The solar system crossed an interstellar cloud two million years ago so dense and so cold that it altered the climate on Earth, a finding that shows that the location of the Sun in space could influence Earth’s history much more than previously believed. until now.
It has been verified by an international team of researchers, led by astrophysicist Merav Opher, professor of astronomy at Boston University and member of the Radcliffe Institute at Harvard, and the results of their work are published in Nature Astronomy.
Two million years ago, the Earth was a very different place, where human ancestors coexisted with saber-toothed tigers, mastodons and enormous rodents, and the planet had fallen into a deep freeze, with multiple ice ages that followed one another. until about 12,000 years ago.
Scientists have theorized about the reasons for ice ages, such as the planet’s tilt and rotation, changes in plate tectonics, volcanic eruptions or carbon dioxide levels in the atmosphere, but the new work suggests that these drastic changes do not occur. They are only due to the Earth’s environment, also to the position of the Sun in the galaxy.
Scientists have found evidence that about two million years ago the solar system encountered an interstellar cloud so dense that it could have interfered with the solar wind.
The protective shield
The solar system is enveloped in a protective shield of plasma emanating from the sun, known as the heliosphere, formed by a constant flow of charged particles, called the solar wind, that extend beyond Pluto and envelop the planets in what they are. called “a giant bubble.”
That bubble protects Earth from radiation and galactic rays that could alter DNA, and scientists believe that is partly the reason why life evolved on Earth as it did, and according to the work published this Monday the Cold cloud compressed the heliosphere in such a way that it briefly placed Earth and the other planets in the solar system outside the influence of the heliosphere.
“This work is the first to demonstrate that there was an encounter between the Sun and something outside the solar system that would have affected the Earth’s climate,” says Opher, an expert in the heliosphere, in the same scientific publication.
To study this phenomenon, Opher and his collaborators “looked” back in time, using sophisticated computer models to visualize the position of the Sun two million years ago, and with it the position of the heliosphere and the rest of the solar system.
They also traced the trajectory of the “Local Cold Cloud Belt” system, a chain of large, dense, very cold clouds composed mostly of hydrogen atoms, and their simulations showed that one of the clouds near the end of that ribbon could have collided with the heliosphere.
The solar system will cross clouds like this again
If that happened like this, Opher maintains, Earth would have been completely exposed to the interstellar medium, where gas and dust mix with atomic elements left over from exploded stars, including iron and plutonium.
Normally, the heliosphere filters out most of these radioactive particles, but without protection they can easily reach Earth, and according to researchers this is consistent with geological evidence showing an increase in some isotopes in the ocean, on the Moon, in the snow from Antarctica and in ice cores from the same time period.
It’s impossible to know the exact effect the cold clouds had on Earth, or whether they might have sparked an ice age, but scientists do know that there are at least a couple more cold clouds in the interstellar medium that the Sun has likely encountered in the past. the billions of years since its birth, and that it is likely to stumble upon more in a million or so years.
Determining the location of the Sun millions of years ago, as well as the cold cloud system, is becoming possible thanks to data collected by the European Space Agency’s Gaia mission, which is building the largest three-dimensional map of the galaxy and offering a vision unprecedented speed at which stars move.
FEW (EFE, Nature Astronomy)
