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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

Seasonal changes in Titan's polar trace gas abundance observed by cassini

Astrophysical Journal Letters 724:1 PART 2 (2010)

Authors:

NA Teanby, PGJ Irwin, R De Kok, CA Nixon

Abstract:

We use a six-year data set (2004-2010) of mid-infrared spectra measured by Cassini's Composite InfraRed Spectrometer to search for seasonal variations in Titan's atmospheric temperature and composition. During most of Cassini's mission Titan's northern hemisphere has been in winter, with an intense stratospheric polar vortex highly enriched in trace gases, and a single south-to-north circulation cell. Following northern spring equinox in mid-2009, dramatic changes in atmospheric temperature and composition were expected, but until now the temporal coverage of polar latitudes has been too sparse to discern trends. Here, we show that during equinox and post-equinox periods, abundances of trace gases at both poles have begun to increase.We propose that increases in north polar trace gases are due to a seasonal reduction in gas depletion by horizontal mixing across the vortex boundary. A simultaneous south polar abundance increase suggests that Titan is now entering, or is about to enter, a transitional circulation regime with two branches, rather than the single branch circulation pattern previously observed. © 2010. The American Astronomical Society. All rights reserved.
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HARMONI: A single-field wide-band integral-field spectrograph for the European ELT

Proceedings of SPIE - The International Society for Optical Engineering 7735:PART 1 (2010)

Authors:

N Thatte, M Tecza, F Clarke, RL Davies, A Remillieux, R Bacon, D Lunney, S Arribas, E Mediavilla, F Gago, N Bezawada, P Ferruit, A Fragoso, D Freeman, J Fuentes, T Fusco, A Gallie, A Garcia, T Goodsall, F Gracia, A Jarno, J Kosmalski, J Lynn, S McLay, D Montgomery, A Pecontal, H Schnetler, H Smith, D Sosa, G Battaglia, N Bowles, L Colina, E Emsellem, A Garcia-Perez, S Gladysz, I Hook, P Irwin, M Jarvis, R Kennicutt, A Levan, A Longmore, J Magorrian, M McCaughrean, L Origlia, R Rebolo, D Rigopoulou, S Ryan, M Swinbank, N Tanvir, E Tolstoy, A Verma

Abstract:

We describe the results of a Phase A study for a single field, wide band, near-infrared integral field spectrograph for the European Extremely Large Telescope (E-ELT). HARMONI, the High Angular Resolution Monolithic Optical & Nearinfrared Integral field spectrograph, provides the E-ELT's core spectroscopic requirement. It is a work-horse instrument, with four different spatial scales, ranging from seeing to diffraction-limited, and spectral resolving powers of 4000, 10000 & 20000 covering the 0.47 to 2.45 μm wavelength range. It is optimally suited to carry out a wide range of observing programs, focusing on detailed, spatially resolved studies of extended objects to unravel their morphology, kinematics and chemical composition, whilst also enabling ultra-sensitive observations of point sources. We present a synopsis of the key science cases motivating the instrument, the top level specifications, a description of the opto-mechanical concept, operation and calibration plan, and image quality and throughput budgets. Issues of expected performance, complementarity and synergies, as well as simulated observations are presented elsewhere in these proceedings[1]. © 2010 Copyright SPIE - The International Society for Optical Engineering.
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Abundances of Jupiter's trace hydrocarbons from Voyager and Cassini

Planetary and Space Science 58:13 (2010) 1667-1680

Authors:

CA Nixon, RK Achterberg, PN Romani, M Allen, X Zhang, NA Teanby, PGJ Irwin, FM Flasar

Abstract:

The flybys of Jupiter by the Voyager spacecraft in 1979, and over two decades later by Cassini in 2000, have provided us with unique datasets from two different epochs, allowing the investigation of seasonal change in the atmosphere. In this paper we model zonal averages of thermal infrared spectra from the two instruments, Voyager 1 IRIS and Cassini CIRS, to retrieve the vertical and meridional profiles of temperature, and the abundances of the two minor hydrocarbons, acetylene (C2H2) and ethane (C 2H6). The spatial variation of these gases is controlled by both chemistry and dynamics, and therefore their observed distribution gives us an insight into both processes. We find that the two gases paint quite different pictures of seasonal change. Whilst the 2-D cross-section of C 2H6 abundance is slightly increased and more symmetric in 2000 (northern summer solstice) compared to 1979 (northern fall equinox), the major trend of equator to pole increase remains. For C2H2 on the other hand, the Voyager epoch exhibits almost no latitudinal variation, whilst the Cassini era shows a marked decrease polewards in both hemispheres. At the present time, these experimental findings are in advance of interpretation, as there are no published models of 2-D Jovian seasonal chemical variation available for comparison. © 2010 Elsevier Ltd. All rights reserved.
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Infrared limb sounding of Titan with the cassini composite infrared spectrometer: Effects of the mid-IR detector spatial responses: Errata

Applied Optics 49:29 (2010) 5575-5576

Authors:

CA Nixon, NA Teanby, SB Calcutt, S Aslam, DE Jennings, VG Kunde, FM Flasar, PGJ Irwin, FW Taylor, DA Glenar, MD Smith

Abstract:

We provide a revised Table 5 for the paper by Nixon et al. [Appl. Opt. 48, 1912 (2009)], in which the abundances of 13CO2 and C 18O were incorrect . © 2010 Optical Society of America.
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Far-infrared opacity sources in Titan's troposphere reconsidered

Icarus 209:2 (2010) 854-857

Authors:

R de Kok, PGJ Irwin, NA Teanby

Abstract:

We use Cassini far-infrared limb and nadir spectra, together with recent Huygens results, to shed new light on the controversial far-infrared opacity sources in Titan's troposphere. Although a global cloud of large CH4 ice particles around an altitude of 30km, together with an increase in tropospheric haze opacity with respect to the stratosphere, can fit nadir and limb spectra well, this cloud does not seem consistent with shortwave measurements of Titan. Instead, the N2-CH4 collision-induced absorption coefficients are probably underestimated by at least 50% for low temperatures. © 2010 Elsevier Inc.
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