Oldest ever known ice sample found in 2.7-mn-yr-old ice core
US researchers have retrieved a 2.7-million-year-old ice core from Antarctica, about 1.7 million years older than the oldest known sample which they recovered two years back. The team drilled 205 metres deep compared to their previous attempt of 128 metres. Further, the atmospheric CO2 levels then was inferred to be around 300 ppm, compared to today's 400 ppm.