1. Department of Earth and Atmospheric Sciences; University of Alberta; Edmonton Alberta T6G 2R3 Canada
2. Solar System Exploration Division, Code 691; NASA Goddard Space Flight Center; Greenbelt Maryland 20771 USA
3. NASA Postdoctoral Program at NASA Goddard Space Flight Center; Greenbelt Maryland 20771 USA
4. Department of Chemistry; Catholic University of America; Washington DC 20064 USA
5. Department of Physical Sciences; MacEwan University; Edmonton Alberta T6G 2R3 Canada