A new study suggests that about two million years ago, the solar system passed through a dense molecular cloud that had a significant impact on Earth’s climate. An article published in the journal Nature Astronomy by astrophysicist Merav Ofer, of Boston University, and astronomer Avi Loeb, of Harvard University, reveals that this passage may have significantly reduced the amount of solar radiation reaching Earth, causing a period From extreme cold.
Two million years ago, Earth was a completely different place. Our early human ancestors lived alongside saber-toothed tigers, mastodons, and large rodents, in an extremely cold environment. This period of ice, which repeated regularly until about 12 thousand years ago, is due to several factors such as the planet’s tilt and rotation, tectonic movements, volcanic activity, and carbon dioxide levels. However, the new research suggests that extraterrestrial factors, such as the Sun’s position in the galaxy, also played a crucial role.
Ophir and Loeb’s research uses sophisticated computer models to go back in time and map the position of the Sun and the Solar System. The results suggest that two million years ago, the solar system passed through a cold, dense interstellar cloud, known as the local cold cloud belt. This cloud, composed mainly of hydrogen, would put pressure on the heliosphere – the plasma bubble that protects the solar system from cosmic radiation.
“When passing through this dense cloud, the heliosphere was compressed, leaving Earth and other planets in the solar system temporarily unprotected,” Over explained. This exposure to the interstellar medium allowed radioactive particles and cosmic rays to reach Earth, affecting its climate and environment.
Over and Loeb’s theory is supported by geological evidence. Isotopes of iron-60 and plutonium-244, which indicate highly radioactive events, have been found in ocean and lunar sediments, Antarctic snow and ice cores dating back to about 2 million years ago. This period coincides with temperature records that indicate significant cooling.
“Passing through the dense cloud could have obscured the heliosphere for hundreds of years to up to a million years,” Over explained. “But once the Sun moved away from the cloud, the heliosphere returned around all the planets, including Earth.”
This discovery suggests that the Sun’s position in the galaxy may have a greater impact on Earth’s climate history than previously thought. Avi Loeb highlights the importance of this research: “We have discovered that our cosmic neighborhood can significantly affect life on Earth. Our passage through dense gas clouds millions of years ago has exposed Earth to an increasing influx of cosmic rays and hydrogen atoms.
Scientists are now seeking to pinpoint the Sun’s position seven million years ago and even further, using data from the European Space Agency’s Gaia mission, which maps the location and path of more than a billion stars in the Milky Way.
Conclusion
“This is just the beginning,” Ofer says. The team hopes that this research will foster further exploration of how the solar system was affected by external forces in the past and how these influences helped shape life on Earth. Through this research, understanding of the interaction between Earth’s climate and cosmic events can be greatly deepened, opening new possibilities for climate science and astronomy.
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