Publications by Colin Wilson


The thermal structure of the Venus atmosphere: Intercomparison of Venus Express and ground based observations of vertical temperature and density profiles

ICARUS 294 (2017) 124-155

SS Limaye, S Lebonnois, A Mahieux, M Paetzold, S Bougher, S Bruinsma, S Chamberlain, RT Clancy, J-C Gerard, G Gilli, D Grassi, R Haus, M Herrmann, T Imamura, E Kohler, P Krause, A Migliorini, F Montmessin, C Pere, M Persson, A Piccialli, M Rengel, A Rodin, B Sandor, M Sornig, H Svedhem, S Tellmann, P Tanga, AC Vandaele, T Widemann, CF Wilson, I Mueller-Wodarg, L Zasova


Sulfur dioxide in the Venus atmosphere: I. Vertical distribution and variability

ICARUS 295 (2017) 16-33

AC Vandaele, O Korablev, D Belyaev, S Chamberlain, D Evdokimova, T Encrenaz, L Esposito, KL Jessup, F Lefevre, S Limaye, A Mahieux, E Marcq, FP Mills, F Montmessin, CD Parkinson, S Robert, T Roman, B Sandor, A Stolzenbach, C Wilson, V Wilquet


Sulfur dioxide in the Venus Atmosphere: II. Spatial and temporal variability

ICARUS 295 (2017) 1-15

AC Vandaele, O Korablev, D Belyaev, S Chamberlain, D Evdokimova, T Encrenaz, L Esposito, KL Jessup, F Lefevre, S Limaye, A Mahieux, E Marcq, FP Mills, F Montmessin, CD Parkinson, S Robert, T Roman, B Sandor, A Stolzenbach, C Wilson, V Wilquet


The ExoMars DREAMS scientific data archive

SOFTWARE AND CYBERINFRASTRUCTURE FOR ASTRONOMY IV 9913 (2016)

P Schipani, L Marty, M Mannetta, F Esposito, C Molfese, A Aboudan, V Apestigue-Palacio, I Arruego-Rodriguez, C Bettanini, G Colombatti, S Debei, M Genzer, A-M Harri, E Marchetti, F Montmessin, R Mugnuolo, S Pirrotta, C Wilson


Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

Planetary and Space Science 113-114 (2015) 33-48

MW Airey, TA Mather, DM Pyle, LS Glaze, RC Ghail, CF Wilson

© 2015 The Authors. Abstract We investigate the conditions that will promote explosive volcanic activity on Venus. Conduit processes were simulated using a steady-state, isothermal, homogeneous flow model in tandem with a degassing model. The response of exit pressure, exit velocity, and degree of volatile exsolution was explored over a range of volatile concentrations (H < inf > 2 < /inf > O and CO < inf > 2 < /inf > ), magma temperatures, vent altitudes, and conduit geometries relevant to the Venusian environment. We find that the addition of CO < inf > 2 < /inf > to an H < inf > 2 < /inf > O-driven eruption increases the final pressure, velocity, and volume fraction gas. Increasing vent elevation leads to a greater degree of magma fragmentation, due to the decrease in the final pressure at the vent, resulting in a greater likelihood of explosive activity. Increasing the magmatic temperature generates higher final pressures, greater velocities, and lower final volume fraction gas values with a correspondingly lower chance of explosive volcanism. Cross-sectionally smaller, and/or deeper, conduits were more conducive to explosive activity. Model runs show that for an explosive eruption to occur at Scathach Fluctus, at Venus' mean planetary radius (MPR), 4.5% H < inf > 2 < /inf > O or 3% H < inf > 2 < /inf > O with 3% CO < inf > 2 < /inf > (from a 25 m radius conduit) would be required to initiate fragmentation; at Ma'at Mons (~9 km above MPR) only ~2% H < inf > 2 < /inf > O is required. A buoyant plume model was used to investigate plume behaviour. It was found that it was not possible to achieve a buoyant column from a 25 m radius conduit at Scathach Fluctus, but a buoyant column reaching up to ~20 km above the vent could be generated at Ma'at Mons with an H < inf > 2 < /inf > O concentration of 4.7% (at 1300 K) or a mixed volatile concentration of 3% H < inf > 2 < /inf > O with 3% CO < inf > 2 < /inf > (at 1200 K). We also estimate the flux of volcanic gases to the lower atmosphere of Venus, should explosive volcanism occur. Model results suggest explosive activity at Scathach Fluctus would result in an H < inf > 2 < /inf > O flux of ~10 < sup > 7 < /sup > kg s < sup > -1 < /sup > . Were Scathach Fluctus emplaced in a single event, our model suggests that it may have been emplaced in a period of ~15 days, supplying 1-2×10 < sup > 4 < /sup > Mt H < inf > 2 < /inf > O to the atmosphere locally. An eruption of this scale might increase local atmospheric H < inf > 2 < /inf > O abundance by several ppm over an area large enough to be detectable by near-infrared nightside sounding using the 1.18 μm spectral window such as that carried out by the Venus Express/VIRTIS spectrometer. Further interrogation of the VIRTIS dataset is recommended to search for ongoing volcanism on Venus.


The CO<inf>2</inf> continuum absorption in the 1.10- and 1.18-μm windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express

Planetary and Space Science 113-114 (2015) 66-77

A Fedorova, B Bézard, JL Bertaux, O Korablev, C Wilson

© 2014 Elsevier Ltd. Abstract One of the difficulties in modeling Venus' nightside atmospheric windows is the need to apply CO 2 continuum opacity due to collision-induced CO 2 bands and/or extreme far wings of strong allowed CO 2 bands. Characterizing the CO 2 continuum absorption at near-IR wavelengths as well as searching for a possible vertical gradient of minor species near the surface require observations over different surface elevations. The largest change in altitude occurs during a passage above Maxwell Montes at high northern latitudes. In 2011, 2012 and 2013 the SPICAV instrument aboard the Venus Express satellite performed three sets of observations over Maxwell Montes with variation of surface altitude from -2 to 9 km in the 1.10, 1.18 and 1.28-μm windows. The retrieved CO 2 continuum absorption for the 1.10- and 1.18-μm windows varies from 0.29 to 0.66×10 -9 cm -1 amagat -2 and from 0.30 to 0.78×10 -9 cm -1 amagat -2 , respectively, depending on the assumed input parameters. The retrieval is sensitive to possible variations of the surface emissivity. Our values fall between the results of Bézard et al., (2009, 2011) based on VIRTIS-M observations and laboratory measurements by Snels et al. (2014). We can also conclude that the continuum absorption at 1.28 μm can be constrained below 2.0×10 -9 cm -1 amagat -2 . Based on the 1.18 μm window the constant H 2 O mixing ratio varying from 25.7 +1.4 -1.2 ppm to 29.4 +1.6 -1.4 ppm has been retrieved assuming the surface emissivity of 0.95 and 0.6, respectively. No firm conclusion from SPICAV data about the vertical gradient of water vapor content at 10-20 km altitude could be drawn because of low signal-to-noise ratio and uncertainties in the surface emissivity.


Coordinated Hubble Space Telescope and Venus Express Observations of Venus' upper cloud deck

ICARUS 258 (2015) 309-336

KL Jessup, E Marcq, F Mills, A Mahieux, S Limaye, C Wilson, M Allen, J-L Bertaux, W Markiewicz, T Roman, A-C Vandaele, V Wilquet, Y Yung


Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

PLANETARY AND SPACE SCIENCE 113 (2015) 33-48

MW Airey, TA Mather, DM Pyle, LS Glaze, RC Ghail, CF Wilson


A new, fast and flexible radiative transfer method for Venus general circulation models

PLANETARY AND SPACE SCIENCE 105 (2015) 80-93

JM Mendonca, PL Read, CF Wilson, C Lee


The CO2 continuum absorption in the 1.10-and 1.18-mu m windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express

PLANETARY AND SPACE SCIENCE 113 (2015) 66-77

A Fedorova, B Bezard, J-L Bertaux, O Korablev, C Wilson


The CO2 continuum absorption in the 1.10- and 1.18-μm windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express

Planetary and Space Science (2014)

A Fedorova, A Fedorova, B Bézard, JL Bertaux, O Korablev, O Korablev, C Wilson

© 2014 Elsevier Ltd. One of the difficulties in modeling Venus' nightside atmospheric windows is the need to apply CO2 continuum opacity due to collision-induced CO2 bands and/or extreme far wings of strong allowed CO2 bands. Characterizing the CO2 continuum absorption at near-IR wavelengths as well as searching for a possible vertical gradient of minor species near the surface require observations over different surface elevations. The largest change in altitude occurs during a passage above Maxwell Montes at high northern latitudes. In 2011, 2012 and 2013 the SPICAV instrument aboard the Venus Express satellite performed three sets of observations over Maxwell Montes with variation of surface altitude from -2 to 9km in the 1.10, 1.18 and 1.28-μm windows. The retrieved CO2 continuum absorption for the 1.10- and 1.18-μm windows varies from 0.29 to 0.66×10-9 cm-1 amagat-2 and from 0.30 to 0.78×10-9 cm-1 amagat-2, respectively, depending on the assumed input parameters. The retrieval is sensitive to possible variations of the surface emissivity. Our values fall between the results of Bézard et al., (2009, 2011) based on VIRTIS-M observations and laboratory measurements by Snels et al. (2014). We can also conclude that the continuum absorption at 1.28μm can be constrained below 2.0×10-9 cm-1 amagat-2. Based on the 1.18μm window the constant H2O mixing ratio varying from 25.7+1.4 -1.2 ppm to 29.4+1.6 -1.4 ppm has been retrieved assuming the surface emissivity of 0.95 and 0.6, respectively. No firm conclusion from SPICAV data about the vertical gradient of water vapor content at 10-20km altitude could be drawn because of low signal-to-noise ratio and uncertainties in the surface emissivity.


Venus express: Lessons from 8 years of science operations

13th International Conference on Space Operations, SpaceOps 2014 (2014)

DR Merritt, RMT Hoofs, MP Ayúcar, CF Wilson

The Venus Express spacecraft was launched in November 2005. This first European mission to Venus arrived at the planet in April 2006, and within a month had completed on-orbit commissioning and was returning science data to Earth. After four mission extensions and eight years, the spacecraft continues to operate successfully. The end of the mission is anticipated to be in 2014, when the on-board fuel supplies are finally exhausted and the required orbit around Venus can no longer be maintained. This paper discusses the lessons learned by the Venus Express Science Operations Centre (VSOC) over the course of the eight year mission, and briefly discusses the plans for the end of the mission.


The DREAMS experiment on the ExoMars 2016 mission for the study of Martian environment during the dust storm season

2014 IEEE INTERNATIONAL WORKSHOP ON METROLOGY FOR AEROSPACE (METROAEROSPACE) (2014) 167-173

C Bettanini, F Esposito, S Debei, C Molfese, I Arruego Rodriguez, G Colombatti, A-M Harri, F Montmessin, C Wilson, A Aboudan, S Abbaki, V Apestigue, G Bellucci, J-J Berthelier, JR Brucato, SB Calcutt, F Cortecchia, G Di Achille, F Ferri, F Forget, GP Guizzo, E Friso, M Genzer, P Gilbert, H Haukka, JJ Jimenez, S Jimenez, J-L Josset, O Karatekin, G Landis, R Lorenz, J Martinez, MV Mennella, D Moehlmann, D Moirin, R Molinaro, E Palomba, M Patell, J-P Pommereau, CI Popa, S Rafkin, P Rannou, NO Renno, P Schipani, W Schmidt, S Silvestro, F Simoes, A Spiga, F Valero, L Vazquez, F Vivat, O Witasse, R Mugnuolo, S Pirrotta, E Marchetti, IEEE


Characterizing atmospheric waves on Venus, Earth, and Mars

Eos 93 (2012) 220-

CF Wilson, A Piccialli

Atmospheric Waves Workshop; Noordwijk, Netherlands, 9-10 November 2011 Experts in observations and modeling of atmospheric waves from the Earth and planetary atmospheric science communities came together at a November 2011 workshop held at the European Space Agency's (ESA) European Space Research and Technology Centre (ESTEC) site in the Netherlands to discuss the nature of waves observed in Venus's atmosphere and their comparison to those on Earth and Mars. ESA's Venus Express (VEx) satellite and ground-based observers find atmospheric waves at many scales. Migrating solar tides and other planetary-scale waves are observed in cloud-tracking wind vectors and temperature fields. Mesoscale gravity waves (GWs) can also be seen at a variety of levels from the cloud base up to the thermosphere, evident in imagery and in vertical profiles of temperature, density, and aerosol abundance. This workshop focused particularly on GWs, as their role in the atmospheric circulation is still poorly understood. © 2012 American Geophysical Union. All Rights Reserved.


The 2010 European Venus Explorer (EVE) mission proposal

Experimental Astronomy 33 (2012) 305-335

CF Wilson, E Chassefière, E Hinglais, KH Baines, TS Balint, JJ Berthelier, J Blamont, G Durry, CS Ferencz, RE Grimm, T Imamura, JL Josset, F Leblanc, S Lebonnois, JJ Leitner, SS Limaye, B Marty, E Palomba, SV Pogrebenko, SCR Rafkin, DL Talboys, R Wieler, LV Zasova, C Szopa

The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an 'M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (~25°C and ~0. 5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond. © 2011 Springer Science+Business Media B.V.


Models of the global cloud structure on Venus derived from Venus Express observations

Icarus 217 (2012) 542-560

JK Barstow, CCC Tsang, CF Wilson, PGJ Irwin, FW Taylor, K McGouldrick, P Drossart, G Piccioni, S Tellmann

Spatially-resolved near-infrared spectra from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express have been used to derive improved models of the vertical structure and global distribution of cloud properties in the southern hemisphere of Venus. VIRTIS achieved the first systematic, global mapping of Venus at wavelengths within transparency windows in the 1.6-2.6. μm range, which are sensitive on the nightside to absorption by the lower and middle cloud layers of thermally-emitted radiation from the hot lower atmosphere (Taylor, F.W., Crisp, D., Bézard, B. [1997]. Venus II: Geology, Geophysics, Atmosphere, and Solar Wind Environment, pp. 325-351). The cloud model used to interpret the spectra is based on previous work by Pollack et al. (Pollack, J., Dalton, J., Grinspoon, D., Wattson, R., Freedman, R., Crisp, D., Allen, D., Bézard, B., de Bergh, C., Giver, L. [1993] . Icarus 103, 1-42), Grinspoon et al. (Grinspoon, D.H., Pollack, J.B., Sitton, B.R., Carlson, R.W., Kamp, L.W., Baines, K.H., Encrenaz, T., Taylor, F.W. [1993]. Planet. Space Sci. 41, 515-542) and Crisp (Crisp, D. [1986] . Icarus 67, 484-514), and assumes a composition for the cloud particles of sulfuric acid and water, with acid concentration as a free parameter to be determined. Other retrieved parameters are the average size of the particles and the altitude of the cloud base in the model. Latitudinal variation in the atmospheric temperature structure was incorporated using data from the Venus Radio Science experiment (VeRa). Values are estimated initially using wavelength pairs selected for their unique sensitivity to each parameter, and then validated by comparing measured to calculated spectra over the entire wavelength range, the latter generated using the NEMESIS radiative transfer and retrieval code (Irwin, P.G.J., Teanby, N.A., de Kok, R., Fletcher, L.N., Howett, C.J.A., Tsang, C.C.C., Wilson, C.F., Calcutt, S.B., Nixon, C.A., Parrish, P.D. [2008]. J. Quant. Spectrosc. Radiat. Trans. 109, 1136-1150). The sulfuric acid concentration in the cloud particles is found to be higher in regions of optically thick cloud. The cloud base altitude shows a dependence on latitude, reaching a maximum height near -50°. The increased average particle size near the pole found by Wilson et al. (Wilson, C.F., Guerlet, S., Irwin, P.G.J., Tsang, C.C.C., Taylor, F.W., Carlson, R.W., Drossart, P., Piccioni, G. [2008] . J. Geophys. Res. (Planets) 113, E12) and the finding of spatially variable water vapor abundance at35-40. km altitude first reported by Tsang et al. (Tsang, C.C.C., Wilson, C.F., Barstow, J.K., Irwin, P.G.J., Taylor, F.W., McGouldrick, K., Piccioni, G., Drossart, P., Svedhem, H. [2010]. Geophys. Res. Lett. 37, L02202) are both confirmed. The implications of these improved descriptions of cloud structure and variability for the chemistry, meteorology, and radiative energy balance on Venus are briefly discussed. © 2011 Elsevier Inc.


Zonal winds at high latitudes on Venus: An improved application of cyclostrophic balance to Venus Express observations

Icarus 217 (2012) 629-639

JM Mendonça, PL Read, CF Wilson, SR Lewis

Recent retrievals of zonal thermal winds obtained in a cyclostrophic regime on Venus are generally consistent with cloud tracking measurements at mid-latitudes, but become unphysical in polar regions where the values obtained above the clouds are often less than or close to zero. Using a global atmospheric model, we show that the main source of errors that appear in the polar regions when retrieving the zonal thermal winds is most likely due to uncertainties in the zonal wind intensity in the choice of the lower boundary condition.Here we suggest a new and robust method to better estimate the lower boundary condition for high latitudes, thereby improving the retrieved zonal thermal winds throughout the high latitudes middle atmosphere. This new method is applied to temperature fields derived from Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) data on board the Venus Express spacecraft. We obtain a zonal thermal wind field that is in better agreement with other, more direct methods based on either retrieving the zonal winds from cloud tracking or from direct measurements of the meridional slope of pressure surfaces. © 2011 Elsevier Inc.


EnVision: Taking the pulse of our twin planet

Experimental Astronomy 33 (2012) 337-363

RC Ghail, C Wilson, M Galand, D Hall, C Cochrane, P Mason, J Helbert, F MontMessin, S Limaye, M Patel, N Bowles, D Stam, JE Wahlund, F Rocca, D Waltham, TA Mather, J Biggs, M Genge, P Paillou, K Mitchell, L Wilson, UN Singh

EnVision is an ambitious but low-risk response to ESA's call for a medium-size mission opportunity for a launch in 2022. Venus is the planet most similar to Earth in mass, bulk properties and orbital distance, but has evolved to become extremely hostile to life. EnVision's 5-year mission objectives are to determine the nature of and rate of change caused by geological and atmospheric processes, to distinguish between competing theories about its evolution and to help predict the habitability of extrasolar planets. Three instrument suites will address specific surface, atmosphere and ionosphere science goals. The Surface Science Suite consists of a 2.2 m 2 radar antenna with Interferometer, Radiometer and Altimeter operating modes, supported by a complementary IR surface emissivity mapper and an advanced accelerometer for orbit control and gravity mapping. This suite will determine topographic changes caused by volcanic, tectonic and atmospheric processes at rates as low as 1 mm a -1 . The Atmosphere Science Suite consists of a Doppler LIDAR for cloud top altitude, wind speed and mesospheric structure mapping, complemented by IR and UV spectrometers and a spectrophotopolarimeter, all designed to map the dynamic features and compositions of the clouds and middle atmosphere to identify the effects of volcanic and solar processes. The Ionosphere Science Suite uses a double Langmiur probe and vector magnetometer to understand the behaviour and long-term evolution of the ionosphere and induced magnetosphere. The suite also includes an interplanetary particle analyser to determine the delivery rate of water and other components to the atmosphere. © 2011 Springer Science+Business Media B.V.


Venus's southern polar vortex reveals precessing circulation

Science 332 (2011) 577-580

D Luz, DL Berry, G Piccioni, P Drossart, R Politi, CF Wilson, S Erard, F Nuccilli

Initial images of Venus's south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet's north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ∼3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.


A balloon-borne mission to observe Venus during the January 2014 inferior conjunction

European Space Agency, (Special Publication) ESA SP 700 SP (2011) 379-386

E Young, M Bullock, C Tsang, J Fox, R Mellon, T Widemann, C Wilson

We describe a stratospheric balloon mission that will make continuous observations of Venus over a period of several weeks during the January 2014 inferior conjunction. NASA's balloon program has historically supported Antarctic flights like this one in the eliophysics and Astrophysics Divisions. The proposed experiment consists of a one meter telescope, two imaging detectors operating from 0.35 to 2.55 ! m at the diffraction limit and 33 filters. This mission will address a number of questions regarding (a) Venus' super-rotation and general circulation, (b) the properties of Venus' clouds, (c) the distribution of trace species and the coupling between certain dynamical and chemical processes, (d) the existence and prevalence of lightning on Venus, and (e) the distribution of thermal emissivity anomalies on Venus' surface. We call this mission VSS (Venus StratoScope) to keep in mind the legacy of the Stratoscope and Stratoscope II balloon missions.

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