The infrared spectrum of Neptune at 3.5–4.1 microns: Search for H$\mathsf{_{3}^{+}}$ and evidence for recent meteorological 
 variations

Feuchtgruber, H.; Encrenaz, Th.

doi:10.1051/0004-6361:20030414

Cited by 11 publications

(24 citation statements)

References 21 publications

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“…5.3). Long-term variations by a factor of two in the L band have been observed already in the past (Feuchtgruber & Encrenaz 2003).…”

Section: Observationsmentioning

confidence: 96%

“…Spatially resolved spectroscopy of CO and other O-bearing species would provide invaluable clues to understand the stratospheric CO abundance. Feuchtgruber & Encrenaz (2003) measured the spectrum of Neptune in August 2002 in the L-band (3.5-4.1 μm) with the ISAAC imaging spectrometer at the ANTU of the Very Large Telescope at the European Southern Observatory in Cerro Paranal. They found the observed flux to be stronger by a factor of three compared to measurements at the same wavelength recorded in 1997, five years earlier, and attributed the excess of infrared flux to an increased production of photochemical aerosols.…”

Section: Atmospheric Compositionmentioning

confidence: 99%

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Neptune's atmospheric composition from AKARI infrared spectroscopy

Fletcher

Drossart

Burgdorf

et al. 2010

A&A

115

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Aims. Disk-averaged infrared spectra of Neptune between 1.8 and 13 μm, obtained by the AKARI infrared camera (IRC) in May 2007, have been analysed to (a) determine the globally-averaged stratospheric temperature structure; (b) derive the abundances of stratospheric hydrocarbons; and (c) detect fluorescent emission from CO at 4.7 μm. Methods. Mid-infrared spectra (SG1 and SG2 channels of AKARI/IRC), with spectral resolutions of 47 and 34 respectively, were modelled using a line-by-line radiative transfer code to determine the temperature structure between 1-1000 μbar and the abundances of CH 4 , CH 3 D and higher-order hydrocarbons. A full non-LTE radiative model was then used to determine the best fitting CO profile to reproduce the fluorescent emission observed at 4.7 μm in the NG channel (with a spectral resolution of 135). Results. The globally-averaged stratospheric temperature structure is quasi-isothermal between 1-1000 μbar, which suggests little variation in global stratospheric conditions since studies by the Infrared Space Observatory a decade earlier. The derived CH 4 mole fraction of (9.0 ± 3.0) × 10 −4 at 50 mbar, decreasing to (0.9 ± 0.3) × 10 −4 at 1 μbar, is larger than that expected if the tropopause at 56 K acts as an efficient cold trap, but consistent with the hypothesis that CH 4 leaking through the warm south polar tropopause (62-66 K) is globally redistributed by stratospheric motion. The ratio of D/H in CH 4 of 3.0 ± 1.0 × 10 −4 supports the conclusion that Neptune is enriched in deuterium relative to the other giant planets. We determine a mole fraction of ethane of (8.5 ± 2.1) × 10 −7 at 0.3 mbar, consistent with previous studies, and a mole fraction of ethylene of 5.0 +1.8 −2.1 × 10 −7 at 2.8 μbar. An emission peak at 4.7 μm is interpreted as a fluorescent emission of CO, and requires a vertical distribution with both external and internal sources of CO. Finally, comparisons to previous L-band studies indicate significant variability of Neptune's flux densities in the 3.5-4.1 μm range, related to changes in solar energy deposition.

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“…5.3). Long-term variations by a factor of two in the L band have been observed already in the past (Feuchtgruber & Encrenaz 2003).…”

Section: Observationsmentioning

confidence: 96%

Section: Atmospheric Compositionmentioning

confidence: 99%

Neptune's atmospheric composition from AKARI infrared spectroscopy

Fletcher

Drossart

Burgdorf

et al. 2010

A&A

115

View full text Add to dashboard Cite

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“…This was evident in visible images taken during the 1989 flyby of Neptune by the Voyager 2 spacecraft (Smith et al 1989) and in subsequent earth-based imaging (Sromovsky et al 2002;Max et al 2003;Feuchtgruber & Encrenaz 2003). Valuable information on dynamical and radiative processes in Neptune's atmosphere can also be gained from measurements of its temperature field.…”

Section: Observationsmentioning

confidence: 96%

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

Orton

Encrenaz²,

Leyrat

et al. 2007

A&A

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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 result from a localized wave propagating upward from the troposphere.

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“…All reported attempts at detecting H + 3 emission from Neptune have been unsuccessful (Trafton et al 1993; Encrenaz et al 2000; Feuchtgruber & Encrenaz 2003). The United Kingdom Infrared Telescope (UKIRT) observations of Trafton et al (1993) derived an upper limit to the H + 3 Q branch discrete single line emission flux of 5 × 10 −18 W m −2 , equating to an upper limit of the H + 3 column density of a few ×10 14 m −2 , assuming a temperature of 550 K. Feuchtgruber & Encrenaz (2003) derived an upper limit on the density of 2.9 × 10 14 m −2 using observations with the Very Large Telescope (VLT), assuming a temperature of 550 K. Both of these density limits are about an order of magnitude smaller than the column densities observed at Uranus and about 2 orders smaller than those observed at Jupiter.…”

Section: Introductionmentioning

confidence: 99%

“…The model of Lyons (1995) predicts a H + 3 peak density of 250 cm −3 at an altitude of about 1350 km above the 1 bar level, giving a column‐integrated density of 4 –5 × 10 13 m −2 (Feuchtgruber & Encrenaz 2003).…”

Section: Introductionmentioning

confidence: 99%

New limits on H+3 abundance on Neptune using Keck NIRSPEC

Melin

Stallard

Miller

et al. 2010

Monthly Notices of the Royal Astronomical Society

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Neptune and Uranus are observed with Keck II NIRSPEC in an attempt to detect H+3 emission from Neptune. In this set of observations, H+3 emission remains undetected at Neptune, whereas line‐resolved emission from Uranus was observed with a signal‐to‐noise ratio of ∼100. Using this, we have derived an upper limit of the column‐integrated H+3 density on Neptune of 1.5 (+4.8−0.9)× 1013 m−2, assuming a temperature of 550±100 K. This value improves the previous established limit by a factor of 20 and shows that the H+3 density predicted by the best available model overestimate the density by at least a factor of 3. In addition, the solar reflection continuum of Neptune in the K and L′ bands is seen to be brighter on the Northern hemisphere by a factor of ∼2, whereas previous observations had noted the solar reflection as being brighter on the Southern hemisphere.

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The infrared spectrum of Neptune at 3.5–4.1 microns: Search for H$\mathsf{_{3}^{+}}$ and evidence for recent meteorological variations

Cited by 11 publications

References 21 publications

Neptune's atmospheric composition from AKARI infrared spectroscopy

Neptune's atmospheric composition from AKARI infrared spectroscopy

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

New limits on H+3 abundance on Neptune using Keck NIRSPEC

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