Privileged Planet: the effect of interstellar clouds (Introduction)

by David Turell , Tuesday, June 11, 2024, 20:34 (97 days ago) @ David Turell

A brief loss of the sun's protection:

https://www.sciencedaily.com/releases/2024/06/240610140249.htm

"Scientists theorize that ice ages occur for a number of reasons, including the planet's tilt and rotation, shifting plate tectonics, volcanic eruptions, and carbon dioxide levels in the atmosphere. But what if drastic changes like these are not only a result of Earth's environment, but also the sun's location in the galaxy?

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"...found evidence that some two million years ago, the solar system encountered an interstellar cloud so dense that it could have interfered with the sun's solar wind. Opher and her co-authors believe this shows that the sun's location in space might shape Earth's history more than previously considered.

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"Our whole solar system is swathed in a protective plasma shield that emanates from the sun, known as the heliosphere. It's made from a constant flow of charged particles, called solar wind, that stretch well past Pluto, wrapping the planets in what NASA calls a "a giant bubble." It protects us from radiation and galactic rays that could alter DNA, and scientists believe it's part of the reason life evolved on Earth as it did. According to the latest paper, the cold cloud compressed the heliosphere in such a way that it briefly placed Earth and the other planets in the solar system outside of the heliosphere's influence.

"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," says Opher, who is an expert on the heliosphere. Her models have quite literally shaped our scientific understanding of the heliosphere, and how the bubble is structured by the solar wind pushing up against the interstellar medium -- which is the space in between stars and beyond the heliosphere in our galaxy. Her theory is that the heliosphere is shaped like a puffy croissant, an idea that shook the space physics community. Now, she's shedding new light on how the heliosphere, and where the sun moves through space, could affect Earth's atmospheric chemistry.

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"...If that had happened, says Opher, Earth would have been fully exposed to the interstellar medium, where gas and dust mix with the leftover atomic elements of exploded stars, including iron and plutonium. Normally, the heliosphere filters out most of these radioactive particles. But without protection, they can easily reach Earth. According to the paper, this aligns with geological evidence that shows increased 60Fe (iron 60) and 244Pu (plutonium 244) isotopes in the ocean, on the moon, Antarctic snow, and ice cores from the same time period. The timing also matches with temperature records that indicate a cooling period.

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"The outside pressure from the Local Lynx of Cold Cloud could have continually blocked out the heliosphere for a couple of hundred years to a million years, Opher says -- depending on the size of the cloud. "But as soon as the Earth was away from the cold cloud, the heliosphere engulfed all the planets, including Earth," she says. And that's how it is today.

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"This is only the beginning," Opher says. She hopes that this paper will open the door to much more exploration of how the solar system was influenced by outside forces in the deep past and how these forces have in turn shaped life on our planet."

Comment: if is amazing how many precise events occurred to shape our Earth as it now is. I doubt it is all contingent chance.