The detection of a layer of massive negative ions (masses up to 400 u and above) by means of rocket borne quadrupole mass spectrometry in the polar summer mesopause region is reported. Taking into account the geophysical and atmospheric conditions encountered during the measurement different possible explanations for these ions are evaluated. We arrive at the conclusion that they are best explained as being the negatively charged fraction of the so called meteor smoke particles. ¿ American Geophysical Union 1992