A NASA Ames ER-2 aircraft encountered polar stratospheric cloud particles on July 28 and July 30, 1994 during the ASHOE/MAESA deployment. Stratospheric particles were collected by impaction techniques on specially treated substrates. For the first time, Nitron-nitrate reaction spots were detected on the ice crystal replicas, indicating the presence of NO3- ions on/in ice. Because the reaction spots were detected only on very small crystals (r<1 &mgr;m) and never on larger crystals, suggest that the amount of NO3- coating sufficient to initiate reactions will accumulate during ice crystal evaporation in ice subsaturated air. This may slow down the evaporation rate and enable ice crystals to survive longer in subsaturated environment. That provides an explanation of why on both days ice crystals were replicated at temperatures above the frost point, when their appearance and size suggest substantial evaporation.¿ 1997 American Geophysical Union