Results of apparent atomic oxygen reactions on Ag, C, and Os exposed during the Shuttle STS‐4 orbits

Films selected for anticipated reaction with atomic oxygen, namely carbon, silver, and osmium, were exposed during the Shuttle STS‐4 mission. A silver film 225 ± 5 nm thick was converted to a transparent blue‐green interference film 355 ± 5 nm thick. Both carbon and osmium films 10‐30 nm thick apparently formed volatile oxides and disappeared, except where well shielded. A calculated total of approximately 7 × 10 19 oxygen atoms per cm² struck the surfaces, which could have removed on the order of 3 µm of material if only 10% reacted. The absence of apparent effects on adjacent thin and thick gold films is offered as evidence that sputtering is not responsible.