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Earth's Climate May Have Been Affected by Interstellar Clouds 2 Million Years Ago
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Earth's Climate May Have Been Affected by Interstellar Clouds 2 Million Years Ago
by Amcen West
Boston MA (SPX) Jun 10, 2024

Around two million years ago, Earth experienced multiple ice ages, coinciding with significant climatic changes. Scientists propose that these ice ages were caused by factors such as the planet's tilt, rotation, plate tectonics, volcanic eruptions, and atmospheric carbon dioxide levels. A new study suggests that the sun's position in the galaxy could also have influenced Earth's climate.

In a paper published in Nature Astronomy, astrophysicist Merav Opher, a professor at Boston University and fellow at Harvard Radcliffe Institute, provides evidence that the solar system encountered a dense interstellar cloud around two million years ago, potentially affecting the sun's solar wind. Opher and her team believe this shows that the sun's location in space might play a significant role in shaping Earth's climate history.

The solar system is surrounded by the heliosphere, a protective plasma shield created by the sun's solar wind. This heliosphere protects Earth and other planets from radiation and galactic rays that can alter DNA. According to the study, a cold interstellar cloud compressed the heliosphere, exposing Earth and other planets to the interstellar medium.

"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," said Opher. Her research focuses on the heliosphere and how it is structured by the solar wind interacting with the interstellar medium. Her theory, which describes the heliosphere as a puffy croissant, has been influential in the space physics community. She is now investigating how the heliosphere and the sun's movement through space could affect Earth's atmospheric chemistry.

"Stars move, and now this paper is showing not only that they move, but they encounter drastic changes," said Opher, who began this study during a fellowship at Harvard Radcliffe Institute.

To examine this phenomenon, Opher and her collaborators used computer models to visualize the sun's position two million years ago, along with the heliosphere and the solar system. They mapped the path of the Local Ribbon of Cold Clouds system and identified a dense cloud, the Local Lynx of Cold Cloud, that could have collided with the heliosphere.

If this collision occurred, Earth would have been exposed to the interstellar medium, which contains elements from exploded stars, including iron and plutonium. Normally, the heliosphere filters out most of these particles, but without its protection, they could reach Earth. The study aligns with geological evidence of increased 60Fe (iron 60) and 244Pu (plutonium 244) isotopes found in oceans, on the moon, in Antarctic snow, and in ice cores from that period, matching temperature records indicating a cooling phase.

"Only rarely does our cosmic neighborhood beyond the solar system affect life on Earth," said Avi Loeb, director of Harvard University's Institute for Theory and Computation and coauthor of the paper. "It is exciting to discover that our passage through dense clouds a few million years ago could have exposed the Earth to a much larger flux of cosmic rays and hydrogen atoms. Our results open a new window into the relationship between the evolution of life on Earth and our cosmic neighborhood."

The pressure from the Local Lynx of Cold Cloud could have blocked the heliosphere for up to a million years. Once Earth moved away from the cloud, the heliosphere resumed its protective role.

The exact impact of the cold clouds on Earth's climate is unclear, but Opher suggests that the sun has likely encountered other cold clouds throughout its history and will do so again. Opher and her team are now tracing the sun's position seven million years ago and further back, using data from the European Space Agency's Gaia mission, which is mapping the galaxy in 3D and tracking star movements.

"This cloud was indeed in our past, and if we crossed something that massive, we were exposed to the interstellar medium," said Opher. Her team at BU's NASA-funded SHIELD DRIVE Science Center is exploring the effects on Earth's radiation, atmosphere, and climate.

"This is only the beginning," said Opher. She hopes the paper will inspire further exploration of how the solar system's past encounters with interstellar clouds have influenced life on Earth.

Research Report:A possible direct exposure of the Earth to the cold dense interstellar medium 2-3 Myr ago

Related Links
Harvard Radcliffe Institute
Stellar Chemistry, The Universe And All Within It

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