Publications by Patrick Irwin

Spectral analysis of Uranus' 2014 bright storm with VLT/SINFONI

Icarus Elsevier 264 (2015) 72-89

P Irwin, LN Fletcher, P Read, D Tice, I de Pater, GS Orton, NA Teanby, GR Davis

An extremely bright storm system observed in Uranus' atmosphere by amateur observers in September 2014 triggered an international campaign to observe this feature with many telescopes across the world. Observations of the storm system in the near infrared were acquired in October and November 2014 with SINFONI on ESO's Very Large Telescope (VLT) in Chile. SINFONI is an Integral Field Unit spectrometer returning 64. ×. 64 pixel images with 2048 wavelengths and uses adaptive optics. Image cubes in the H-band (1.43-1.87. μm) were obtained at spatial resolutions of ~0.1″ per pixel. The observations show that the centre of the storm feature shifts markedly with increasing altitude, moving in the retrograde direction and slightly poleward with increasing altitude. We also see a faint 'tail' of more reflective material to the immediate south of the storm, which again trails in the retrograde direction. The observed spectra were analysed with the radiative transfer and retrieval code, NEMESIS (Irwin et al. [2008]. J. Quant. Spec. Radiat. Transfer, 109, 1136-1150). We find that the storm is well-modelled using either two main cloud layers of a 5-layer aerosol model based on Sromovsky et al. (Sromovsky et al. [2011]. Icarus, 215, 292-312) or by the simpler two-cloud-layer model of Tice et al. (Tice et al. [2013]. Icarus, 223, 684-698). The deep component appears to be due to a brightening (i.e. an increase in reflectivity) and increase in altitude of the main tropospheric cloud deck at 2-3. bars for both models, while the upper component of the feature was modelled as being due to either a thickening of the tropospheric haze of the 2-layer model or a vertical extension of the upper tropospheric cloud of the 5-layer model, assumed to be composed of methane ice and based at the methane condensation level of our assumed vertical temperature and abundance profile at 1.23. bar. We also found this methane ice cloud to be responsible for the faint 'tail' seen to the feature's south and the brighter polar 'hood' seen in all observations polewards of ~45°N for the 5-layer model. During the twelve days between our sets of observations the higher-altitude component of the feature was observed to have brightened significantly and extended to even higher altitudes, while the deeper component faded.

Telling twins apart: Exo-Earths and Venuses with transit spectroscopy

Monthly Notices of the Royal Astronomical Society Oxford University Press 458 (2016) 2657-2666

JK Barstow, S Aigrain, PGJ Irwin, S Kendrew, LN Fletcher

The planned launch of the James Webb Space Telescope (JWST) in 2018 will herald a new era of exoplanet spectroscopy. JWST will be the first telescope sensitive enough to potentially characterize terrestrial planets from their transmission spectra. In this work, we explore the possibility that terrestrial planets with Venus-type and Earth-type atmospheres could be distinguished from each other using spectra obtained by JWST. If we find a terrestrial planet close to the liquid water habitable zone of an M5 star within a distance of 10 parsec, it would be possible to detect atmospheric ozone if present in large enough quantities, which would enable an oxygen-rich atmosphere to be identified. However, the cloudiness of a Venus-type atmosphere would inhibit our ability to draw firm conclusions about the atmospheric composition, making any result ambiguous. Observing small, temperate planets with JWST requires significant investment of resources, with single targets requiring of the order of 100 transits to achieve sufficient signal to noise. The possibility of detecting a crucial feature such as the ozone signature would need to be carefully weighed against the likelihood of clouds obscuring gas absorption in the spectrum.

Exoplanets with JWST: degeneracy, systematics and how to avoid them


JK Barstow, PGJ Irwin, S Kendrew, S Aigrain

Aerosol influence on energy balance of the middle atmosphere of Jupiter.

Nature communications 6 (2015) 10231-

X Zhang, RA West, PGJ Irwin, CA Nixon, YL Yung

Aerosols are ubiquitous in planetary atmospheres in the Solar System. However, radiative forcing on Jupiter has traditionally been attributed to solar heating and infrared cooling of gaseous constituents only, while the significance of aerosol radiative effects has been a long-standing controversy. Here we show, based on observations from the NASA spacecraft Voyager and Cassini, that gases alone cannot maintain the global energy balance in the middle atmosphere of Jupiter. Instead, a thick aerosol layer consisting of fluffy, fractal aggregate particles produced by photochemistry and auroral chemistry dominates the stratospheric radiative heating at middle and high latitudes, exceeding the local gas heating rate by a factor of 5-10. On a global average, aerosol heating is comparable to the gas contribution and aerosol cooling is more important than previously thought. We argue that fractal aggregate particles may also have a significant role in controlling the atmospheric radiative energy balance on other planets, as on Jupiter.

Gas phase dicyanoacetylene (C4N2) on Titan: New experimental and theoretical spectroscopy results applied to Cassini CIRS data

ICARUS 248 (2015) 340-346

A Jolly, V Cottini, A Fayt, L Manceron, F Kwabia-Tchana, Y Benilan, J-C Guillemin, C Nixon, P Irwin

Cometary science. The organic-rich surface of comet 67P/Churyumov-Gerasimenko as seen by VIRTIS/Rosetta.

Science (New York, N.Y.) 347 (2015) aaa0628-

F Capaccioni, A Coradini, G Filacchione, S Erard, G Arnold, P Drossart, MC De Sanctis, D Bockelee-Morvan, MT Capria, F Tosi, C Leyrat, B Schmitt, E Quirico, P Cerroni, V Mennella, A Raponi, M Ciarniello, T McCord, L Moroz, E Palomba, E Ammannito, MA Barucci, G Bellucci, J Benkhoff, JP Bibring, A Blanco, M Blecka, R Carlson, U Carsenty, L Colangeli, M Combes, M Combi, J Crovisier, T Encrenaz, C Federico, U Fink, S Fonti, WH Ip, P Irwin, R Jaumann, E Kuehrt, Y Langevin, G Magni, S Mottola, V Orofino, P Palumbo, G Piccioni, U Schade, F Taylor, D Tiphene, GP Tozzi, P Beck, N Biver, L Bonal, J-P Combe, D Despan, E Flamini, S Fornasier, A Frigeri, D Grassi, M Gudipati, A Longobardo, K Markus, F Merlin, R Orosei, G Rinaldi, K Stephan, M Cartacci, A Cicchetti, S Giuppi, Y Hello, F Henry, S Jacquinod, R Noschese, G Peter, R Politi, JM Reess, A Semery

The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared ranges (5 to 25 and 1.5 to 5% kÅ(-1)), and the broad absorption feature in the 2.9-to-3.6-micrometer range present across the entire illuminated surface are compatible with opaque minerals associated with nonvolatile organic macromolecular materials: a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups. In active areas, the changes in spectral slope and absorption feature width may suggest small amounts of water-ice. However, no ice-rich patches are observed, indicating a generally dehydrated nature for the surface currently illuminated by the Sun.

The EChO science case


G Tinetti, P Drossart, P Eccleston, P Hartogh, K Isaak, M Linder, C Lovis, G Micela, M Ollivier, L Puig, I Ribas, I Snellen, B Swinyard, F Allard, J Barstow, J Cho, A Coustenis, C Cockell, A Correia, L Decin, R de Kok, P Deroo, T Encrenaz, F Forget, A Glasse, C Griffith, T Guillot, T Koskinen, H Lammer, J Leconte, P Maxted, I Mueller-Wodarg, R Nelson, C North, E Palle, I Pagano, G Piccioni, D Pinfield, F Selsis, A Sozzetti, L Stixrude, J Tennyson, D Turrini, M Zapatero-Osorio, J-P Beaulieu, D Grodent, M Guedel, D Luz, HU Norgaard-Nielsen, T Ray, H Rickman, A Selig, M Swain, M Banaszkiewicz, M Barlow, N Bowles, G Branduardi-Raymont, VC du Foresto, J-C Gerard, L Gizon, A Hornstrup, C Jarchow, F Kerschbaum, G Kovacs, P-O Lagage, T Lim, M Lopez-Morales, G Malaguti, E Pace, E Pascale, B Vandenbussche, G Wright, G Ramos Zapata, A Adriani, R Azzollini, A Balado, I Bryson, R Burston, J Colome, M Crook, A Di Giorgio, M Griffin, R Hoogeveen, R Ottensamer, R Irshad, K Middleton, G Morgante, F Pinsard, M Rataj, J-M Reess, G Savini, J-R Schrader, R Stamper, B Winter, L Abe, M Abreu, N Achilleos, P Ade, V Adybekian, L Affer, C Agnor, M Agundez, C Alard, J Alcala, C Allende Prieto, FJ Alonso Floriano, F Altieri, CA Alvarez Iglesias, P Amado, A Andersen, A Aylward, C Baffa, G Bakos, P Ballerini, M Banaszkiewicz, RJ Barber, D Barrado, EJ Barton, V Batista, G Bellucci, JA Belmonte Aviles, D Berry, B Bezard, D Biondi, M Blecka, I Boisse, B Bonfond, P Borde, P Boerner, H Bouy, L Brown, L Buchhave, J Budaj, A Bulgarelli, M Burleigh, A Cabral, MT Capria, A Cassan, C Cavarroc, C Cecchi-Pestellini, R Cerulli, J Chadney, S Chamberlain, S Charnoz, NC Jessen, A Ciaravella, A Claret, R Claudi, A Coates, R Cole, A Collura, D Cordier, E Covino, C Danielski, M Damasso, HJ Deeg, E Delgado-Mena, C Del Vecchio, O Demangeon, A De Sio, J De Wit, M Dobrijevic, P Doel, C Dominic, E Dorfi, S Eales, C Eiroa, M Espinoza Contreras, M Esposito, V Eymet, N Fabrizio, M Fernandez, B Femena Castella, P Figueira, G Filacchione, L Fletcher, M Focardi, S Fossey, P Fouque, J Frith, M Galand, L Gambicorti, P Gaulme, RJ Garcia Lopez, A Garcia-Piquer, W Gear, J-C Gerard, L Gesa, E Giani, F Gianotti, M Gillon, E Giro, M Giuranna, H Gomez, I Gomez-Leal, J Gonzalez Hernandez, B Gonzalez Merino, R Graczyk, D Grassi, J Guardia, P Guio, J Gustin, P Hargrave, J Haigh, E Hebrard, U Heiter, RL Heredero, E Herrero, F Hersant, D Heyrovsky, M Hollis, B Hubert, R Hueso, G Israelian, N Iro, P Irwin, S Jacquemoud, G Jones, H Jones, K Justtanont, T Kehoe, F Kerschbaum, E Kerins, P Kervella, D Kipping, T Koskinen, N Krupp, O Lahav, B Laken, N Lanza, E Lellouch, G Leto, J Licandro Goldaracena, C Lithgow-Bertelloni, SJ Liu, U Lo Cicero, N Lodieu, P Lognonne, M Lopez-Puertas, MA Lopez-Valverde, IL Rasmussen, A Luntzer, P Machado, C MacTavish, A Maggio, J-P Maillard, W Magnes, J Maldonado, U Mall, J-B Marquette, P Mauskopf, F Massi, A-S Maurin, A Medvedev, C Michaut, P Miles-Paez, M Montalto, P Montanes Rodriguez, M Monteiro, D Montes, H Morais, JC Morales, M Morales-Calderon, G Morello, A Moro Martin, J Moses, A Moya Bedon, F Murgas Alcaino, E Oliva, G Orton, F Palla, M Pancrazzi, E Pantin, V Parmentier, H Parviainen, KY Pena Ramirez, J Peralta, S Perez-Hoyos, R Petrov, S Pezzuto, R Pietrzak, E Pilat-Lohinger, N Piskunov, R Prinja, L Prisinzano, I Polichtchouk, E Poretti, A Radioti, AA Ramos, T Rank-Lueftinger, P Read, K Readorn, R Rebolo Lopez, J Rebordao, M Rengel, L Rezac, M Rocchetto, F Rodler, VJ Sanchez Bejar, AS Lavega, E Sanroma, N Santos, J Sanz Forcada, G Scandariato, F-X Schmider, A Scholz, S Scuderi, J Sethenadh, S Shore, A Showman, B Sicardy, P Sitek, A Smith, L Soret, S Sousa, A Stiepen, M Stolarski, G Strazzulla, HM Tabernero, P Tanga, M Tecsa, J Temple, L Terenzi, M Tessenyi, L Testi, S Thompson, H Thrastarson, BW Tingley, M Trifoglio, J Martin Torres, A Tozzi, D Turrini, R Varley, F Vakili, M de Val-Borro, ML Valdivieso, O Venot, E Villaver, S Vinatier, S Viti, I Waldmann, D Waltham, D Ward-Thompson, R Waters, C Watkins, D Watson, P Wawer, A Wawrzaszek, G White, T Widemann, W Winek, T Wisniowski, R Yelle, Y Yung, SN Yurchenko

Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching


JK Barstow, S Aigrain, PGJ Irwin, S Kendrew, LN Fletcher

Evolution of Stratospheric Chemistry in the Saturn Storm Beacon Region.

Icarus 261 (2015) 149-168

JI Moses, ES Armstrong, LN Fletcher, AJ Friedson, PGJ Irwin, JA Sinclair, BE Hesman

The giant northern-hemisphere storm that erupted on Saturn in December 2010 triggered significant changes in stratospheric temperatures and species abundances that persisted for more than a year after the original outburst. The stratospheric regions affected by the storm have been nicknamed "beacons" due to their prominent infrared-emission signatures (Fletcher, L.N. et al. [2011]. Science 332, 1413). The two beacon regions that were present initially merged in April 2011 to form a single, large, anticyclonic vortex (Fletcher, L.N. et al. [2012]. Icarus 221, 560). We model the expected photochemical evolution of the stratospheric constituents in the beacons from the initial storm onset through the merger and on out to March 2012. The results are compared with longitudinally resolved Cassini/CIRS spectra from May 2011. If we ignore potential changes due to vertical winds within the beacon, we find that C2H2, C2H6, and C3H8 remain unaffected by the increased stratospheric temperatures in the beacon, the abundance of the shorter-lived CH3C2H decreases, and the abundance of C2H4 increases significantly due to the elevated temperatures, the latter most notably in a secondary mixing-ratio peak located near mbar pressures. The C4H2 abundance in the model decreases by a factor of a few in the 0.01-10 mbar region but has a significant increase in the 10-30 mbar region due to evaporation of the previously condensed phase. The column abundances of C6H6 and H2O above ~30 mbar also increase due to aerosol evaporation. Model-data comparisons show that models that consider temperature changes alone underpredict the abundance of C2H x species by a factor of 2-7 in the beacon core in May 2011, suggesting that other processes not considered by the models, such as downwelling winds in the vortex, are affecting the species profiles. Additional calculations indicate that downwelling winds of order -10 cm s -1 near ~0.1 mbar need to be included in the photochemical models in order to explain the inferred C2H x abundances in the beacon core, indicating that both strong subsiding winds and chemistry at elevated temperatures are affecting the vertical profiles of atmospheric constituents in the beacon. We (i) discuss the general chemical behavior of stratospheric species in the beacon region, (ii) demonstrate how the evolving beacon environment affects the species vertical profiles and emission characteristics (both with and without the presence of vertical winds), (iii) make predictions with respect to compositional changes that can be tested against Cassini and Herschel data, and higher-spectral-resolution ground-based observations of the beacon region, and (iv) discuss future measurements and modeling that could further our understanding of the dynamical origin, evolution, and chemical processing within these unexpected stratospheric vortices that were generated after the 2010 convective event.

On the detectability of trace chemical species in the martian atmosphere using gas correlation filter radiometry

ICARUS 260 (2015) 103-127

JA Sinclair, PGJ Irwin, SB Calcutt, EL Wilson

Cloud structure and composition of Jupiter's troposphere from 5-mu m Cassini VIMS spectroscopy

ICARUS 257 (2015) 457-470

RS Giles, LN Fletcher, PGJ Irwin

Titan's Complex Atmospheric Chemistry Revealed by ALMA


MA Cordiner, CA Nixon, MY Palmer, SB Charnley, J Serigano, MJ Mumma, SN Milam, NA Teanby, PGJ Irwin, Z Kisiel, AJ Remijan, Y-J Kuan, Y-L Chuang, DC Lis

Transit spectroscopy with JWST: systematics, star-spots and stitching (vol 448, pg 2546, 2015)


JK Barstow, S Aigrain, PGJ Irwin, S Kendrew, LN Fletcher

Reanalysis of Uranus' cloud scattering properties from IRTF/SpeX observations using a self-consistent scattering cloud retrieval scheme

ICARUS 250 (2015) 462-476

PGJ Irwin, DS Tice, LN Fletcher, JK Barstow, NA Teanby, GS Orton, GR Davis

Seasonal evolution of Saturn's polar temperatures and composition

ICARUS 250 (2015) 131-153

LN Fletcher, PGJ Irwin, JA Sinclair, GS Orton, RS Giles, J Hurley, N Gorius, RK Achterberg, BE Hesman, GL Bjoraker

The Long wave (11-16 mu m) spectrograph for the EChO M3 Mission Candidate study


NE Bowles, M Tecza, JK Barstow, JM Temple, PGJ Irwin, LN Fletcher, S Calcutt, J Hurley, M Ferlet, D Freeman



MA Cordiner, MY Palmer, CA Nixon, PGJ Irwin, NA Teanby, SB Charnley, MJ Mumma, Z Kisiel, J Serigano, Y-J Kuan, Y-L Chuang, K-S Wang

Exoplanet atmospheres with EChO: spectral retrievals using EChOSim


JK Barstow, NE Bowles, S Aigrain, LN Fletcher, PGJ Irwin, R Varley, E Pascale

The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets


CS Arridge, N Achilleos, J Agarwal, CB Agnor, R Ambrosi, N Andre, SV Badman, K Baines, D Banfield, M Barthelemy, MM Bisi, J Blum, T Bocanegra-Bahamon, B Bonfond, C Bracken, P Brandt, C Briand, C Briois, S Brooks, J Castillo-Rogez, T Cavalie, B Christophe, AJ Coates, G Collinson, JF Cooper, M Costa-Sitja, R Courtin, IA Daglis, I De Pater, M Desai, D Dirkx, MK Dougherty, RW Ebert, G Filacchione, LN Fletcher, J Fortney, I Gerth, D Grassi, D Grodent, E Grun, J Gustin, M Hedman, R Helled, P Henri, S Hess, JK Hillier, MH Hofstadter, R Holme, M Horanyi, G Hospodarsky, S Hsu, P Irwin, CM Jackman, O Karatekin, S Kempf, E Khalisi, K Konstantinidis, H Kruger, WS Kurth, C Labrianidis, V Lainey, LL Lamy, M Laneuville, D Lucchesi, A Luntzer, J MacArthur, A Maier, A Masters, S McKenna-Lawlor, H Melin, A Milillo, G Moragas-Klostermeyer, A Morschhauser, JI Moses, O Mousis, N Nettelmann, FM Neubauer, T Nordheim, B Noyelles, GS Orton, M Owens, R Peron, C Plainaki, F Postberg, N Rambaux, K Retherford, S Reynaud, E Roussos, CT Russell, A Rymer, R Sallantin, A Sanchez-Lavega, O Santolik, J Saur, K Sayanagi, P Schenk, J Schubert, N Sergis, EC Sittler, A Smith, F Spahn, R Srama, T Stallard, V Sterken, Z Sternovsky, M Tiscareno, G Tobie, F Tosi, M Trieloff, D Turrini, EP Turtle, S Vinatier, R Wilson, P Zarkat

Scientific rationale for Saturn's in situ exploration


O Mousis, LN Fletcher, JP Lebreton, P Wurz, T Cavalie, A Coustenis, R Courtin, D Gautier, R Helled, PGJ Irwin, AD Morse, N Nettelmann, B Marty, P Rousselot, O Venot, DH Atkinson, JH Waite, KR Reh, AA Simon, S Atreya, N Andre, M Blanc, IA Daglis, G Fischer, WD Geppertt, T Guillot, MM Hedman, R Hueso, E Lellouch, JI Lunine, CD Murray, J O'Donoghue, M Rengel, A Sanchez-Lavega, FX Schmider, A Spiga, T Spilker, J-M Petit, MS Tiscareno, M Ali-Dib, K Altwegg, SJ Bolton, A Bouquet, C Briois, T Fouchet, S Guerlet, T Kostiuk, D Lebleu, R Moreno, GS Orton, J Poncy