Evidence for methane escape and strong seasonal and dynamical perturbations of Neptune's atmospheric temperatures

Aims. We studied the distribution of mid-infrared thermal emission from Neptune to determine the spatial variability of temperatures and the distribution of trace constituents, allowing us to determine the relative strengths of radiation and dynamics in its atmosphere. Methods. Mid-infrared images of the planet were taken at the Very Large Telescope on 1–2 September 2006. Results. These images reveal strong inhomogeneities in thermal emission. 17.6 and 18.7-µm images exhibit strong seasonally elevated south polar temperatures near Neptune’s tropopause. These high temperatures allow tropospheric methane, elsewhere cold-trapped at depth, to escape into the stratosphere. Poleward of 70 ◦ S, 8.6- and 12.3-µm emission from stratospheric methane and ethane is enhanced, and a distinct, warm stratospheric feature near 65–70 ◦ S latitude is rotating with the neutral atmosphere. This feature may

[1]  H. Hammel,et al.  Distribution of Ethane and Methane Emission on Neptune , 2006 .

[2]  A. Warn-Varnas,et al.  Yellow Sea ocean-acoustic solitary wave modeling studies , 2005 .

[3]  G. Orton,et al.  Saturn's Temperature Field from High-Resolution Middle-Infrared Imaging , 2005, Science.

[4]  E. Lellouch,et al.  A dual origin for Neptune's carbon monoxide? , 2005 .

[5]  T. Encrenaz,et al.  The infrared spectrum of Neptune at 3.5-4.1 microns: Search for H3+and evidence for recent meteorological variations , 2003 .

[6]  D. S. Acton,et al.  Cloud Structures on Neptune Observed with Keck Telescope Adaptive Optics , 2003 .

[7]  H. Hammel,et al.  A prominent apparition of Neptune's South Polar feature , 2002 .

[8]  K. Baines,et al.  The Unusual Dynamics of Northern Dark Spots on Neptune , 2002 .

[9]  P. Gierasch,et al.  Thermal Structure and Para Hydrogen Fraction on the Outer Planets from Voyager IRIS Measurements , 1998 .

[10]  D. Hunten,et al.  Collision of comet Shoemaker-Levy 9 with Jupiter observed by the NASA infrared telescope facility , 1995, Science.

[11]  H. Hammel,et al.  Clouds, hazes, and the stratospheric methane abundance in Neptune. , 1994, Icarus.

[12]  S. Limaye,et al.  Dynamics of Neptune's Major Cloud Features , 1993 .

[13]  William E. Blass,et al.  Thermal spectroscopy of Neptune: the stratospheric temperature, hydrocarbon abundances, and isotopic ratios , 1992 .

[14]  Glenn S. Orton,et al.  The quasiquadrennial oscillation of Jupiter's equatorial stratosphere , 1991, Nature.

[15]  S. Limaye,et al.  Winds of Neptune - Voyager observations of cloud motions , 1991 .

[16]  B. Bézard,et al.  Hydrocarbons in Neptune's stratosphere from Voyager infrared observations , 1991 .

[17]  R. Baron,et al.  Thermal Maps of Jupiter: Spatial Organization and Time Dependence of Stratospheric Temperatures, 1980 to 1990 , 1991, Science.

[18]  R. West,et al.  Calibration of the 7- to 14-μm brightness spectra of Uranus and Neptune , 1990 .

[19]  S. K. Croft,et al.  Voyager 2 at Neptune: Imaging Science Results , 1989, Science.

[20]  J. Ely,et al.  Thermophysical Properties of Fluids. II. Methane, Ethane, Propane, Isobutane, and Normal Butane , 1987 .

[21]  G. Orton,et al.  The spectra of Uranus and Neptune at 8-14 and 17-23 microns , 1987 .