Evidence for a Low Surface Temperature on Pluto from Millimeter-Wave Thermal Emission Measurements

• Published in: Science (American Association for the Advancement of Science) 1993-09, Vol.261 (5129), p.1713-1716
• Main Authors: Stern, S. Alan, Weintraub, David A., Festou, Michel C.
• Format: Article
• Language: English
• Subjects: Albedo; Artificial satellites; Astronomy; Data ranges; Earth, ocean, space; Emissivity; Exact sciences and technology; Flux density; Methane; Observations; Occultation; Planetary meteorology; Planets, their satellites and rings. Asteroids; Pluto; Pluto (Dwarf planet); Pluto (Planet); Solar system; Surface temperature; Wavelengths
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.261.5129.1713

Thermal continuum emission from the Pluto-Charon system has been detected at wavelengths of 800 and 1300 microrneters, and significant upper limits have been obtained at 450 and 1100 micrometers. After the subtraction of emission from Charon, the deduced surface temperature of much of Pluto is between 30 and 44 kelvin, probably near 35 to 37 kelvin. This range is significantly cooler than what radiative equilibrium models have suggested and cooler than the surface temperature derived by the Infrared Astronomy Satellite. The low temperature indicates that methane cannot be present at the microbar pressure levels indicated by the 1988 stellar occultation measurements and that the methane features in Pluto's spectrum are from solid, not gas-phase, absorptions. This result is evidence that Pluto's atmosphere is dominated by nitrogen or carbon monoxide rather than methane.