The Pleistocene epoch—with its glaciers, woolly mammoths, and Neanderthals—still looms large in Earth’s rearview mirror, ending just 12,000 years ago. Now, a team of researchers hypothesizes that those hundreds of thousands of years of our planet’s history may have been cool because of a cloud in space that briefly brought Earth out of the safety of the Sun’s warm glow.
Researchers theorize that about two million years ago, an interstellar cloud encroached upon the solar system in such a way that Earth and other planets were briefly outside the solar system. the heliosphere, a bubble of charged particles from our host star that today forms an amorphous envelope around the system. Their research was published today in natural astronomy.
“This paper is the first to quantitatively show that there has been an encounter between the Sun and something outside the solar system that would affect Earth’s climate,” Merav Opher, an astrophysicist at Boston University and lead author of the study, said in an email. to Gizmodo. Opher added that the team is “still trying to quantify this with modern climate models,” but with the increase in hydrogen and dust, “the Earth would enter an ice age.”
Opher’s team modeled data from HI4PI survey and found that our solar system may have passed through the Local Ribbon of Cool Clouds in the constellation Lynx 2 million to 3 million years ago. The Pleistocene began about 2.6 million years ago. It’s impossible to say for sure whether such cold clouds could have catalyzed an ice age, the publication noted, but further evidence that clouds manipulate the heliosphere may shed light on the kind of effects it would have on Earth.
The team’s model revealed that in such a passage, the heliosphere that surrounds Earth and its neighboring planets would shrink to about 0.22 AU, or less than a quarter the size of Earth’s distance from the Sun. To put it into perspective, ESA estimates that the closest boundary of today’s heliosphere is about 100 AU from the Sun, about twice as far as the Kuiper Belt.
Outside the heliosphere, Earth would be exposed to iron and plutonium in the interstellar medium, the team hypothesized. Their timeline is consistent with increases in plutonium-244 and iron-60, two isotopes of the respective elements known to occur from events in space, Antarctic snow, deep-sea sediments and lunar samples. And as Opher added, samples from Mars, if tested in the same way as lunar and Earth samples, could reveal a similar peak in the iron isotope about 2 to 3 million years ago.
At Boston University, Opher said the heliosphere could have been blocked anywhere from just a few hundred years to a million years. release. As the Earth and other planets moved away from the cloud, the heliosphere returned.
To verify their results, the team is now trying to determine the position of the Sun some seven million years ago, where there is evidence for another peak in the ratios of plutonium-244 and iron-60 in Earth’s ice and sediments. They’re trying to create a digital twin — essentially a high-tech model — of the heliosphere to better model the kinds of conditions our solar system might have been exposed to. Finally, additional data from ESA’s Gaia mission could further help the team determine the exact position of the Sun at any given moment in the distant past.
At least according to the Utah Geological Survey there have been five great ice ages on Earth. The first appeared more than 2 billion years ago, and the most recent began about 3 million years ago. According to NASA, ice ages can begin as a result of a combination of factors, including changes in Earth’s orbit, low amounts of energy from the Sun, the composition of the atmosphere, changes in ocean currents, and even volcanoes that were responsible for year without summer. In other words, we don’t want theories explaining Earth’s various cold moments, and the jury is out on exactly how an Earth outside the heliosphere could have catalyzed such a frigid period.
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