Research suggests role of interstellar cloud in recent ice ages

Over the past two million years, Earth has endured several ice ages, including giant sloths, saber-toothed tigers, woolly mammoths, and early human ancestors. While the causes of these ice ages are still unknown, new research suggests that exposure to gas between Earth’s colder, denser clouds may be the cause.

Boston University (BU) and Harvard Ratcliffe Institute (HRI) researchers have published new research on natural astronomy that uses data from the European Space Agency’s Gaia satellite to track the movement of the Solar System through the galaxy over the past 2 years. For up to 3 million years, the Sun’s heliosphere appears to have been in direct contact with a dense cloud of interstellar gas known as the Local Lynx of Cold Cloud (LLCC).

The heliosphere is an envelope of charged particles emanating from the Sun’s solar wind, which is pushed in front of the Solar System like waves from the bow of a ship on water. The heliosphere, which extends beyond Pluto and the Kuiper Belt, can be considered the boundary of the solar system beyond the stars.

According to the new study’s lead author, BU astronomy professor Merav Opher, when the heliosphere and LLCC met, the LLCC pushed the heliosphere back into the interior of the Solar System, effectively exposing Earth to the extreme cold of interstellar space.

„This paper is the first to show that there was an encounter between the Sun and something outside the Solar System that might have affected Earth’s climate,” Opher said. University Report. „Stars are moving, and now this paper shows not only that they are moving, but that they are undergoing drastic changes.”

Let’s look back in time to chart the Sun’s path through the galaxy

Using sophisticated computer models to monitor the state of the Solar System about 2 million years ago, Ober and his colleagues found that the Solar System passed very close to the Local Ribbon of Cold Clouds, a long strand of very cold clouds of hydrogen. In which LLCC. If the solar system came into contact with the LLCC, the consequences would have been dire for Earth’s inhabitants at the time.

According to Ofer, Earth may have lost the protection of the heliosphere and been fully exposed to interstellar space—a mixture of gas and dust and the nuclear remnants of long-exploded stars, including radioactive iron and plutonium.

Without the protection of the heliosphere, these elements and others can travel more easily to Earth, and according to the study, there is evidence of simultaneous increases in the isotopes iron 60 and plutonium 244 in the geological record. An era coinciding with a cooling period in Earth’s recent history.

„Our cosmic environment beyond the solar system rarely affects life on Earth,” said Avi Loeb, co-author of the paper and director of Harvard University’s Institute for Theory and Computation. „It is exciting to discover that our passage through dense clouds a few million years ago may have exposed Earth to a very large flux of cosmic rays and hydrogen atoms. Our results open a new window into the relationship between the evolution of life on Earth and our cosmic environment.

According to the study authors, it is not clear how long Earth has been outside the heliopause. Depending on the size of the cloud in contact with the solar system, this can range from several hundred to a million years. But Loeb said that once that interaction had passed, the heliopause would have bounced back.

The findings suggest that this isn’t the first contact the Solar System has had with interstellar cold clouds, and it won’t be our last.

Ofer hopes this new research will unlock more insights into how our solar system was attacked from outside and the evolution and development of life on Earth. „This is just the beginning,” he said.