title: Titan's 5 micrometers spectral window:  carbon monoxide and the albedo of the surface.
abstract: We have measured the spectrum of Titan near 5 micrometers and have found it to be dominated by absorption from the carbon monoxide 1-0 vibration-rotation band. The position of the band edge allows us to constrain the abundance of CO in the atmosphere and/or the location of the reflecting layer in the atmosphere. In the most likely case, 5 micrometers radiation is reflected from the surface and the mole fraction of CO in the atmosphere is qCO=10(+10/-5) ppm, significantly lower than previous estimates for tropospheric CO. The albedo of the reflecting layer is approximately 0.07(+0.02/-0.01) in the 5 micrometers continuum outside the CO band. The 5 micrometers albedo is consistent with a surface of mixed ice and silicates similar to the icy Galilean satellites. Organic solids formed in simulated Titan conditions can also produce similar albedos at 5 micrometers.
authors.affiliation: Space Telescope Science Institute, Baltimore, Maryland 21218, USA.  noll@stsci.edu
authors.forename: K S
authors.initials: KS
authors.lastname: Noll
authors.forename: T R
authors.initials: TR
authors.lastname: Geballe
authors.forename: R F
authors.initials: RF
authors.lastname: Knacke
authors.forename: Y J
authors.initials: YJ
authors.lastname: Pendleton
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D001272:Atmosphere / Q000032:analysis*; D002248:Carbon Monoxide; D005118:Extraterrestrial Environment; D010783:Photometry; D018539:Saturn; D013057:Spectrum Analysis
chemical_list: D002248:Carbon Monoxide