Mammoths, saber-toothed tigers, enormous rodents, endless glaciers. About two million years ago, Earth was a very different place than we know it today. During this period, a series took place Glaciers — lasting millions of years and continuing until about 12,000 years ago — completely changed the environment, making it hostile to any form of life. Experts in Paleoclimatology Over the years, various hypotheses have been proposed that could have caused the transition of ice ages on our planet: the greenhouse effect, the tilt and rotation of the Earth, the movement of tectonic plates, volcanic eruptions. What if such drastic changes were caused not only by the Earth, but also by the Sun's position in the galaxy?
For a brief period, millions of years ago, Earth may have been excluded from the Sun's protective plasma shield, the heliosphere, depicted here as a dark gray blob against the background of interstellar space. According to new research, this may have exposed the Earth to high levels of radiation and affected the climate. Credit: Ofer, et al., Natural Astronomy
According to A study It was published this week Natural Astronomy And led by Boston University researchers, our solar system may have experienced a denser, cooler. Interstellar cloud About two million years ago. This may interfere with the solar wind and temporarily slow it downHeliosphereA protective shield of plasma from the sun surrounds our solar system.
A dangerous encounter that could change Earth's climate. Made up of a steady stream of charged particles, the solar wind, which extends beyond Pluto, the heliosphere is actually a kind of giant bubble that's filled with cosmic radiation and interstellar rays — rays that can mutate DNA. This type of protection is considered to be one of the main reasons for life on Earth.
Big ones on the other hand Interstellar gas cloudsUp to a million times the mass of the Sun and extremely cold, from tens to a few hundred degrees below absolute zero.
According to the research team, a dense cold interstellar cloud may have “shrinked” the heliosphere, temporarily exposing Earth and other planets in the Solar System to high levels of cosmic radiation. “Our study is the first to quantitatively demonstrate that something outside the Sun and the Solar System may have influenced Earth's climate,” he says. Merao Ober, an astrophysicist at Boston University and lead author of the research. “Stars move, and this work shows not only that they move, but that they undergo drastic changes.”
The research team examines how the heliosphere, and the region the Sun moves through space, can affect Earth's atmospheric chemistry. Using sophisticated computer models, he looked back in time and reconstructed the position of the Sun — along with the heliosphere and the rest of the Solar System — two million years ago. The researchers mapped the path of the Local Ribbon of Cold Clouds, a system of dense, cold stellar clouds composed mainly of hydrogen atoms: simulations suggested that one of these clouds – the so-called Local Lynx – is a cold cloud in the Lynx constellation. It probably interacted with the heliosphere 2-3 million years ago.
If this had happened, the Earth would have emerged as a mixture of gas, dust, nuclear elements from exploded stars – including iron and plutonium – and radioactive particles that the heliosphere normally filters out. Without its shielding, such particles could have reached Earth. There is no shortage of evidence that this may actually have happened: geological evidence, in fact, shows an increase in iron-60 isotopes of plutonium-244 in the oceans, Antarctic ice and ice sheets during the same period. , as well as on the Moon. Also, the isotopes are consistent with temperature records indicating a period of significant cooling. One hypothesis is that there may be a connection between the local lynx of the cold cloud and the interaction of our planet. Massive Quaternary glaciers.
A cool interstellar molecular cloud, seen with the Webb Space Telescope. Credits: NASA, ESA, CSA and M. Jamani (ESA)
This research not only sheds new light on Earth's geological and climatic past, but highlights the importance of cosmic dynamics in shaping our planet's climate conditions. “Our 'cosmic neighbors' beyond the solar system rarely affect life on Earth,” he says Avi Loeb, director of the Institute for Theory and Computation at Harvard University and co-author of the work. “It is exciting to discover that our passage through dense clouds a few million years ago may have exposed Earth to a very large stream of cosmic rays and hydrogen atoms. Our findings open a new window on the relationship between the evolution of life on Earth and our cosmic environment.”
According to Ofer, the outward pressure exerted by the interstellar cold cloud in the Lynx could have contracted the heliosphere for hundreds of years or even a million years. Then, once the Earth moved away from the cloud, the heliosphere resumed its “protective” role.
Although we do not know the exact effect this cold cloud had on Earth's climate, it is possible that the Solar System encountered other interstellar cold clouds over the billions of years that it formed. In the future, we will meet more of them in about a million years.
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