Á¦ ¸ñ    nBfJVMtOdGN ÀÌ ¸§    Trenton ³¯ Â¥    2018/06/28 Á¶ ȸ    1 Hold the line, please what do prescription drugs cost on the street The tale of Earthâ?™s oxidization is often told like this: For the first two billion years of Earthâ?™s existence, the mottled, volcano-pocked planet had little oxygen â?“ about 0.00001 percent of current levels. But, about 2.3 billion years ago, there was a dramatic change. In what was perhaps the happiest moment in Earthâ?™s existence, photosynthesizing bacteria enjoying the sunlight began, in an unusually productive feat for sunbathers, to process it into oxygen.