The goal of this study is to quantify uptake of H2O and HNO3 by and estimate their residence time on alumina particles in Athena-2 rocket plumes. This study uses in situ measurements made in the lower stratosphere with the NASA WB-57F high-altitude aircraft on 24 September 1999. Constraining the Atmospheric and Environmental Research, Inc. (AER), plume model with available measurements, we found that (1) H2O uptake coefficient for alumina particles is larger than 3 ¿ 10-4, (2) HNO3 is produced via ClONO2 + HCl → Cl2 + HNO3 on alumina particles and resides on their surfaces for 5--52 min, and (3) alumina particles in the plume are covered by 100--200 monolayers of adsorbed H2O and 0.1--10 monolayers of HNO3 under lower stratospheric conditions. These values are uncertain by at least a factor of 2. We speculate that the H2O coverage remaining on alumina particles accelerates the ClONO2 + HCl → Cl2 + HNO3 reaction, thus leading to a larger than previously thought global ozone loss to solid-fueled rocket emissions, especially if at least several percent of emitted alumina mass are in submicron particles.