Earth's "snowball" theory describes the complete glaciation of the Earth from 600 to 800 million 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 went through, 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 RTAs are ions, resulting from photoionization or charge-exchange on neutral interstellar cloud of gas and subjected to acceleration as a result of collisions that occur when ortent the solar wind. Now, according to computer models of the authors of the study, the increased flow of RTAs for a million years would have been enough to upset the Earth's stratosphere altogether.
During this period, it is possible that a reversal of the magnetic poles of the Earth have favored atmospheric penetration of cosmic rays in greater quantities, rays which would in turn helped train more nitrogen oxides (NOx ). Concentrations of these gases increased by between 100 20 and 40 km altitude could destroy 40% of the protective ozone layer (this figure climbing to 80% in the polar regions).
Therefore, the combination of low brightness due to interstellar cloud and a greatly reduced ozone layer could explain a total glaciation of the Earth's surface. To confirm this theory, researchers will now focus on analyzing 235 levels of uranium in rocks of that distant time (the U235 is not produced naturally on Earth but is present in stellar clouds).
LAT 05 / 03 / 05 (Massive cloud-May-have frozen the earth)