IR Detection of H 2O 2 at 80 K in Ion-Irradiated Laboratory Ices Relevant to Europa
Abstract
We present the first in situ laboratory detection of H 2O 2 in H + irradiated ices at temperatures relevant to the icy Galilean satellites. These experiments were motivated by the recent Galileo NIMS detection on Europa of a 3.5-μm band identified with H 2O 2 (R. W. Carlson et al. 1999, Science283, 2062-2064). In our laboratory experiments, the IR signature of H 2O 2 was easily observed after irradiation of pure H 2O at 16 K, but it was not seen after irradiation at 80 K. Radiolysis of mixtures of H 2O with O 2 or CO 2 at 80 K did produce H 2O 2. These results show that ices more complex than pure H 2O are involved in the radiolysis pathway to form H 2O 2 on Europa. We also report the intrinsic band strength and radiation yield of H 2O 2 in ice mixtures, along with possible formation and destruction mechanisms. Sufficient concentrations of H 2O 2 can be formed in H 2O ices containing O 2 to explain the NIMS observation.
- Publication:
-
Icarus
- Pub Date:
- May 2000
- DOI:
- 10.1006/icar.1999.6325
- Bibcode:
- 2000Icar..145..282M