[1] Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada
[2] Univ Western Ontario, Ctr Planetary Sci & Explorat CPSX, London, ON N6A 3K7, Canada
[3] SETI Inst, 189 Bernardo Ave,Suite 100, Mountain View, CA 94043 USA
[4] Open Univ, Dept Phys Sci, Robert Hooke Bldg, Milton Keynes MK7 6AA, Bucks, England
[5] ACRI ST, 260 Route Pin Montard, F-06904 Sophia Antipolis, France
[6] WM Keck Observ, 65-1120 Mamalahoa Highway, Kamuela, HI 96743 USA
[7] NASA, Ames Res Ctr, USRA, Stratospher Observ Infrared Astron, MS N232-12, Moffett Field, CA 94035 USA