Spatial and seasonal variations in C_3/H_x hydrocarbon abundance in Titan's stratosphere from Cassini CIRS observations

Icarus 317 (2019) 454-469

NA Lombardo, CA Nixon, RK Achterberg, A Jolly, K Sung, PGJ Irwin, FM Flasar

© 2018 Of the C3Hxhydrocarbons, propane (C3H8) and propyne (methylacetylene, CH3C2H) were first detected in Titan's atmosphere during the Voyager 1 flyby in 1980. Propene (propylene, C3H6) was first detected in 2013 with data from the Composite InfraRed Spectrometer (CIRS) instrument on Cassini. We present the first measured abundance profiles of propene on Titan from radiative transfer modeling, and compare our measurements to predictions derived from several photochemical models. Near the equator, propene is observed to have a peak abundance of 10 ppbv at a pressure of 0.2 mbar. Several photochemical models predict the amount at this pressure to be in the range 0.3–1 ppbv and also show a local minimum near 0.2 mbar which we do not see in our measurements. We also see that propene follows a different latitudinal trend than the other C3molecules. While propane and propyne concentrate near the winter pole, transported via a global convective cell, propene is most abundant above the equator. We retrieve vertical abundances profiles between 125 km and 375 km for these gases for latitude averages between 60°S–20°S, 20°S–20°N, and 20°N–60°N over two time periods, 2004 through 2009 representing Titan's atmosphere before the 2009 equinox, and 2012 through 2015 representing time after the equinox. Additionally, using newly corrected line data, we determined an updated upper limit for allene (propadiene, CH2CCH2, the isomer of propyne). We claim a 3-σ upper limit mixing ratio of 2.5 × 10−9 within 30° of the equator. The measurements we present will further constrain photochemical models by refining reaction rates and the transport of these gases throughout Titan's atmosphere.

Spectral characterization of analog samples in anticipation of OSIRIS-REx's arrival at Bennu: A blind test study

Icarus 319 (2019) 701-723

KL Donaldson Hanna, DL Schrader, EA Cloutis, GD Cody, AJ King, TJ McCoy, DM Applin, JP Mann, NE Bowles, JR Brucato, HC Connolly, E Dotto, LP Keller, LF Lim, BE Clark, VE Hamilton, C Lantz, DS Lauretta, SS Russell, PF Schofield

© 2018 We present spectral measurements of a suite of mineral mixtures and meteorites that are possible analogs for asteroid (101955) Bennu, the target asteroid for NASA's Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) mission. The sample suite, which includes anhydrous and hydrated mineral mixtures and a suite of chondritic meteorites (CM, CI, CV, CR, and L5), was chosen to characterize the spectral effects due to varying amounts of aqueous alteration and minor amounts of organic material. Our results demonstrate the utility of mineral mixtures for understanding the mixing behavior of meteoritic materials and identifying spectrally dominant species across the visible to near-infrared (VNIR) and thermal infrared (TIR) spectral ranges. Our measurements demonstrate that, even with subtle signatures in the spectra of chondritic meteorites, we can identify diagnostic features related to the minerals comprising each of the samples. Also, the complementary nature of the two spectral ranges regarding their ability to detect different mixture and meteorite components can be used to characterize analog sample compositions better. However, we observe differences in the VNIR and TIR spectra between the mineral mixtures and the meteorites. These differences likely result from (1) differences in the types and physical disposition of constituents in the mixtures versus in meteorites, (2) missing phases observed in meteorites that we did not add to the mixtures, and (3) albedo differences among the samples. In addition to the initial characterization of the analog samples, we will use these spectral measurements to test phase detection and abundance determination algorithms in anticipation of mapping Bennu's surface properties and selecting a sampling site.

Neptune's carbon monoxide profile and phosphine upper limits from Herschel/SPIRE: Implications for interior structure and formation

Icarus 319 (2019) 86-98

NA Teanby, PGJ Irwin, JI Moses

© 2018 On Neptune, carbon monoxide and phosphine are disequilibrium species, and their abundance profiles can provide insights into interior processes and the external space environment. Here we use Herschel/SPIRE (Spectral and Photometric Imaging REceiver) observations from 14.9–51.5 cm-1to obtain abundances from multiple CO and PH3spectral features. For CO, we find that nine CO bands can be simultaneously fitted using a step profile with a 0.22 ppm tropospheric abundance, a 1.03 ppm stratospheric abundance, and a step transition pressure of 0.11 bar near the tropopause. This is in broad agreement with previous studies. However, we also find that the CO spectral features could be fitted, to well within measurement errors, with a profile that contains no tropospheric CO for pressure levels deeper than 0.5 bar, which is our preferred interpretation. This differs from previous studies that have assumed CO is well mixed throughout the troposphere, which would require an internal CO source to explain and a high O/H enrichment. Our interpretation removes the requirement for extreme interior O/H enrichment in thermochemical models and can finally reconcile D/H and CO measurements. If true, the lack of lower tropospheric CO would imply a decrease in Neptune's interior water content, favouring a silicate-rich instead of an ice-rich interior. This would be consistent with a protoplanetary ice source with a similar D/H ratio to the current solar system comet population. The upper tropospheric and stratospheric CO at pressures less than 0.5 bar could then be entirely externally sourced from a giant impact as suggested by Lellouch et al.(2005). We also derive a 3-σ upper limit for PH3of 1.1 ppb at 0.4–0.8 bar. This is the most stringent upper limit to-date and is entirely consistent with predictions from a simple photochemical model.

Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk

Astronomy and Astrophysics Springer Nature (2018)

A Müller, M Keppler, T Henning, M Samland, G Chauvin, H Beust, A-L Maire, K Molaverdikhani, R vanBoekel, M Benisty, A Boccaletti, M Bonnefoy, F Cantalloube, B Charnay, J-L Baudino, M Gennaro, ZC Long, A Cheetham, S Desidera, M Feldt, T Fusco, J Girard, R Gratton, J Hagelberg, M Janson, A-M Lagrange, M Langlois, C Lazzoni, R Ligi, F Menard, D Mesa, M Meyer, P Molliere, C Mordasini, T Moulin, A Pavlov, N Pawellek, SP Quanz, J Ramos, D Rouan, E Sissa, E Stadler, A Vigan, Z Wahhaj, L Weber, A Zurlo

Future of Venus Research and Exploration


LS Glaze, CF Wilson, LV Zasova, M Nakamura, S Limaye

The DREAMS Experiment Onboard the Schiaparelli Module of the ExoMars 2016 Mission: Design, Performances and Expected Results


F Esposito, S Debei, C Bettanini, C Molfese, I Arruego Rodriguez, G Colombatti, A-M Harri, F Montmessin, C Wilson, A Aboudan, P Schipani, L Marty, FJ Alvarez, V Apestigue, G Bellucci, J-J Berthelier, JR Brucato, SB Calcutt, S Chiodini, F Cortecchia, F Cozzolino, F Cucciarre, N Deniskina, G Deprez, G Di Achille, F Ferri, F Forget, G Franzese, E Friso, M Genzer, R Hassen-Kodja, H Haukka, M Hieta, JJ Jimenez, J-L Josset, H Kahanpaa, O Karatekin, G Landis, L Lapauw, R Lorenz, J Martinez-Oter, V Mennella, D Moehlmann, D Moirin, R Molinaro, T Nikkanen, E Palomba, MR Patel, J-P Pommereau, CI Popa, S Rafkin, P Rannou, NO Renno, J Rivas, W Schmidt, E Segato, S Silvestro, A Spiga, D Toledo, R Trautner, F Valero, L Vazquez, F Vivat, O Witasse, M Yela, R Mugnuolo, E Marchetti, S Pirrotta

Meat consumption, health, and the environment.

Science (New York, N.Y.) 361 (2018)

HCJ Godfray, P Aveyard, T Garnett, JW Hall, TJ Key, J Lorimer, RT Pierrehumbert, P Scarborough, M Springmann, SA Jebb

Both the global average per capita consumption of meat and the total amount of meat consumed are rising, driven by increasing average individual incomes and by population growth. The consumption of different types of meat and meat products has substantial effects on people's health, and livestock production can have major negative effects on the environment. Here, we explore the evidence base for these assertions and the options policy-makers have should they wish to intervene to affect population meat consumption. We highlight where more research is required and the great importance of integrating insights from the natural and social sciences.

Assessing the long-term variability of acetylene and ethane in the stratosphere of Jupiter

ICARUS 305 (2018) 301-313

H Melin, LN Fletcher, PT Donnelly, TK Greathouse, JH Lacy, GS Orton, RS Giles, JA Sinclair, PGJ Irwin

Exonephology: Transmission spectra from a 3D simulated cloudy atmosphere of HD 209458b

Monthly Notices of the Royal Astronomical Society 481 (2018) 194-205

S Lines, J Manners, NJ Mayne, J Goyal, AL Carter, IA Boutle, GKH Lee, C Helling, B Drummond, DM Acreman, DK Sing

© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. We present high-resolution transmission spectra, calculated directly from a 3D radiative hydrodynamic simulation that includes kinetic cloud formation, for HD 209458b. We find that the high opacity of our vertically extensive cloud deck, composed of a large number density of sub-μm particles, flattens the transmission spectrum and obscures spectral features identified in the observed data. We use the PANDEXO simulator to explore features of our HD 209458b spectrum which may be detectable with the James Webb Space Telescope. We determine that an 8-12μm absorption feature attributed to the mixed-composition, predominantly silicate cloud particles is a viable marker for the presence of cloud. Further calculations explore, and trends are identified with, variations in cloud opacity, composition heterogeneity, and artificially scaled gravitational settling on the transmission spectrum. Principally, by varying the upper extent of our cloud decks, rainout is identified to be a key process for the dynamical atmospheres of hot Jupiters and shown to dramatically alter the resulting spectrum. Our synthetic transmission spectra, obtained from the most complete, forward atmosphere simulations to date, allow us to explore the model's ability to conform with observations. Such comparisons can provide insight into the physical processes either missing or requiring improvement.

LRG-BEASTS III: ground-based transmission spectrum of the gas giant orbiting the cool dwarf WASP-80


J Kirk, PJ Wheatley, T Louden, I Skillen, GW King, J McCormac, PGJ Irwin

Venus Upper Clouds and the UV Absorber From MESSENGER/MASCS Observations


S Perez-Hoyos, A Sanchez-Lavega, A Garcia-Munoz, PGJ Irwin, J Peralta, G Holsclaw, WM McClintock, JF Sanz-Requena

A Chorus of the WindsOn Saturn!


PL Read

New spectro-photometric characterization of the substellar object HR2562B using SPHERE


D Mesa, J-L Baudino, B Charnay, V D'Orazi, S Desidera, A Boccaletti, R Gratton, M Bonnefoy, P Delorme, M Langlois, A Vigan, A Zurlo, A-L Maire, M Janson, J Antichi, A Baruffolo, P Bruno, E Cascone, G Chauvin, RU Claudi, V De Caprio, D Fantinel, G Farisato, M Feldt, E Giro, J Hagelberg, S Incorvaia, E Lagadec, A-M Lagrange, C Lazzoni, L Lessio, B Salasnich, S Scuderi, E Sissa, M Turatto

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

MEASUREMENT 122 (2018) 484-493

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

Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter


MA Lopez-Valverde, J-C Gerard, F Gonzalez-Galindo, A-C Vandaele, I Thomas, O Korablev, N Ignatiev, A Fedorova, F Montmessin, A Maattanen, S Guilbon, F Lefevre, MR Patel, S Jimenez-Monferrer, M Garcia-Comas, A Cardesin, CF Wilson, RT Clancy, A Kleinboehl, DJ McCleese, DM Kass, NM Schneider, MS Chaffin, JJ Lopez-Moreno, J Rodriguez

Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70


M Keppler, M Benisty, A Mueller, T Henning, R van Boekel, F Cantalloube, C Ginski, RG van Holstein, A-L Maire, A Pohl, M Samland, H Avenhaus, J-L Baudino, A Boccaletti, J de Boer, M Bonnefoy, G Chauvin, S Desidera, M Langlois, C Lazzoni, G-D Marleau, C Mordasini, N Pawellek, T Stolker, A Vigan, A Zurlo, T Birnstiel, W Brandner, M Feldt, M Flock, J Girard, R Gratton, J Hagelberg, A Isella, M Janson, A Juhasz, J Kemmer, Q Kral, A-M Lagrange, R Launhardt, A Matter, F Menard, J Milli, P Molliere, J Olofsson, L Perez, P Pinilla, C Pinte, SP Quanz, T Schmidt, S Udry, Z Wahhaj, JP Williams, E Buenzli, M Cudel, C Dominik, R Galicher, M Kasper, J Lannier, D Mesa, D Mouillet, S Peretti, C Perrot, G Salter, E Sissa, F Wildi, L Abe, J Antichi, J-C Augereau, A Baruffolo, P Baudoz, A Bazzon, J-L Beuzit, P Blanchard, SS Brems, T Buey, V De Caprio, M Carbillet, M Carle, E Cascone, A Cheetham, R Claudi, A Costille, A Delboulbe, K Dohlen, D Fantinel, P Feautrier, T Fusco, E Giro, L Gluck, C Gry, N Hubin, E Hugot, M Jaquet, D Le Mignant, M Llored, F Madec, Y Magnard, P Martinez, D Maurel, M Meyer, O Moeller-Nilsson, T Moulin, L Mugnier, A Origne, A Pavlov, D Perret, C Petit, J Pragt, P Puget, P Rabou, J Ramose, F Rigal, S Rochat, R Roelfsema, G Rousset, A Roux, B Salasnich, J-F Sauvage, A Sevin, C Soenke, E Stadler, M Suarez, M Turatto, L Weber

The GJ 504 system revisited. Combining interferometric, radial velocity, and high contrast imaging data

Astronomy and Astrophysics Springer Verlag (2018)

M Bonnefoy, K Perraut, A-M Lagrange, P Delorme, A Vigan, M Line, L Rodet, C Ginski, D Mourard, G-D Marleau, M Samland, P Tremblin, R Ligi, F Cantalloube, P Mollière, B Charnay, M Kuzuhara, M Janson, C Morley, DD Homeier, VD Orazi, H Klahr, C Mordasini, B Lavie, J-L Baudino, H Beust, S Peretti, A Musso Bartucci, D Mesa, B Bézard, A Boccaletti, R Galicher, J Hagelberg, S Desidera, B Biller, A-L Maire, F Allard, S Borgniet, J Lannier, N Meunier, M Desort, E Alecian, G Chauvin, M Langlois, T Henning, L Mugnier, D Mouillet, R Gratton, T Brandt, M Mc Elwain, J-L Beuzit, M Tamura, Y Hori, W Brandner, E Buenzli, A Cheetham, M Cudel, M Feldt, M Kasper, M Keppler, T Kopytova, M Meyer, C Perrot, D Rouan, G Salter, T Schmidt, E Sissa, F Wildi, P Blanchard, V De Caprio, A Delboulbé, D Maurel, T Moulin, A Pavlov, P Rabou, J Ramos, R Roelfsema, G Rousset, E Stadler, F Rigal, L Weber

Abundance Measurements of Titan’s Stratospheric HCN, HC3N, C3H4, and CH3CN from ALMA Observations

Icarus (2018)

A Thelen, C Nixon, C Nancy, M Cordiner, E Molter, N Teanby, PG IRWIN, J Serigano, S Charnley

A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex.

Nature communications 9 (2018) 3564-

LN Fletcher, GS Orton, JA Sinclair, S Guerlet, PL Read, A Antuñano, RK Achterberg, FM Flasar, PGJ Irwin, GL Bjoraker, J Hurley, BE Hesman, M Segura, N Gorius, A Mamoutkine, SB Calcutt

Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon-which was previously expected to be trapped in the troposphere-can influence the stratospheric temperatures some 300 km above Saturn's clouds.

Seasonal evolution of C2N2, C3H4, and C4H2 abundances in Titan's lower stratosphere


M Sylvestre, NA Teanby, S Vinatier, S Lebonnois, PGJ Irwin