Planetary atmosphere observation analysis: publications

Preliminary atmospheric study of Jupiter using ISO/SWS data

(2022)

Authors:

José Ribeiro, Pedro Machado, Santiago Pérez-Hoyos, João Dias, Patrick Irwin

Abstract:

The study of the thermal spectrum of Jupiter gives us the possibility to study the elements that constitute the Jovian atmosphere, allowing us to infer the formation history and conditions of the giant planet (Taylor et al., 2004). Determining the abundance of chemical species and isotopic ratios is fundamental in this regard. For this, we reanalyse 1997 Jupiter data obtained by the ESA mission Infrared Space Observatory (ISO) (Kessler et al., 1996) in the 793.65-3125 cm-1 (3.2-12.6 &#181;m) region using the Short-Wave Spectrometer (SWS) (de Graauw et al., 1996). &#160;Despite the age of this data, we argue that it warrants a revisit and reanalysis since it was an important step in the study of Jupiter&#8217;s atmosphere and there have since been advancements in atmospheric models and line data.In this work we used the NEMESIS radiative transfer suite (Irwin et al. 2008) to reproduce the observations from Encrenaz et al. (1999), which will also work as a validation of our method. Using the Cassini/CIRS model as a starting point, we adapted the template for the ISO/SWS data. We compiled correlated k-tables from the spectral line database from Fletcher et al. (2018) for a NH3, PH3, 12CH3D, 12CH4, 13CH4, C2H2, C2H6, C2H4, C4H2, He and H2 atmosphere.<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.ece30d39628269873172561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=967973decff35ea7a1891e34420767cf&ct=x&pn=gnp.elif&d=1" alt="" width="792" height="462">Figure 1: Plot of ISO/SWS and CIRS observations showing the discrepancy between both (no offset applied)We first compare the spectrum obtained by ISO/SWS with the a priori model in order to find discrepancies between them as well as how each molecule individually impacts the forward model (Figure 1).Our current work is focused on the 793.65-1500 cm-1 (6.7-12.6 &#181;m) region of the spectrum, for comparison reasons between the CIRS and ISO-SWS data, with the 793.65-1200 cm-1 (8.3-12.6 &#181;m) region showing the best fit.We present here our preliminary results of the study of abundances of 12CH3D, 12CH4, 13CH4, C2H2 and C2H6 of Jupiter&#8217;s atmosphere as well as our study of the pressure-temperature profile of Jupiter obtained using NEMESIS retrievals. We also compare our results with the profiles and abundances from Neimann et al. (1998) and Fletcher et al. (2016) with the aim of constraining the number of possible best fit profiles.As consequence of the former study, we also present our initial study of the H/D and 12C/13C isotopic ratio of the Jovian atmosphere from the abundances of 12CH3D, 13CH4 and 12CH4 following the methodology from Fouchet et al. (2000).We hope with this work to advance the understanding of the atmosphere of Jupiter and the physical and chemical processes that occur, as well as better determining its vertical distribution of chemical species and thermal profile. As future work, we expect to extend our frequency domain to the full range of ISO/SWS observations, study the 15N/14N ratio and compare our finding with other relevant results.&#160;&#160;References:<ul><li>de Graauw et al., Observing with the ISO short-wavelength spectrometer, A&A 315, L49-L54, 1996</li> <li>Encrenaz et al., The atmospheric composition and structure of Jupiter and Saturn form ISO observations: a preliminary review, Planetary and Space Science 47, 1225-1242, 1999</li> <li>Fletcher et al., Mid-infrared mapping of Jupiter&#8217;s temperatures, aerosol opacity and chemical distributions with IRTF/TEXES, Icarus 278, 128&#8211;161, 2016</li> <li>Fletcher et al., A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex, Nature Communications, Volume 9, 2018.</li> <li>Fouchet et al., ISO-SWS Observations of Jupiter: Measurement of the Ammonia Tropospheric Profile and of the 15N/14N Isotopic Ratio, Icarus 143, 223&#8211;243, 2000</li> <li>Irwin et al., The NEMESIS planetary atmosphere radiative transfer and retrieval tool, Journal of Quantitative Spectroscopy & Radiative Transfer 109, 1136&#8211;1150, 2008</li> <li>Kessler et al., The Infrared Space Observatory (ISO) mission, A&A 315, L27, 1996</li> <li>Neimann et al., The composition of the Jovian atmosphere as determined by the Galileo probe mass spectrometer, Journal of Geophysical Research Atmospheres 103(E10):22831-45, 1998</li> <li>Taylor et al., Jupiter, The Planet, Satellites and Magnetosphere, Ch.4, Cambridge Planetary Science, Eds. Bagenal, Dowling, McKinnon, 2004</li> </ul>&#160;Acknowledgements:We thank Th&#233;r&#232;se Encrenaz, from LESIA, Observatoire de Paris, for providing the data for this work, Patrick Irwin, from the University of Oxford (UK), for the help with the NEMESIS radiative transfer suite and Maarten Roos-Serote for guidance and help in analysing the data and retrieval results.We acknowledge support from the Portuguese Funda&#231;&#227;o Para a Ci&#234;ncia e a Tecnologia (ref. PTDC/FIS-AST/29942/2017) through national funds and by FEDER through COMPETE 2020 (ref. POCI-01-0145 FEDER-007672) and through a grant of reference 2021.04584.BD.&#160;

More details from the publisher

Stratospheric HCN and Evolution of a Mixing Barrier in Titan’s Equatorial Region from Low-Resolution Cassini/CIRS Spectra

(2022)

Authors:

Lucy Wright, Nicholas A Teanby, Patrick GJ Irwin, Conor A Nixon, Dann M Mitchell

Abstract:

1.&#160; Introduction Titan is the only moon in our solar system with a substantial atmosphere. It comprises 98% Nitrogen (Niemann et al., 2005), and is rich in hydrocarbon (CxHy) and nitrile (CxHyNz) species. Such species photochemically react to produce organic aerosols which compose a thick orange haze suspended in Titan&#8217;s middle atmosphere. Global Circulation Models (GCMs) predict the meridional circulation in Titan&#8217;s stratosphere and mesosphere is dominated by a single pole-to-pole circulation cell for most of the Titan year (Hourdin et al., 1995; Newman et al., 2011; Lebonnois et al., 2012), and observations are broadly consistent with this prediction (Teanby et al., 2012, Vinatier et al., 2015). These models suggest circulation across the stratospheric equator, but this is not entirely consistent with what is observed. Existing studies show a North-South asymmetry in stratospheric haze abundance (Lorenz et al., 1997; de Kok et al., 2010), suggesting a mixing barrier near the equator. Here, we present a radiance ratio method for approximating latitudinal distributions of stratospheric HCN. We apply this to the region +/-30 degN and use HCN as a tracer to investigate the evolution and behaviour of the equatorial mixing barrier over the Cassini mission. 2.&#160; Observations The Cassini spacecraft explored Saturn and its moons from 2004 to 2017. Throughout its 13-year exploration, Cassini performed 127 close flybys of Titan, observing at infrared, visible and ultra-violet wavelengths. One of Cassini&#8217;s twelve instruments, the Composite Infrared Spectrometer (CIRS) (Flasar et al., 2004; Jennings et al., 2017; Nixon et al., 2019) collected almost 10 million Titan spectra in the mid and far-infrared ranges (10 &#8211; 1500 cm-1), at a varied spectral resolution between 0.5 &#8211; 15.5 cm-1. In this study, we analyse low spectral resolution (~15 cm-1) observations collected by two CIRS focal planes, sensitive to wavenumber ranges 600 &#8211; 1100 cm-1 (FP3) and 1100 &#8211; 1500 cm-1 (FP4). Generally, low spectral resolution observations require shorter scan times so can be performed at a closer approach distance to Titan, hence achieving higher spatial resolution. This allows small spatial variations in atmospheric constituents to be resolved. Low-resolution observations also have good coverage of Titan&#8217;s equatorial region throughout the entire Cassini mission (Figure 1). <img src="" alt="" width="337" height="262" /> Figure 1: Mission coverage for the Cassini CIRS low spectral resolution nadir mapping observations. 3.&#160; Optimising Line-by-Line Retrieval Efficiency Line-by-line (LBL) inversions in spectral analysis are computationally expensive. The correlated-k approximation (Lacis and Oinas, 1991) is often used to decrease the computation time of retrievals, but we found that it is not sufficiently accurate for these low spectral resolution and high signal-to-noise ratio observations (Figure 2c, d). In LBL modelling, a key parameter is the underlying spectral grid spacing. Finer grid spacing improves the forward model accuracy, but at a greater computation cost. To improve the efficiency of LBL runs, we determine a maximum grid spacing (Figure 2a, b) for which a LBL inversion will produce a sufficiently accurate spectrum in the shortest computation time. Typically, a single forward model run takes 2 hours for LBL, compared to 2 seconds for k-tables. <img src="" alt="" width="540" height="271" /> Figure 2: Comparison of spectra produced using a correlated-k (k-table) method and a line-by-line (LBL) method at varied spectral grid spacing. Maximum radiance difference (MRD) (a, b, blue line) between spectra produced at varied (0.1 &#8211; 0.0001 cm-1) and fine (0.0001 cm-1) grid spacing is assessed against a level of sufficient accuracy (a, b, grey area). The grid spacing determined to be optimal (0.001 cm-1 for FP3, 0.005 cm-1 for FP4) produces an almost identical spectrum to very fine (0.0001 cm-1) grid spacing (c, d) but at a significantly reduced runtime (a, b). A spectrum produced using a coarse grid spacing (0.1 cm-1) is shown for comparison. The spectrum retrieved using k-tables is not sufficiently accurate for these low-resolution observations (c, d). 4.&#160; Estimating Stratospheric HCN with a Radiance Ratio We construct a radiance ratio formula for approximating HCN abundance from CIRS spectra, such that a greater number of observations can be analysed rapidly. Radiance ratios can be a useful tool for approximating gas contributions to a spectrum. They do not have the reliability of full spectral retrievals but require significantly less computation time. We compare the radiance ratio latitude dependence to full LBL retrievals of HCN, for a subset of our observations, to assess the reliability of our ratio method. LBL retrievals are performed using the Nemesis radiative transfer and retrieval code (Irwin et al., 2008) with our pre-determined optimal grid spacing. We calculate the radiance ratio for a set of approximately 20 low spectral resolution mapping observations (3 are shown in Figure 3). There appears to be a sharp change in HCN abundance near the equator (Figure 3). This hints at a potential mixing barrier in Titan&#8217;s stratosphere. Furthermore, the position of this potential barrier appears to migrate over time. We use the results of this study to investigate dynamic processes in the equatorial region of Titan&#8217;s stratosphere and its evolution over the entire Cassini mission. <img src="" alt="" width="636" height="213" /> Figure 3: Our radiance ratio calculated for observations acquired on 08/2005 (a), 05/2006 (b) and 07/2012 (c). The radiance ratio is smoothed by fitting splines (Teanby, 2007). The gradient of each smoothed fit is also shown (bottom). Acknowledgements This research was funded by the UK Sciences and Technology Facilities Council. References de Kok, R., et al. (2010). https://doi.org/10.1016/j.icarus.2009.10.021 Flasar, F. M., et al. (2004). https://doi.org/10.1007/s11214-004-1454-9 Hourdin, F., et al. (1995). https://doi.org/10.1006/icar.1995.1162 Irwin, P., et al. (2008). https://doi.org/10.1016/j.jqsrt.2007.11.006 Jennings, D. E., et al. (2017). https://doi.org/10.1364/AO.56.005274 Lacis, A. A., & Oinas, V. (1991). https://doi.org/10.1029/90JD01945 Lebonnois, S., et al.&#160; (2012). https://doi.org/10.1016/j.icarus.2011.11.032 Lorenz, R. D., et al. (1997). https://doi.org/10.1006/icar.1997.5687 Newman, C. E., et al. (2011). https://doi.org/10.1016/j.icarus.2011.03.025 Nixon, C. A., et al. (2019). https://doi.org/10.3847/1538-4365/ab3799 Niemann, H. B., et al. (2005). https://doi.org/10.1038/nature04122 Teanby, N. A. (2007). https://doi.org/10.1007/s11004-007-9104-x Teanby, N. A., et al.&#160; (2012). https://doi.org/10.1038/nature1161 Vinatier, S., et al.&#160; (2015). https://doi.org/10.1016/j.icarus.2014.11.019

More details from the publisher

Uranus and Neptune in the Mid-Infrared: Recent Findings from VLT-VISIR and Future Opportunities with JWST-MIRI

(2022)

Authors:

Michael T Roman, Leigh N Fletcher, Glenn S Orton, Naomi Rowe-Gurney, Julianne Moses, Thomas K Greathouse, Patrick GJ Irwin, Yasumasa Kasaba, Takuya Fujiyoshi, Heidi B Hammel, Imke de Pater, Arrate Antunano, James Sinclair, Henrik Melin, Deborah Bardet

Abstract:

In this talk, we present highlights from our recent analyses of mid-infrared observations of Uranus and Neptune, and we look ahead to anticipated discoveries from the James Webb Space Telescope. &#160; Drawing from a combination of archival and recent ground-based imaging and spectroscopy, we examine the spatial structure and trends of mid-infrared emission from the ice giant atmospheres.&#160; We report on surprising temporal variability in the atmosphere of Neptune (see Figure 1) with an unexpected decline in stratospheric temperatures since at least 2003. &#160;Recent VLT-VISIR imaging and spectroscopy are presented, revealing how this trend has progressed. In contrast, we show that no evidence yet exists of long-term thermal changes in Uranus&#8217; stratosphere, but mid-IR observations of Uranus are still extremely limited. The observed spatial structure of Uranus&#8217; mid-infrared emission is intriguing (Figure 2), as it is inconsistent with simple models of the atmospheric circulation and/or chemistry and its physical interpretation remains unclear. We share recent observations from VLT-VISIR and express the need for continued ground-based imaging for both Uranus and Neptune. Finally, we discuss how the James Webb Space Telescope MIRI observations will help greatly advance our understanding of the ice giants in the years ahead. In particular, given its supreme sensitivity compared to ground-based observations, JWST-MIRI observations will resolve the nature of Uranus stratospheric thermal/chemical structure and reveal how temperature and chemical abundances change with the seasons in the atmospheres of both ice giants. &#160; <img src="" alt="" width="868" height="646" /> Figure 1: Observed changes in Neptune&#8217;s thermal-infrared brightness, a measure of temperature in Neptune&#8217;s atmosphere. The plot shows the relative change in the thermal-infrared brightness from Neptune&#8217;s stratosphere with time for all existing images taken by ground-based telescopes. Brighter images are interpreted as warmer. Corresponding thermal-infrared images (top) at wavelengths of ~12 &#181;m show Neptune&#8217;s appearance in 2006, 2009, 2018 (observed by the European Southern Observatory&#8217;s Very Large Telescope VISIR instrument), and 2020 (observed by Subaru&#8217;s COMICS instrument). The south pole appears to have become dramatically warmer in just the past few years.&#160; &#160; <img src="" alt="" /> Figure 2: Uranus' 13-micron images from VLT-VISIR in 2009 and 2018, with enhanced emission from high latitudes.&#160; From current ground-based observations alone, it is unclear whether the enhanced radiances are due to greater temperatures or enhance acetylene abundances, but JWST will solve this mystery.&#160; &#160;

More details from the publisher

Uranus and Neptune's stratospheric water abundance and external flux from Herschel-HIFI

(2022)

Authors:

Nicholas Teanby, Patrick Irwin, Conor Nixon, Martin Cordiner, Lucy Wright

Abstract:

Water vapour in the stratospheres of Uranus and Neptune has previously been shown to originate from external sources. These sources could include comet impacts [4], interplanetary dust particles [8], or rings and moons [1]. Stratospheric water was first detected on Uranus and Neptune by the Short-Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO) [2], but the uncertainties were relatively large due to lack of constraint on the vertical water profiles and relatively low spectral resolution of the observations. Here we present new observational constraints on Uranus&#8217; and Neptune&#8217;s externally sourced stratospheric water abundance using disc-averaged high spectral resolution observations of the 557 GHz water emission line from Herschel&#8217;s Heterodyne Instrument for the Far-Infrared (HIFI). On both planets the emission line is significantly broadened by disc-averaging of Doppler shifts from planetary rotation, which was carefully accounted for in our analysis [10]. Derived stratospheric column water abundances are 0.56+0.26-0.06 x 1014 cm-2&#160;for Uranus and 1.9+0.2-0.3 x 1014 cm-2 for Neptune. These results imply Neptune has about four times as much stratospheric water as Uranus, and are consistent with previous determinations from ISO-SWS and Herschel-PACS, but with improved precision. For Uranus excellent observational fits are obtained by scaling photochemical model profiles [3,7] or with step-type profiles with water vapor limited to <=0.6mbar. However, Uranus&#8217; cold stratospheric temperatures imply a ~0.03mbar condensation level, which further limits water vapor to pressures <=0.03 mbar. Neptune&#8217;s warmer stratosphere has a deeper ~1 mbar condensation level, so emission-line pressure broadening can be used to further constrain the water profile. For Neptune, excellent fits are obtained using step-type profiles with cutoffs of ~0.3-0.6 mbar or by scaling a photochemical model profile [7]. Step-type profiles with cutoffs >=1.0 mbar or <=0.1 mbar can be rejected with 4&#963; significance. Rescaling photochemical model profiles from [7] to match our observed column abundances implies similar external water fluxes for both planets: 8.3+4.0-0.9 x 104 cm-2s-1 for Uranus and 12.7+1.3-2.0 x 104 cm-2s-1 for Neptune. This inferred water influx rates suggest that Uranus and Neptune may in fact have very similar IDP fluxes, unless there are significant water-loss processes that are not accounted for in current photochemical models [3,7]. This is unexpected as the IDP flux on Neptune is expected to be higher due to its closer proximity to the Kuiper belt. For example, the dynamical model of [8] predicts that the flux of IDP grains is around seven times higher on Neptune than on Uranus, but model uncertainties are large enough so as not to preclude a similar flux. The comet impact rates on Uranus and Neptune are also predicted to be quite similar [5,11], so both planets may experience similar external flux processes. Our new analysis suggests that Neptune&#8217;s approximately four times greater observed water column abundance is primarily caused by its warmer stratosphere preventing loss by condensation, rather than by a significantly more intense external source. Larger error bars on the Uranus estimates are due to greater uncertainty in the high-altitude temperature profile. To reconcile these water fluxes with other observed stratospheric oxygen species (CO and CO2) requires either a significant CO component in interplanetary dust particles (Uranus) or contributions from cometary impacts (Uranus, Neptune). In particular, the large CO abundance in Neptune&#8217;s stratosphere suggests that we just happen to be observing Neptune at a time shortly after a large comet impact [4,6,9]. Further details of our results and analysis are available in our recent publication [10]. <img src="" alt="" width="1036" height="882" /> Fig1: Herschel-HIFI line-to-continuum ratio spectra of the 557GHz water line for HRS and WBS spectrometers. The water line is clearly visible at high signal to noise on both planets, but the line is broadened due to Doppler shift combined with the disc-broadened nature of the HIFI spectra. (Figure from https://doi.org/10.3847/PSJ/ac650f, see reference [10]). &#160; <img src="" alt="" width="1013" height="680" /> Fig2: Fits to Uranus and Neptune HIFI-HRS spectra 557GHz water line. (a,b) Uranus can be fitted with step profiles with a step pressure less than ~0.6mbar or by scaling photochemical profiles. However, significant water vapour is unlikely at pressures above ~0.03mbar due to saturation. (c,d) Neptune can be fitted with step profiles with a step in the pressure range 0.3-0.6mbar or by scaling photochemical profiles. (Figure from https://doi.org/10.3847/PSJ/ac650f, see reference [10]). References [1] Cavali&#233;+ 2019. https://ui.adsabs.harvard.edu/abs/2019A%26A...630A..87C/abstract [2] Feuchtgruber+ 1997. https://ui.adsabs.harvard.edu/abs/1997Natur.389..159F/abstract [3] Lara+ 2019. https://ui.adsabs.harvard.edu/abs/2019A%26A...621A.129L/abstract [4] Lellouch+ 2005. https://ui.adsabs.harvard.edu/abs/2005A%26A...430L..37L/abstract [5] Levison 2000. https://ui.adsabs.harvard.edu/abs/2000Icar..143..415L/abstract [6] Moreno+ 2017. https://ui.adsabs.harvard.edu/abs/2017A%26A...608L...5M/abstract [7] Moses+Poppe 2017. https://ui.adsabs.harvard.edu/abs/2017Icar..297...33M/abstract [8] Poppe 2016. https://ui.adsabs.harvard.edu/abs/2016Icar..264..369P/abstract [9] Teanby+ 2019. https://ui.adsabs.harvard.edu/abs/2019Icar..319...86T/abstract [10] Teanby+ 2022. https://ui.adsabs.harvard.edu/abs/2022PSJ.....3...96T/abstract [11] Zahnle 2003. https://ui.adsabs.harvard.edu/abs/2003Icar..163..263Z/abstract &#160;

More details from the publisher

Ground calibration of the Ariel space telescope: optical ground support equipment design and description

Proceedings of SPIE SPIE, the international society for optics and photonics 12180 (2022) 1218049-1218049-11

Authors:

Neil E Bowles, Manuel Abreu, Tim A van Kempen, Matthijs Krijger, Robert Spry, Rory Evans, Robert A Watkins, Cédric Pereira, E Pascale, Paul Eccleston, Chris Pearson, Lucile Desjonquères, Georgia Bishop, Andrew Caldwell, Andrea Moneti, Mauro Focardi, Subhajit Sarkar, Giuseppe Malaguti, Ioannis Argyriou, Keith Nowicki, Alexandre Cabral, Giovanna Tinetti

More details from the publisher

More details

Planetary atmosphere observation analysis

Research theme

Sub department

Preliminary atmospheric study of Jupiter using ISO/SWS data

Authors:

Abstract:

Stratospheric HCN and Evolution of a Mixing Barrier in Titan’s Equatorial Region from Low-Resolution Cassini/CIRS Spectra

Authors:

Abstract:

Uranus and Neptune in the Mid-Infrared: Recent Findings from VLT-VISIR and Future Opportunities with JWST-MIRI

Authors:

Abstract:

Uranus and Neptune's stratospheric water abundance and external flux from Herschel-HIFI

Authors:

Abstract:

Ground calibration of the Ariel space telescope: optical ground support equipment design and description

Authors:

FIND US

CONTACT US

Planetary atmosphere observation analysis

Research theme

Sub department

Related research groups

Preliminary atmospheric study of Jupiter using ISO/SWS data

Authors:

Abstract:

Stratospheric HCN and Evolution of a Mixing Barrier in Titan&#8217;s Equatorial Region from Low-Resolution Cassini/CIRS Spectra

Authors:

Abstract:

Uranus and Neptune in the Mid-Infrared: Recent Findings from VLT-VISIR and Future Opportunities with JWST-MIRI

Authors:

Abstract:

Uranus and Neptune's stratospheric water abundance and external flux from Herschel-HIFI

Authors:

Abstract:

Ground calibration of the Ariel space telescope: optical ground support equipment design and description

Authors:

Stratospheric HCN and Evolution of a Mixing Barrier in Titan’s Equatorial Region from Low-Resolution Cassini/CIRS Spectra