The Arctic summer mesopause at ~88 km is the coldest-known place (~130 K) in the terrestrial atmosphere and is ~60 K colder in summer than winter. Indirect evidence has suggested that the summer mesopause temperatures in the Antarctic are a few Kelvin warmer than in the Arctic. However, reliable measurements have not been available at southern high latitudes to verify this. We report the very first in situ temperature observations in the summer mesosphere from Antarctica based on rocket-borne falling spheres launched from Rothera (68¿S, 68¿W). The first of 24 successful launches, on 5 January 1998, showed a mesopause temperature of 129 K at 87 km, surprisingly close to northern hemisphere (NH) mean summer values. During January the mesospheric temperatures are similar to the northern summer, but the difference increases to several Kelvin in February. ¿ 1999 American Geophysical Union