphere.
The researchers estimate that Earth remained outside the heliosphere for approximately 10,000 years. This suggests that our planet encountered the interstellar medium during this period.
Dr. Opher, one of the researchers, stated, “This cloud was indeed in our past, and if we crossed something that massive, we were exposed to the interstellar medium.”