Vapor Pressure Isotope Fractionation Effects in Planetary Atmospheres: Application to Deuterium

✍ Scribed by Thierry Fouchet; Emmanuel Lellouch

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 175 KB
• Volume: 144
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.1999.6264

✦ Synopsis

The impact of the vapor pressure difference between deuterated and nondeuterated condensing molecules in planetary atmospheres is quantitatively assessed. This difference results in a loss of deuterium in the vapor phase above the condensation level. In Titan, Uranus, and Neptune, the effect on CH 3 D is too subtle to alter current D/H ratio determinations. In Mars, the effect can induce a large depletion of HDO, starting about one scale height above the condensation level. Although the current infrared measurements of the D/H ratio appear to be almost unaffected, the intensity of diskaveraged millimetric HDO lines can be modified by about 10%. The effect is much stronger in limb sounding and can be easily detected from orbiter observations.