Earth's climate might be influenced by sun's passage through dense interstellar cloud

New research suggests the Earth's climate might have been dramatically influenced by the sun's passage through a dense interstellar cloud millions of years ago, Azernews reports.

The study published Monday in Nature Astronomy provides fresh insights into how our solar system's movement through the Milky Way could affect the Earth's climatic history.

The sun, as it travels around the center of the Milky Way, oscillates relative to the galactic plane.

The motion might have led the solar system through regions of space dense enough to interfere with the solar wind, potentially cooling the Earth, according to the study.

"The Sun sends out a constant flow of charged particles called the solar wind, which ultimately travels past all the planets to some three times the distance to Pluto before being impeded by the interstellar medium," NASA said on its official website. "This forms a giant bubble around the Sun and its planets, known as the heliosphere.”

NASA said that currently, the solar system resides within the 1,000-light-year-wide "Local Bubble," a region with a sparse particle density; however, the solar system will exit the bubble and reenter the denser ISM (interstellar medium) in a few thousand years.

Researchers have found evidence suggesting we have traversed denser regions in the past, the study revealed.

"In the ISM that the Sun has traversed for the last couple of million years, there are cold, compact clouds that could have drastically affected the heliosphere," the team explained in the study.

"We explore a scenario whereby the Solar System went through a cold gas cloud a few million years ago," it stated.

The research reported that such an encounter could have contracted the heliosphere, allowing more ISM material to reach Earth's atmosphere and that could alter atmospheric chemistry and potentially cool the planet.

The study said the presence of specific isotopes, such as iron-60 (60Fe) and plutonium-244 (244Pu), in geological records supports the theory.

The research report highlighted that the isotopes, typically associated with supernovas and neutron star mergers, might have been delivered by interstellar dust during such an encounter, thus previous attributions to nearby supernovas are now being reconsidered.

Lead author Merav Opher, a space physicist and expert on the heliosphere at Boston University, said in a statement: "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.

"But as soon as the Earth was away from the cold cloud, the heliosphere engulfed all the planets, including Earth."

The study indicated that the heliosphere's contraction during such events could last from hundreds of years to a million years, and we might face another similar encounter within the next million years.

"This work should be revisited with modern atmospheric modelling," the team suggested in the paper, noting: "It has been suggested that climate changes around this time could have affected human evolution. The hypothesis is that the emergence of our species Homo sapiens was shaped by the need to adapt to climate change. With the shrinkage of the heliosphere, the Earth was exposed directly to the ISM."

The study has sparked renewed interest in understanding how interstellar phenomena influence our planet, emphasizing the need for further research.