Iridium, significant in the hypothesis of the icy Earth
2005/07/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria
The study of the iridium element reinforces the idea of the icy Earth that about 700 million years ago the ice completely covered the terrestrial surface.
This element comes from space to Earth, mostly in dust particles. On the terrestrial surface, normally the iridium is distributed uniformly in the rocky sediments. But in the sediments of 600 and 750 million years ago the iridium appears accumulated. Some geologists consider that this was not because in those times there were large amounts of dust coming from space, but that the earth's surface was covered with ice. The iridium remained in ice layers during those years, and when all the ice was melted, it would be stored in the sediments. Given the amount of iridium, geologists believe that the terrestrial surface was frozen for 12 million years. Geologists have found the last traces of the iridium accumulated in Congo and Zambia, meaning that at this latitude the Earth was also covered with ice.
The iridium study does not fully affirm the hypothesis of the icy Earth, but it seems to be a favorable data. Among other things, studies of several isotopes are missing and, despite this, geologists will not prove the hypothesis.
