15 September 2000
Vol 289, Issue 5486

About The Cover

Cover image expansion

COVER A record of the 100,000-year ice-age cycle is preserved in the oxygen isotopic composition of calcium carbonate made by deep-sea foraminifera. This record is reinterpreted by comparing it to the isotopic composition of atmospheric O2 extracted from ice cores from Vostok, Antarctica. The comparison suggests that variations of Earth's orbital eccentricity drive the glacial cycles by influencing atmospheric CO2 levels. See page 1897. [Image: NASA Goddard Space Flight Center/Scientific Visualization Studio]