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Juno Jupiter image

Prof. Patrick Irwin

Professor of Planetary Physics

Research theme

  • Exoplanets and planetary physics

Sub department

  • Atmospheric, Oceanic and Planetary Physics

Research groups

  • Exoplanet atmospheres
  • Planetary atmosphere observation analysis
  • Solar system
patrick.irwin@physics.ox.ac.uk
Telephone: 01865 (2)72083
Atmospheric Physics Clarendon Laboratory, room 306
Personal research page
NEMESIS
  • About
  • Publications

Constraining the atmosphere of GJ 1214b using an optimal estimation technique

(2013)

Authors:

Joanna K Barstow, Suzanne Aigrain, Patrick GJ Irwin, Leigh N Fletcher, Jae-Min Lee
More details from the publisher

Upper limits for PH3 and H2S in Titan's atmosphere from Cassini CIRS

Icarus 224:1 (2013) 253-256

Authors:

CA Nixon, NA Teanby, PGJ Irwin, SM Hörst

Abstract:

We have searched for the presence of simple P and S-bearing molecules in Titan's atmosphere, by looking for the characteristic signatures of phosphine and hydrogen sulfide in infrared spectra obtained by Cassini CIRS. As a result we have placed the first upper limits on the stratospheric abundances, which are 1ppb (PH3) and 330ppb (H2S), at the 2-σ significance level. © 2013.
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Uranus' cloud particle properties and latitudinal methane variation from IRTF SpeX observations

Icarus 223:2 (2013) 684-698

Authors:

DS Tice, PGJ Irwin, LN Fletcher, NA Teanby, J Hurley, GS Orton, GR Davis

Abstract:

The Uranian atmosphere was observed in August 2009 from 0.8 to 1.8. μm using the near-infrared spectrometer, SpeX, at NASA's Infrared Telescope Facility. The observations had a spectral resolution of R=. 1200 and an average seeing of between 0.5' in the H-Band (1.4-1.8. μm) and 0.6' in the I-Band (0.8-0.9. μm). The reduced data were analyzed with a multiple-scattering retrieval code. We were able to reproduce observations when using a vertically-compact cloud in the upper troposphere and a vertically-extended, optically-thin haze above the 1-bar level. The existence of these two clouds is consistent with previous studies.The sub-micron portion of the data are most sensitive to very small scattering particles, allowing more insight into particle size than other portions of the infrared spectrum. This portion of the spectrum was therefore of particular interest and was not available in most previous studies of the planet. We assumed the particles in both clouds to be relatively strong forward scatterers (with a Henyey-Greenstein asymmetry factor of g=. 0.7). Given this assumption, we found single-scattering albedos in the tropospheric cloud particles to be ω̄=0.7 at wavelengths above 1.4. μm and to gradually increase to ω̄=1.0 at wavelengths shortward of 1.0. μm. In the upper haze, we found single-scattering albedos to be ω̄=1.0 with the exception of a narrow drop at 1.0. μm to ω̄=0.6. We found a preference for upper haze particle radii at r=. 0.10. μm. Retrievals of base pressure, fractional scale height, and optical depth in both cloud layers showed the best agreement with data when the base pressure of the upper haze was fixed just above the tropospheric clouds, rather than at or above the tropopausal cold trap. We found that these same retrievals strongly preferred tropospheric cloud particles of 1.35-μm radii, and observed cloud top height to increase away from the equator in the case of latitudinally invariant methane abundance.Latitudinal methane variability was also considered, both through a reflectivity study at the 825-nm collision-induced hydrogen absorption feature, as well as through radiative transfer analysis, using forward modeling and retrievals of cloud properties and methane abundance. The data suggested that methane abundance above the tropospheric clouds increased when moving from the midlatitudes towards the equator by at least 9%. The peak of this equatorial methane enrichment was determined to be at 4. ±. 2° S latitude, having moved nearly 15° northward since a reflectance study of 2002 data (Karkoschka and Tomasko, 2009). © 2013 Elsevier Inc.
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On the potential of the EChO mission to characterize gas giant atmospheres

MNRAS 430 (2013) 1188-1207-1188-1207

Authors:

JK Barstow, S Aigrain, PGJ Irwin, N Bowles, LN Fletcher, J-M Lee
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Details from ArXiV

Upper limits for PH3 and H2S in Titan's Atmosphere from Cassini CIRS

(2013)

Authors:

Conor A Nixon, Nicolas A Teanby, Patrick GJ Irwin, Sarah M Horst
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