Earth's "snowball" theory describes the complete glaciation of the Earth from 600 to 800 millions of years ago. To explain this cataclysm, Alexander Pavlov, of the University of Colorado Boulder, and his colleagues propose in Geophysical Research Letters a new hypothesis. The researchers suggest that less than a billion years ago, our solar system traversed, for a period of about 500 000 years, a moderately dense interstellar cloud that resulted in an increase in the flow of abnormal cosmic rays. or ACR (Anomalous Cosmic Ray).
These ACRs are ions, resulting from photoionization or charge exchanges on the neutral gases of the interstellar cloud and acceleration due to collisions that occur when they come out of the solar wind. However, according to the computer models of the authors of the study, increasing the flow of RTAs for a million years could have been enough to completely disrupt the Earth's stratosphere.
During this period, it is indeed possible that an inversion of the magnetic poles of the Earth has favored the atmospheric penetration of cosmic rays in greater quantities, which would have in turn contributed to form more nitrogen oxides (NOx ). Concentrations of these gases multiplied by 100 between 20 and 40 km altitude could have destroyed 40% of the protective layer of ozone (this figure climbing to 80% in the polar regions).
Therefore, the combination of low light due to the interstellar cloud and a very small ozone layer could explain a total glaciation of the Earth's surface. To validate this theory, the researchers will now focus on analyzing the 235 uranium levels in rocks of this distant time (the U235 is not naturally produced on Earth but is present in the stellar clouds).
LAT 05 / 03 / 05 (Massive cloud-May-have frozen the earth)