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@comment{{Command line: /usr/bin/bib2bib --quiet -c 'not journal:"Discussions"' -c year=2015 -c $type="ARTICLE" -oc pub2015.txt -ob pub2015.bib}}
  author = {{Leconte}, J. and {Forget}, F. and {Lammer}, H.},
  title = {{On the (anticipated) diversity of terrestrial planet atmospheres}},
  journal = {Experimental Astronomy},
  keywords = {Planet, Atmosphere, Composition, Climate regime},
  year = 2015,
  volume = 40,
  pages = {449-467},
  abstract = {{On our way toward the characterization of smaller and more temperate
planets, missions dedicated to the spectroscopic observation of
exoplanets will teach us about the wide diversity of classes of
planetary atmospheres, many of them probably having no equivalent in the
Solar System. But what kind of atmospheres can we expect? To start
answering this question, many theoretical studies have tried to
understand and model the various processes controlling the formation and
evolution of planetary atmospheres, with some success in the Solar
System. Here, we shortly review these processes and we try to give an
idea of the various type of atmospheres that these processes can create.
As will be made clear, current atmosphere evolution models have many
shortcomings yet, and need heavy calibrations. With that in mind, we
will thus discuss how observations with a mission similar to EChO would
help us unravel the link between a planet's environment and its
  doi = {10.1007/s10686-014-9403-4},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Tinetti}, G. and {Drossart}, P. and {Eccleston}, P. and {Hartogh}, P. and 
	{Isaak}, K. and {Linder}, M. and {Lovis}, C. and {Micela}, G. and 
	{Ollivier}, M. and {Puig}, L. and {Ribas}, I. and {Snellen}, I. and 
	{Swinyard}, B. and {Allard}, F. and {Barstow}, J. and {Cho}, J. and 
	{Coustenis}, A. and {Cockell}, C. and {Correia}, A. and {Decin}, L. and 
	{de Kok}, R. and {Deroo}, P. and {Encrenaz}, T. and {Forget}, F. and 
	{Glasse}, A. and {Griffith}, C. and {Guillot}, T. and {Koskinen}, T. and 
	{Lammer}, H. and {Leconte}, J. and {Maxted}, P. and {Mueller-Wodarg}, I. and 
	{Nelson}, R. and {North}, C. and {Pallé}, E. and {Pagano}, I. and 
	{Piccioni}, G. and {Pinfield}, D. and {Selsis}, F. and {Sozzetti}, A. and 
	{Stixrude}, L. and {Tennyson}, J. and {Turrini}, D. and {Zapatero-Osorio}, M. and 
	{Beaulieu}, J.-P. and {Grodent}, D. and {Guedel}, M. and {Luz}, D. and 
	{N{\o}rgaard-Nielsen}, H.~U. and {Ray}, T. and {Rickman}, H. and 
	{Selig}, A. and {Swain}, M. and {Banaszkiewicz}, M. and {Barlow}, M. and 
	{Bowles}, N. and {Branduardi-Raymont}, G. and {du Foresto}, V.~C. and 
	{Gerard}, J.-C. and {Gizon}, L. and {Hornstrup}, A. and {Jarchow}, C. and 
	{Kerschbaum}, F. and {Kovacs}, G. and {Lagage}, P.-O. and {Lim}, T. and 
	{Lopez-Morales}, M. and {Malaguti}, G. and {Pace}, E. and {Pascale}, E. and 
	{Vandenbussche}, B. and {Wright}, G. and {Ramos Zapata}, G. and 
	{Adriani}, A. and {Azzollini}, R. and {Balado}, A. and {Bryson}, I. and 
	{Burston}, R. and {Colomé}, J. and {Crook}, M. and {Di Giorgio}, A. and 
	{Griffin}, M. and {Hoogeveen}, R. and {Ottensamer}, R. and {Irshad}, R. and 
	{Middleton}, K. and {Morgante}, G. and {Pinsard}, F. and {Rataj}, M. and 
	{Reess}, J.-M. and {Savini}, G. and {Schrader}, J.-R. and {Stamper}, R. and 
	{Winter}, B. and {Abe}, L. and {Abreu}, M. and {Achilleos}, N. and 
	{Ade}, P. and {Adybekian}, V. and {Affer}, L. and {Agnor}, C. and 
	{Agundez}, M. and {Alard}, C. and {Alcala}, J. and {Allende Prieto}, C. and 
	{Alonso Floriano}, F.~J. and {Altieri}, F. and {Alvarez Iglesias}, C.~A. and 
	{Amado}, P. and {Andersen}, A. and {Aylward}, A. and {Baffa}, C. and 
	{Bakos}, G. and {Ballerini}, P. and {Banaszkiewicz}, M. and 
	{Barber}, R.~J. and {Barrado}, D. and {Barton}, E.~J. and {Batista}, V. and 
	{Bellucci}, G. and {Belmonte Avilés}, J.~A. and {Berry}, D. and 
	{Bézard}, B. and {Biondi}, D. and {B{\l}{\c e}cka}, M. and 
	{Boisse}, I. and {Bonfond}, B. and {Bordé}, P. and {B{\"o}rner}, P. and 
	{Bouy}, H. and {Brown}, L. and {Buchhave}, L. and {Budaj}, J. and 
	{Bulgarelli}, A. and {Burleigh}, M. and {Cabral}, A. and {Capria}, M.~T. and 
	{Cassan}, A. and {Cavarroc}, C. and {Cecchi-Pestellini}, C. and 
	{Cerulli}, R. and {Chadney}, J. and {Chamberlain}, S. and {Charnoz}, S. and 
	{Christian Jessen}, N. and {Ciaravella}, A. and {Claret}, A. and 
	{Claudi}, R. and {Coates}, A. and {Cole}, R. and {Collura}, A. and 
	{Cordier}, D. and {Covino}, E. and {Danielski}, C. and {Damasso}, M. and 
	{Deeg}, H.~J. and {Delgado-Mena}, E. and {Del Vecchio}, C. and 
	{Demangeon}, O. and {De Sio}, A. and {De Wit}, J. and {Dobrijévic}, M. and 
	{Doel}, P. and {Dominic}, C. and {Dorfi}, E. and {Eales}, S. and 
	{Eiroa}, C. and {Espinoza Contreras}, M. and {Esposito}, M. and 
	{Eymet}, V. and {Fabrizio}, N. and {Fern{\'a}ndez}, M. and {Femen{\'{\i}}a Castella}, B. and 
	{Figueira}, P. and {Filacchione}, G. and {Fletcher}, L. and 
	{Focardi}, M. and {Fossey}, S. and {Fouqué}, P. and {Frith}, J. and 
	{Galand}, M. and {Gambicorti}, L. and {Gaulme}, P. and {Garc{\'{\i}}a L{\'o}pez}, R.~J. and 
	{Garcia-Piquer}, A. and {Gear}, W. and {Gerard}, J.-C. and {Gesa}, L. and 
	{Giani}, E. and {Gianotti}, F. and {Gillon}, M. and {Giro}, E. and 
	{Giuranna}, M. and {Gomez}, H. and {Gomez-Leal}, I. and {Gonzalez Hernandez}, J. and 
	{Gonz{\'a}lez Merino}, B. and {Graczyk}, R. and {Grassi}, D. and 
	{Guardia}, J. and {Guio}, P. and {Gustin}, J. and {Hargrave}, P. and 
	{Haigh}, J. and {Hébrard}, E. and {Heiter}, U. and {Heredero}, R.~L. and 
	{Herrero}, E. and {Hersant}, F. and {Heyrovsky}, D. and {Hollis}, M. and 
	{Hubert}, B. and {Hueso}, R. and {Israelian}, G. and {Iro}, N. and 
	{Irwin}, P. and {Jacquemoud}, S. and {Jones}, G. and {Jones}, H. and 
	{Justtanont}, K. and {Kehoe}, T. and {Kerschbaum}, F. and {Kerins}, E. and 
	{Kervella}, P. and {Kipping}, D. and {Koskinen}, T. and {Krupp}, N. and 
	{Lahav}, O. and {Laken}, B. and {Lanza}, N. and {Lellouch}, E. and 
	{Leto}, G. and {Licandro Goldaracena}, J. and {Lithgow-Bertelloni}, C. and 
	{Liu}, S.~J. and {Lo Cicero}, U. and {Lodieu}, N. and {Lognonné}, P. and 
	{Lopez-Puertas}, M. and {Lopez-Valverde}, M.~A. and {Lundgaard Rasmussen}, I. and 
	{Luntzer}, A. and {Machado}, P. and {MacTavish}, C. and {Maggio}, A. and 
	{Maillard}, J.-P. and {Magnes}, W. and {Maldonado}, J. and {Mall}, U. and 
	{Marquette}, J.-B. and {Mauskopf}, P. and {Massi}, F. and {Maurin}, A.-S. and 
	{Medvedev}, A. and {Michaut}, C. and {Miles-Paez}, P. and {Montalto}, M. and 
	{Monta{\~n}és Rodr{\'{\i}}guez}, P. and {Monteiro}, M. and 
	{Montes}, D. and {Morais}, H. and {Morales}, J.~C. and {Morales-Calder{\'o}n}, M. and 
	{Morello}, G. and {Moro Mart{\'{\i}}n}, A. and {Moses}, J. and 
	{Moya Bedon}, A. and {Murgas Alcaino}, F. and {Oliva}, E. and 
	{Orton}, G. and {Palla}, F. and {Pancrazzi}, M. and {Pantin}, E. and 
	{Parmentier}, V. and {Parviainen}, H. and {Pe{\~n}a Ram{\'{\i}}rez}, K.~Y. and 
	{Peralta}, J. and {Perez-Hoyos}, S. and {Petrov}, R. and {Pezzuto}, S. and 
	{Pietrzak}, R. and {Pilat-Lohinger}, E. and {Piskunov}, N. and 
	{Prinja}, R. and {Prisinzano}, L. and {Polichtchouk}, I. and 
	{Poretti}, E. and {Radioti}, A. and {Ramos}, A.~A. and {Rank-L{\"u}ftinger}, T. and 
	{Read}, P. and {Readorn}, K. and {Rebolo L{\'o}pez}, R. and 
	{Rebord{\~a}o}, J. and {Rengel}, M. and {Rezac}, L. and {Rocchetto}, M. and 
	{Rodler}, F. and {S{\'a}nchez Béjar}, V.~J. and {Sanchez Lavega}, A. and 
	{Sanrom{\'a}}, E. and {Santos}, N. and {Sanz Forcada}, J. and 
	{Scandariato}, G. and {Schmider}, F.-X. and {Scholz}, A. and 
	{Scuderi}, S. and {Sethenadh}, J. and {Shore}, S. and {Showman}, A. and 
	{Sicardy}, B. and {Sitek}, P. and {Smith}, A. and {Soret}, L. and 
	{Sousa}, S. and {Stiepen}, A. and {Stolarski}, M. and {Strazzulla}, G. and 
	{Tabernero}, H.~M. and {Tanga}, P. and {Tecsa}, M. and {Temple}, J. and 
	{Terenzi}, L. and {Tessenyi}, M. and {Testi}, L. and {Thompson}, S. and 
	{Thrastarson}, H. and {Tingley}, B.~W. and {Trifoglio}, M. and 
	{Mart{\'{\i}}n Torres}, J. and {Tozzi}, A. and {Turrini}, D. and 
	{Varley}, R. and {Vakili}, F. and {de Val-Borro}, M. and {Valdivieso}, M.~L. and 
	{Venot}, O. and {Villaver}, E. and {Vinatier}, S. and {Viti}, S. and 
	{Waldmann}, I. and {Waltham}, D. and {Ward-Thompson}, D. and 
	{Waters}, R. and {Watkins}, C. and {Watson}, D. and {Wawer}, P. and 
	{Wawrzaszk}, A. and {White}, G. and {Widemann}, T. and {Winek}, W. and 
	{Wi{\'s}niowski}, T. and {Yelle}, R. and {Yung}, Y. and {Yurchenko}, S.~N.
  title = {{The EChO science case}},
  journal = {Experimental Astronomy},
  archiveprefix = {arXiv},
  eprint = {1502.05747},
  primaryclass = {astro-ph.EP},
  keywords = {Exoplanets, Spectroscopy, Atmospheric science, IR astronomy, Space missions},
  year = 2015,
  volume = 40,
  pages = {329-391},
  abstract = {{The discovery of almost two thousand exoplanets has revealed an
unexpectedly diverse planet population. We see gas giants in few-day
orbits, whole multi-planet systems within the orbit of Mercury, and new
populations of planets with masses between that of the Earth and
Neptune{\mdash}all unknown in the Solar System. Observations to date have
shown that our Solar System is certainly not representative of the
general population of planets in our Milky Way. The key science
questions that urgently need addressing are therefore: What are
exoplanets made of? Why are planets as they are? How do planetary
systems work and what causes the exceptional diversity observed as
compared to the Solar System? The EChO (Exoplanet Characterisation
Observatory) space mission was conceived to take up the challenge to
explain this diversity in terms of formation, evolution, internal
structure and planet and atmospheric composition. This requires in-depth
spectroscopic knowledge of the atmospheres of a large and well-defined
planet sample for which precise physical, chemical and dynamical
information can be obtained. In order to fulfil this ambitious
scientific program, EChO was designed as a dedicated survey mission for
transit and eclipse spectroscopy capable of observing a large, diverse
and well-defined planet sample within its 4-year mission lifetime. The
transit and eclipse spectroscopy method, whereby the signal from the
star and planet are differentiated using knowledge of the planetary
ephemerides, allows us to measure atmospheric signals from the planet at
levels of at least 10$^{-4}$ relative to the star. This can only
be achieved in conjunction with a carefully designed stable payload and
satellite platform. It is also necessary to provide broad instantaneous
wavelength coverage to detect as many molecular species as possible, to
probe the thermal structure of the planetary atmospheres and to correct
for the contaminating effects of the stellar photosphere. This requires
wavelength coverage of at least 0.55 to 11 {$\mu$}m with a goal of covering
from 0.4 to 16 {$\mu$}m. Only modest spectral resolving power is needed,
with R \~{} 300 for wavelengths less than 5 {$\mu$}m and R \~{} 30 for
wavelengths greater than this. The transit spectroscopy technique means
that no spatial resolution is required. A telescope collecting area of
about 1 m$^{2}$ is sufficiently large to achieve the necessary
spectro-photometric precision: for the Phase A study a 1.13
m$^{2}$ telescope, diffraction limited at 3 {$\mu$}m has been
adopted. Placing the satellite at L2 provides a cold and stable thermal
environment as well as a large field of regard to allow efficient
time-critical observation of targets randomly distributed over the sky.
EChO has been conceived to achieve a single goal: exoplanet
spectroscopy. The spectral coverage and signal-to-noise to be achieved
by EChO, thanks to its high stability and dedicated design, would be a
game changer by allowing atmospheric composition to be measured with
unparalleled exactness: at least a factor 10 more precise and a factor
10 to 1000 more accurate than current observations. This would enable
the detection of molecular abundances three orders of magnitude lower
than currently possible and a fourfold increase from the handful of
molecules detected to date. Combining these data with estimates of
planetary bulk compositions from accurate measurements of their radii
and masses would allow degeneracies associated with planetary interior
modelling to be broken, giving unique insight into the interior
structure and elemental abundances of these alien worlds. EChO would
allow scientists to study exoplanets both as a population and as
individuals. The mission can target super-Earths, Neptune-like, and
Jupiter-like planets, in the very hot to temperate zones (planet
temperatures of 300-3000 K) of F to M-type host stars. The EChO core
science would be delivered by a three-tier survey. The EChO Chemical
Census: This is a broad survey of a few-hundred exoplanets, which allows
us to explore the spectroscopic and chemical diversity of the exoplanet
population as a whole. The EChO Origin: This is a deep survey of a
subsample of tens of exoplanets for which significantly higher signal to
noise and spectral resolution spectra can be obtained to explain the
origin of the exoplanet diversity (such as formation mechanisms,
chemical processes, atmospheric escape). The EChO Rosetta Stones: This
is an ultra-high accuracy survey targeting a subsample of select
exoplanets. These will be the bright ``benchmark'' cases for which a large
number of measurements would be taken to explore temporal variations,
and to obtain two and three dimensional spatial information on the
atmospheric conditions through eclipse-mapping techniques. If EChO were
launched today, the exoplanets currently observed are sufficient to
provide a large and diverse sample. The Chemical Census survey would
consist of $\gt$ 160 exoplanets with a range of planetary sizes,
temperatures, orbital parameters and stellar host properties.
Additionally, over the next 10 years, several new ground- and
space-based transit photometric surveys and missions will come on-line
(e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on
finding bright, nearby systems. The current rapid rate of discovery
would allow the target list to be further optimised in the years prior
to EChO's launch and enable the atmospheric characterisation of hundreds
of planets.
  doi = {10.1007/s10686-015-9484-8},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Gonz{\'a}lez-Galindo}, F. and {L{\'o}pez-Valverde}, M.~A. and 
	{Forget}, F. and {Garc{\'{\i}}a-Comas}, M. and {Millour}, E. and 
	{Montabone}, L.},
  title = {{Variability of the Martian thermosphere during eight Martian years as simulated by a ground-to-exosphere global circulation model}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars, exobase, temperatures, variability, GCM},
  year = 2015,
  volume = 120,
  pages = {2020-2035},
  abstract = {{Using a ground-to-exosphere general circulation model for Mars we have
simulated the variability of the dayside temperatures at the exobase
during eight Martian years (MY, from MY24 to MY31, approximately from
1998 to 2013), taking into account the observed day-to-day solar and
dust load variability. We show that the simulated temperatures are in
good agreement with the exospheric temperatures derived from Precise
Orbit Determination of Mars Global Surveyor. We then study the effects
of the solar variability and of two planetary-encircling dust storms on
the simulated temperatures. The seasonal effect produced by the large
eccentricity of the Martian orbit translates in an
aphelion-to-perihelion temperature contrast in every simulated year.
However, the magnitude of this seasonal temperature variation is
strongly affected by the solar conditions, ranging from 50 K for years
corresponding to solar minimum conditions to almost 140 K during the
last solar maximum. The 27 day solar rotation cycle is observed on the
simulated temperatures at the exobase, with average amplitude of the
temperature oscillation of 2.6 K but with a significant interannual
variability. These two results highlight the importance of taking into
account the solar variability when simulating the Martian upper
atmosphere and likely have important implications concerning the
atmospheric escape rate. We also show that the global dust storms in
MY25 and MY28 have a significant effect on the simulated temperatures.
In general, they increase the exospheric temperatures over the low
latitude and midlatitude regions and decrease them in the polar regions.
  doi = {10.1002/2015JE004925},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Kerber}, L. and {Forget}, F. and {Wordsworth}, R.},
  title = {{Sulfur in the early martian atmosphere revisited: Experiments with a 3-D Global Climate Model}},
  journal = {\icarus},
  keywords = {Mars, climate, Volcanism, Atmospheres, evolution, Atmospheres, composition, Mars, atmosphere},
  year = 2015,
  volume = 261,
  pages = {133-148},
  abstract = {{Volcanic SO$_{2}$ in the martian atmosphere has been invoked as a
way to create a sustained or transient greenhouse during early martian
history. Many modeling studies have been performed to test the
feasibility of this hypothesis, resulting in a range of conclusions,
from highly feasible to highly improbable. In this study we perform a
wide range of simulations using the 3-D Laboratoire de
Météorologie Dynamique Generic Global Climate Model (GCM)
in order to place earlier results into context and to explore the
sensitivity of model outcomes to parameters such as SO$_{2}$
mixing ratio, atmospheric H$_{2}$O content, background atmospheric
pressure, and aerosol size, abundance, and composition. We conclude that
SO$_{2}$ is incapable of creating a sustained greenhouse on early
Mars, and that even in the absence of aerosols, local and daily
temperatures rise above 273 K for only for limited periods with
favorable background CO$_{2}$ pressures. In the presence of even
small amounts of aerosols, the surface is dramatically cooled for
realistic aerosol sizes. Brief, mildly warm conditions require the
co-occurrence of many improbable factors, while cooling is achieved for
a wide range of model parameters. Instead of causing warming, sulfur in
the martian atmosphere may have caused substantial cooling, leading to
the end of clement climate conditions on early Mars.
  doi = {10.1016/j.icarus.2015.08.011},
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  author = {{Sylvestre}, M. and {Guerlet}, S. and {Fouchet}, T. and {Spiga}, A. and 
	{Flasar}, F.~M. and {Hesman}, B. and {Bjoraker}, G.~L.},
  title = {{Seasonal changes in Saturn's stratosphere inferred from Cassini/CIRS limb observations}},
  journal = {\icarus},
  keywords = {Saturn, atmosphere, Atmospheres, composition, evolution, Infrared observations},
  year = 2015,
  volume = 258,
  pages = {224-238},
  abstract = {{We present temperature and hydrocarbons abundances
(C$_{2}$H$_{6}$, C$_{2}$H$_{2}$,
C$_{3}$H$_{8}$) retrieved from Cassini/CIRS limb spectra,
acquired during northern spring in 2010 (L$_{S}$ = 12 {\deg}) and
2012 (L$_{S}$ = 31 {\deg}). We compare them to the previous limb
measurements performed by Guerlet et al. (Guerlet, S. et al. [2009].
Icarus 203, 214-232) during northern winter. The latitudinal coverage
(from 79{\deg}N to 70{\deg}S) and the sensitivity of our observations to a
broad range of pressure levels (from 20 hPa to 0.003 hPa) allow us to
probe the meridional and vertical structure of Saturn's stratosphere
during northern spring. Our results show that in the northern
hemisphere, the lower stratosphere (1 hPa) has experienced the strongest
warming from northern winter to spring (11
{\plusmn}$_{0.9}$$^{1.1}$  K), while the southern hemisphere
exhibits weak variations of temperature at the same pressure level. We
investigate the radiative contribution in the thermal seasonal evolution
by comparing these results to the radiative-convective model of Guerlet
et al. (Guerlet, S. et al. [2014]. Icarus 238, 110-124). We show that
radiative heating and cooling by atmospheric minor constituents is not
always sufficient to reproduce the measured variations of temperature
(depending on the pressure level). The measurements of the hydrocarbons
abundances and their comparison with the predictions of the 1D
photochemical model of Moses and Greathouse (Moses, J.I., Greathouse,
T.K. [2005]. J. Geophys. Res. (Planets) 110, 9007) give insights into
large scale atmospheric dynamics. At 1 hPa, C$_{2}$H$_{6}$,
C$_{2}$H$_{2}$, and C$_{3}$H$_{8}$ abundances
are remarkably constant from northern winter to spring. At the same
pressure level, C$_{2}$H$_{6}$ and
C$_{3}$H$_{8}$ exhibit homogeneous meridional distributions
unpredicted by this photochemical model, unlike
C$_{2}$H$_{2}$. This is consistent with the existence of a
meridional circulation at 1 hPa, as suggested by previous studies.
  doi = {10.1016/j.icarus.2015.05.025},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Guerlet}, S. and {Fouchet}, T. and {Vinatier}, S. and {Simon}, A.~A. and 
	{Dartois}, E. and {Spiga}, A.},
  title = {{Stratospheric benzene and hydrocarbon aerosols detected in Saturn's auroral regions}},
  journal = {\aap},
  keywords = {planets and satellites: gaseous planets, planets and satellites: atmospheres, planets and satellites: composition, planets and satellites: aurorae},
  year = 2015,
  volume = 580,
  eid = {A89},
  pages = {A89},
  abstract = {{Context. Saturn's polar upper atmosphere exhibits significant auroral
activity; however, its impact on stratospheric chemistry (i.e. the
production of benzene and heavier hydrocarbons) and thermal structure
remains poorly documented. 
Aims: We aim to bring new constraints on the benzene distribution in Saturn's stratosphere, to characterize polar aerosols (their vertical distribution, composition, thermal infrared optical properties), and to quantify the aerosols' radiative impact on the thermal structure.
Methods: Infrared spectra acquired by the Composite Infrared Spectrometer (CIRS) on board Cassini in limb viewing geometry are analysed to derive benzene column abundances and aerosol opacity profiles over the 3 to 0.1 mbar pressure range. The spectral dependency of the haze opacity is assessed in the ranges 680-900 and 1360-1440 cm$^{-1}$. Then, a radiative climate model is used to compute equilibrium temperature profiles, with and without haze, given the haze properties derived from CIRS measurements.
Results: On Saturn's auroral region (80{\deg}S), benzene is found to be slightly enhanced compared to its equatorial and mid-latitude values. This contrasts with the Moses {\amp} Greathouse (2005, J. Geophys. Res., 110, 9007) photochemical model, which predicts a benzene abundance 50 times lower at 80{\deg}S than at the equator. This advocates for the inclusion of ion-related reactions in Saturn's chemical models. The polar stratosphere is also enriched in aerosols, with spectral signatures consistent with vibration modes assigned to aromatic and aliphatic hydrocarbons, and presenting similarities with the signatures observed in Titan's stratosphere. The aerosol mass loading at 80{\deg}S is estimated to be 1-4 {\times} 10$^{-5}$ g cm$^{-2}$, an order of magnitude less than on Jupiter, which is consistent with the order of magnitude weaker auroral power at Saturn. We estimate that this polar haze warms the middle stratosphere by 6 K in summer and cools the upper stratosphere by 5 K in winter. Hence, aerosols linked with auroral activity can partly account for the warm polar hood observed in Saturn's summer stratosphere. }}, doi = {10.1051/0004-6361/201424745}, adsurl = {}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }
  author = {{Brothers}, T.~C. and {Holt}, J.~W. and {Spiga}, A.},
  title = {{Planum Boreum basal unit topography, Mars: Irregularities and insights from SHARAD}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars, radar, basal unit, Planum Boreum, NPLD, ice},
  year = 2015,
  volume = 120,
  pages = {1357-1375},
  abstract = {{Shallow Radar investigations of Planum Boreum, Mars' ``basal unit'' (BU)
deposit have revealed multiple reentrants, morphologic irregularities,
and thickness trends that differ from those of the overlying north polar
layered deposits. We present detailed subsurface maps for these features
and offer explanation for genesis of the deposit's morphologic
asymmetry, expressed in different erosional characteristics between
0{\deg}E-180{\deg}E and 180{\deg}E-360{\deg}E. Additionally, this work
revealed a depression in the basal unit that may have provided a site
for spiral trough initiation. Interpretations of the findings suggest
that antecedent BU topography has a marked impact on modern morphology
and that aeolian forces have been the dominant driver of polar deposit
accumulation since at least the end of rupes unit emplacement. We find
no results requiring explanation beyond common Martian surface
processes, including aeolian erosion and impact armoring. To add to the
detailed morphologic study of the BU, we mapped the variability of the
BU radar reflection character. Combining generalized katabatic wind flow
with the radar mapping results suggests that rupes unit material sourced
the younger cavi. We present clear evidence that, while compositionally
distinct from the overlying layered deposits, the BU and its morphology
are intimately linked to the morphology of the north polar layered
deposits. Combining geologic evidence with paleoclimate modeling, the
deposits contain evidence for a long history of aeolian emplacement and
  doi = {10.1002/2015JE004830},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Smith}, I.~B. and {Spiga}, A. and {Holt}, J.~W.},
  title = {{Aeolian processes as drivers of landform evolution at the South Pole of Mars}},
  journal = {Geomorphology},
  keywords = {Mars, Polar, Ice, Winds, Clouds, Radar},
  year = 2015,
  volume = 240,
  pages = {54-69},
  abstract = {{We combine observations of surface morphology, topography, subsurface
stratigraphy, and near surface clouds with mesoscale simulations of
south polar winds and temperature to investigate processes governing the
evolution of spiral troughs on the South Pole of Mars. In general we
find that the south polar troughs are cyclic steps that all formed
during an erosional period, contrary to the troughs at the North Pole,
which are constructional features. The Shallow Radar instrument (SHARAD)
onboard Mars Reconnaissance Orbiter detects subsurface stratigraphy
indicating relatively recent accumulation that occurred post trough
formation in many locations. Using optical instruments, especially the
Thermal Emission Imaging System (THEMIS), we find low altitude trough
clouds in over 500 images spanning 6 Mars years. The locations of
detected clouds correspond to where recent accumulation is detected by
SHARAD, and offers clues about surface evolution. The clouds migrate by
season, moving poleward from 71{\deg} S at \~{} L$_{s}$ 200{\deg} until
L$_{s}$ 318{\deg}, when the last cloud is detected. Our atmospheric
simulations find that the fastest winds on the pole are found roughly
near the external boundary of the seasonal CO$_{2}$ ice cap. Thus,
we find that the migration of clouds (and katabatic jumps) corresponds
spatially to the retreat of the CO$_{2}$ seasonal ice as detected
by Titus (2005) and that trough morphology, through recent accumulation,
is integrally related to this seasonal retreat.
  doi = {10.1016/j.geomorph.2014.08.026},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Buchwitz}, M. and {Reuter}, M. and {Schneising}, O. and {Boesch}, H. and 
	{Guerlet}, S. and {Dils}, B. and {Aben}, I. and {Armante}, R. and 
	{Bergamaschi}, P. and {Blumenstock}, T. and {Bovensmann}, H. and 
	{Brunner}, D. and {Buchmann}, B. and {Burrows}, J.~P. and {Butz}, A. and 
	{Chédin}, A. and {Chevallier}, F. and {Crevoisier}, C.~D. and 
	{Deutscher}, N.~M. and {Frankenberg}, C. and {Hase}, F. and 
	{Hasekamp}, O.~P. and {Heymann}, J. and {Kaminski}, T. and {Laeng}, A. and 
	{Lichtenberg}, G. and {De Mazière}, M. and {Noël}, S. and 
	{Notholt}, J. and {Orphal}, J. and {Popp}, C. and {Parker}, R. and 
	{Scholze}, M. and {Sussmann}, R. and {Stiller}, G.~P. and {Warneke}, T. and 
	{Zehner}, C. and {Bril}, A. and {Crisp}, D. and {Griffith}, D.~W.~T. and 
	{Kuze}, A. and {O'Dell}, C. and {Oshchepkov}, S. and {Sherlock}, V. and 
	{Suto}, H. and {Wennberg}, P. and {Wunch}, D. and {Yokota}, T. and 
	{Yoshida}, Y.},
  title = {{The Greenhouse Gas Climate Change Initiative (GHG-CCI): Comparison and quality assessment of near-surface-sensitive satellite-derived CO2 and CH4 global data sets}},
  journal = {Remote Sensing of Environment},
  year = 2015,
  volume = 162,
  pages = {344-362},
  doi = {10.1016/j.rse.2013.04.024},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Wordsworth}, R.~D. and {Kerber}, L. and {Pierrehumbert}, R.~T. and 
	{Forget}, F. and {Head}, J.~W.},
  title = {{Comparison of ``warm and wet'' and ``cold and icy'' scenarios for early Mars in a 3-D climate model}},
  journal = {Journal of Geophysical Research (Planets)},
  archiveprefix = {arXiv},
  eprint = {1506.04817},
  primaryclass = {astro-ph.EP},
  keywords = {paleoclimate, early Mars, atmospheres, hydrology, valley networks, astrobiology},
  year = 2015,
  volume = 120,
  pages = {1201-1219},
  abstract = {{We use a 3-D general circulation model to compare the primitive Martian
hydrological cycle in ``warm and wet'' and ``cold and icy'' scenarios. In
the warm and wet scenario, an anomalously high solar flux or intense
greenhouse warming artificially added to the climate model are required
to maintain warm conditions and an ice-free northern ocean.
Precipitation shows strong surface variations, with high rates around
Hellas basin and west of Tharsis but low rates around Margaritifer Sinus
(where the observed valley network drainage density is nonetheless
high). In the cold and icy scenario, snow migration is a function of
both obliquity and surface pressure, and limited episodic melting is
possible through combinations of seasonal, volcanic, and impact forcing.
At surface pressures above those required to avoid atmospheric collapse
({\tilde}0.5 bar) and moderate to high obliquity, snow is transported to
the equatorial highland regions where the concentration of valley
networks is highest. Snow accumulation in the Aeolis quadrangle is high,
indicating an ice-free northern ocean is not required to supply water to
Gale crater. At lower surface pressures and obliquities, both
H$_{2}$O and CO$_{2}$ are trapped as ice at the poles and
the equatorial regions become extremely dry. The valley network
distribution is positively correlated with snow accumulation produced by
the cold and icy simulation at 41.8$^{}$ obliquity but
uncorrelated with precipitation produced by the warm and wet simulation.
Because our simulations make specific predictions for precipitation
patterns under different climate scenarios, they motivate future
targeted geological studies.
  doi = {10.1002/2015JE004787},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lebonnois}, S. and {Eymet}, V. and {Lee}, C. and {Vatant d'Ollone}, J.
  title = {{Analysis of the radiative budget of the Venusian atmosphere based on infrared Net Exchange Rate formalism}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Venus atmosphere, radiative transfer, Net Exchange Rate analysis},
  year = 2015,
  volume = 120,
  pages = {1186-1200},
  abstract = {{A detailed one-dimensional analysis of the energy balance in Venus
atmosphere is proposed in this work, based on the Net Exchange Rate
formalism that allows the identification in each altitude region of the
dominant energy exchanges controlling the temperature. Well-known
parameters that control the temperature profile are the solar flux
deposition and the cloud particle distribution. Balance between solar
heating and infrared energy exchanges is analyzed for each region: upper
atmosphere (from cloud top to 100 km), upper cloud, middle cloud, cloud
base, and deep atmosphere (cloud base to surface). The energy
accumulated below the clouds is transferred to the cloud base through
infrared windows, mostly at 3-4 {$\mu$}m and 5-7 {$\mu$}m. The continuum
opacity in these spectral regions is not well known for the hot
temperatures and large pressures of Venus's deep atmosphere but strongly
affects the temperature profile from cloud base to surface. From cloud
base, upward transport of energy goes through convection and short-range
radiative exchanges up to the middle cloud where the atmosphere is thin
enough in the 20-30 {$\mu$}m window to cool directly to space. Total
opacity in this spectral window between the 15 {$\mu$}m CO$_{2}$ band
and the CO$_{2}$ collision-induced absorption has a strong impact
on the temperature in the cloud convective layer. Improving our
knowledge of the gas opacities in these different windows through new
laboratory measurements or ab initio computations, as well as improving
the constraints on cloud opacities would help to separate gas and cloud
contributions and secure a better understanding of Venus's atmosphere
energy balance.
  doi = {10.1002/2015JE004794},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Encrenaz}, T. and {Greathouse}, T.~K. and {Lefèvre}, F. and 
	{Montmessin}, F. and {Forget}, F. and {Fouchet}, T. and {DeWitt}, C. and 
	{Richter}, M.~J. and {Lacy}, J.~H. and {Bézard}, B. and 
	{Atreya}, S.~K.},
  title = {{Seasonal variations of hydrogen peroxide and water vapor on Mars: Further indications of heterogeneous chemistry}},
  journal = {\aap},
  keywords = {planets and satellites: atmospheres, planets and satellites: terrestrial planets, planets and satellites: individual: Mars},
  year = 2015,
  volume = 578,
  eid = {A127},
  pages = {A127},
  abstract = {{We have completed our seasonal monitoring of hydrogen peroxide and water
vapor on Mars using ground-based thermal imaging spectroscopy, by
observing the planet in March 2014, when water vapor is maximum, and
July 2014, when, according to photochemical models, hydrogen peroxide is
expected to be maximum. Data have been obtained with the Texas Echelon
Cross Echelle Spectrograph (TEXES) mounted at the 3 m-Infrared Telescope
Facility (IRTF) at Maunakea Observatory. Maps of HDO and
H$_{2}$O$_{2}$ have been obtained using line depth ratios of
weak transitions of HDO and H$_{2}$O$_{2}$ divided by
CO$_{2}$. The retrieved maps of H$_{2}$O$_{2}$ are in
good agreement with predictions including a chemical transport model,
for both the March data (maximum water vapor) and the July data (maximum
hydrogen peroxide). The retrieved maps of HDO are compared with
simulations by Montmessin et al. (2005, J. Geophys. Res., 110, 03006)
and H$_{2}$O maps are inferred assuming a mean martian D/H ratio
of 5 times the terrestrial value. For regions of maximum values of
H$_{2}$O and H$_{2}$O$_{2}$, we derive, for March 1
2014 (Ls = 96{\deg}), H$_{2}$O$_{2}$ = 20+/-7 ppbv, HDO = 450
+/-75 ppbv (45 +/-8 pr-nm), and for July 3, 2014 (Ls = 156{\deg}),
H$_{2}$O$_{2}$ = 30+/-7 ppbv, HDO = 375+/-70 ppbv (22+/-3
pr-nm). In addition, the new observations are compared with LMD global
climate model results and we favor simulations of
H$_{2}$O$_{2}$ including heterogeneous reactions on
water-ice clouds.
  doi = {10.1051/0004-6361/201425448},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Charnay}, B. and {Barth}, E. and {Rafkin}, S. and {Narteau}, C. and 
	{Lebonnois}, S. and {Rodriguez}, S. and {Courrech Du Pont}, S. and 
	{Lucas}, A.},
  title = {{Methane storms as a driver of Titan's dune orientation}},
  journal = {Nature Geoscience},
  archiveprefix = {arXiv},
  eprint = {1504.03404},
  primaryclass = {astro-ph.EP},
  year = 2015,
  volume = 8,
  pages = {362-366},
  abstract = {{The equatorial regions of Saturn's moon Titan are covered by linear
dunes that propagate eastwards. Global climate models (GCMs), however,
predict westward mean surface winds at low latitudes on Titan, similar
to the trade winds on Earth. This apparent contradiction has been
attributed to Saturn's gravitational tides, large-scale topography and
wind statistics, but none of these hypotheses fully explains the global
eastward propagation of dunes in Titan's equatorial band. However, above
altitudes of about 5 km, Titan's atmosphere is in eastward
super-rotation, suggesting that this momentum may be delivered to the
surface. Here we assess the influence of equatorial tropical methane
storms--which develop at high altitudes during the equinox--on Titan's
dune orientation, using mesoscale simulations of convective methane
clouds with a GCM wind profile that includes super-rotation. We find
that these storms produce fast eastward gust fronts above the surface
that exceed the normal westward surface winds. These episodic gusts
generated by tropical storms are expected to dominate aeolian transport,
leading to eastward propagation of dunes. We therefore suggest a
coupling between super-rotation, tropical methane storms and dune
formation on Titan. This framework, applied to GCM predictions and
analogies to some terrestrial dune fields, explains the linear shape,
eastward propagation and poleward divergence of Titan's dunes, and
implies an equatorial origin of dune sand.
  doi = {10.1038/ngeo2406},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Medvedev}, A.~S. and {Gonz{\'a}lez-Galindo}, F. and {Yi{\v g}it}, E. and 
	{Feofilov}, A.~G. and {Forget}, F. and {Hartogh}, P.},
  title = {{Cooling of the Martian thermosphere by CO$_{2}$ radiation and gravity waves: An intercomparison study with two general circulation models}},
  journal = {Journal of Geophysical Research (Planets)},
  archiveprefix = {arXiv},
  eprint = {1504.05550},
  primaryclass = {astro-ph.EP},
  keywords = {Mars thermosphere, general circulation, CO$_{2}$cooling, gravity waves},
  year = 2015,
  volume = 120,
  pages = {913-927},
  abstract = {{Observations show that the lower thermosphere of Mars ({\tilde}100-140
km) is up to 40 K colder than the current general circulation models
(GCMs) can reproduce. Possible candidates for physical processes missing
in the models are larger abundances of atomic oxygen facilitating
stronger CO$_{2}$ radiative cooling and thermal effects of gravity
waves. Using two state-of-the-art Martian GCMs, the Laboratoire de
Météorologie Dynamique and Max Planck Institute models
that self-consistently cover the atmosphere from the surface to the
thermosphere, these physical mechanisms are investigated. Simulations
demonstrate that the CO$_{2}$ radiative cooling with a
sufficiently large atomic oxygen abundance and the gravity wave-induced
cooling can alone result in up to 40 K colder temperature in the lower
thermosphere. Accounting for both mechanisms produce stronger cooling at
high latitudes. However, radiative cooling effects peak above the
mesopause, while gravity wave cooling rates continuously increase with
height. Although both mechanisms act simultaneously, these peculiarities
could help to further quantify their relative contributions from future
  doi = {10.1002/2015JE004802},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Mulholland}, D.~P. and {Spiga}, A. and {Listowski}, C. and 
	{Read}, P.~L.},
  title = {{An assessment of the impact of local processes on dust lifting in martian climate models}},
  journal = {\icarus},
  keywords = {Aeolian processes, Mars, atmosphere, surface, Terrestrial planets},
  year = 2015,
  volume = 252,
  pages = {212-227},
  abstract = {{Simulation of the lifting of dust from the planetary surface is of
substantially greater importance on Mars than on Earth, due to the
fundamental role that atmospheric dust plays in the former's climate,
yet the dust emission parameterisations used to date in martian global
climate models (MGCMs) lag, understandably, behind their terrestrial
counterparts in terms of sophistication. Recent developments in
estimating surface roughness length over all martian terrains and in
modelling atmospheric circulations at regional to local scales (less
than O(100 km)) presents an opportunity to formulate an improved wind
stress lifting parameterisation. We have upgraded the conventional
scheme by including the spatially varying roughness length in the
lifting parameterisation in a fully consistent manner (thereby
correcting a possible underestimation of the true threshold level for
wind stress lifting), and used a modification to account for deviations
from neutral stability in the surface layer. Following these
improvements, it is found that wind speeds at typical MGCM resolution
never reach the lifting threshold at most gridpoints: winds fall
particularly short in the southern midlatitudes, where mean roughness is
large. Sub-grid scale variability, manifested in both the near-surface
wind field and the surface roughness, is then considered, and is found
to be a crucial means of bridging the gap between model winds and
thresholds. Both forms of small-scale variability contribute to the
formation of dust emission 'hotspots': areas within the model gridbox
with particularly favourable conditions for lifting, namely a smooth
surface combined with strong near-surface gusts. Such small-scale
emission could in fact be particularly influential on Mars, due both to
the intense positive radiative feedbacks that can drive storm growth and
a strong hysteresis effect on saltation. By modelling this variability,
dust lifting is predicted at the locations at which dust storms are
frequently observed, including the flushing storm sources of Chryse and
Utopia, and southern midlatitude areas from which larger storms tend to
initiate, such as Hellas and Solis Planum. The seasonal cycle of
emission, which includes a double-peaked structure in northern autumn
and winter, also appears realistic. Significant increases to lifting
rates are produced for any sensible choices of parameters controlling
the sub-grid distributions used, but results are sensitive to the
smallest scale of variability considered, which high-resolution
modelling suggests should be O(1 km) or less. Use of such models in
future will permit the use of a diagnosed (rather than prescribed)
variable gustiness intensity, which should further enhance dust lifting
in the southern hemisphere in particular.
  doi = {10.1016/j.icarus.2015.01.017},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Montabone}, L. and {Forget}, F. and {Millour}, E. and {Wilson}, R.~J. and 
	{Lewis}, S.~R. and {Cantor}, B. and {Kass}, D. and {Kleinb{\"o}hl}, A. and 
	{Lemmon}, M.~T. and {Smith}, M.~D. and {Wolff}, M.~J.},
  title = {{Eight-year climatology of dust optical depth on Mars}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1409.4841},
  primaryclass = {astro-ph.EP},
  keywords = {Mars, atmosphere, climate, Data reduction techniques},
  year = 2015,
  volume = 251,
  pages = {65-95},
  abstract = {{We have produced a multiannual climatology of airborne dust from martian
year 24-31 using multiple datasets of retrieved or estimated column
optical depths. The datasets are based on observations of the martian
atmosphere from April 1999 to July 2013 made by different orbiting
instruments: the Thermal Emission Spectrometer (TES) aboard Mars Global
Surveyor, the Thermal Emission Imaging System (THEMIS) aboard Mars
Odyssey, and the Mars Climate Sounder (MCS) aboard Mars Reconnaissance
Orbiter (MRO). The procedure we have adopted consists of gridding the
available retrievals of column dust optical depth (CDOD) from TES and
THEMIS nadir observations, as well as the estimates of this quantity
from MCS limb observations. Our gridding method calculates averages and
uncertainties on a regularly spaced spatio-temporal grid, using an
iterative procedure that is weighted in space, time, and retrieval
quality. The lack of observations at certain times and locations
introduces missing grid points in the maps, which therefore may result
in irregularly gridded (i.e. incomplete) fields. In order to evaluate
the strengths and weaknesses of the resulting gridded maps, we compare
with independent observations of CDOD by PanCam cameras and Mini-TES
spectrometers aboard the Mars Exploration Rovers ``Spirit'' and
``Opportunity'', by the Surface Stereo Imager aboard the Phoenix lander,
and by the Compact Reconnaissance Imaging Spectrometer for Mars aboard
MRO. We have statistically analyzed the irregularly gridded maps to
provide an overview of the dust climatology on Mars over eight years,
specifically in relation to its interseasonal and interannual
variability, in addition to provide a basis for instrument
intercomparison. Finally, we have produced regularly gridded maps of
CDOD by spatially interpolating the irregularly gridded maps using a
kriging method. These complete maps are used as dust scenarios in the
Mars Climate Database (MCD) version 5, and are useful in many modeling
applications. The two datasets for the eight available martian years are
publicly available and distributed with open access on the MCD website.
  doi = {10.1016/j.icarus.2014.12.034},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Vinatier}, S. and {Bézard}, B. and {Lebonnois}, S. and 
	{Teanby}, N.~A. and {Achterberg}, R.~K. and {Gorius}, N. and 
	{Mamoutkine}, A. and {Guandique}, E. and {Jolly}, A. and {Jennings}, D.~E. and 
	{Flasar}, F.~M.},
  title = {{Seasonal variations in Titan's middle atmosphere during the northern spring derived from Cassini/CIRS observations}},
  journal = {\icarus},
  keywords = {Titan, atmosphere, Infrared observations, Atmospheres, structure, Atmospheres, composition},
  year = 2015,
  volume = 250,
  pages = {95-115},
  abstract = {{We analyzed spectra acquired at the limb of Titan in the 2006-2013
period by the Cassini/Composite Infrared Spectrometer (CIRS) in order to
monitor the seasonal evolution of the thermal, gas composition and
aerosol spatial distributions. We are primarily interested here in the
seasonal changes after the northern spring equinox and interpret our
results in term of global circulation seasonal changes. Data cover the
600-1500 cm$^{-1}$ spectral range at a resolution of 0.5 or 15.5
cm$^{-1}$ and probe the 150-500 km vertical range with a vertical
resolution of about 30 km. Retrievals of the limb spectra acquired at
15.5 cm$^{-1}$ resolution allowed us to derive eight global maps
of temperature, aerosols and C$_{2}$H$_{2}$,
C$_{2}$H$_{6}$ and HCN molecular mixing ratios between July
2009 and May 2013. In order to have a better understanding of the global
changes taking place after the northern spring equinox, we analyzed 0.5
cm$^{-1}$ resolution limb spectra to infer the mixing ratio
profiles of 10 molecules for some latitudes. These profiles are compared
with CIRS observations performed during the northern winter. Our
observations are compatible with the coexistence of two circulation
cells upwelling at mid-latitudes and downwelling at both poles from at
last January 2010 to at least June 2010. One year later, in June 2011,
there are indications that the global circulation had reversed compared
to the winter situation, with a single pole-to-pole cell upwelling at
the north pole and downwelling at the south pole. Our observations show
that in December 2011, this new pole-to-pole cell has settled with a
downward velocity of 4.4 mm/s at 450 km above the south pole. Therefore,
in about two years after the equinox, the global circulation observed
during the northern winter has totally reversed, which is in agreement
with the predictions of general circulation models. We observe a sudden
unexpected temperature decrease above the south pole in February 2012,
which is probably related to the strong enhancement of molecular gas in
this region, acting as radiative coolers. In July and November 2012, we
observe a detached haze layer located around 320-330 km, which is
comparable to the altitude of the detached haze layer observed by the
Cassini Imaging Science Subsystem (ISS) in the UV.
  doi = {10.1016/j.icarus.2014.11.019},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lellouch}, E. and {de Bergh}, C. and {Sicardy}, B. and {Forget}, F. and 
	{Vangvichith}, M. and {K{\"a}ufl}, H.-U.},
  title = {{Exploring the spatial, temporal, and vertical distribution of methane in Pluto's atmosphere}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1403.3208},
  primaryclass = {astro-ph.EP},
  keywords = {Pluto, atmosphere, Infrared observations, Spectroscopy},
  year = 2015,
  volume = 246,
  pages = {268-278},
  abstract = {{High-resolution spectra of Pluto in the 1.66 {$\mu$}m region, recorded with
the VLT/CRIRES instrument in 2008 (2 spectra) and 2012 (5 spectra), are
analyzed to constrain the spatial and vertical distribution of methane
in Pluto's atmosphere and to search for mid-term (4 year) variability. A
sensitivity study to model assumptions (temperature structure, surface
pressure, Pluto's radius) is performed. Results indicate that (i) no
variation of the CH$_{4}$ atmospheric content (column-density or
mixing ratio) with Pluto rotational phase is present in excess of 20\%,
(ii) CH$_{4}$ column densities show at most marginal variations
between 2008 and 2012, with a best guess estimate of a {\sim}20\% decrease
over this time frame. As stellar occultations indicate that Pluto's
surface pressure has continued to increase over this period, this
implies a concomitant decrease of the methane mixing ratio (iii) the
data do not show evidence for an altitude-varying methane distribution;
in particular, they imply a roughly uniform mixing ratio in at least the
first 22-27 km of the atmosphere, and high concentrations of
low-temperature methane near the surface can be ruled out. Our results
are also best consistent with a relatively large ($\gt$1180 km) Pluto
radius. Comparison with predictions from a recently developed global
climate model indicates that these features are best explained if the
source of methane occurs in regional-scale CH$_{4}$ ice deposits,
including both low latitudes and high Northern latitudes, evidence for
which is present from the rotational and secular evolution of the
near-IR features due to CH$_{4}$ ice. Our ``best guess'' predictions
for the New Horizons encounter in 2015 are: a 1184 km radius, a 17
{$\mu$}bar surface pressure, and a 0.44\% CH$_{4}$ mixing ratio with
negligible longitudinal variations.
  doi = {10.1016/j.icarus.2014.03.027},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Chaufray}, J.-Y. and {Gonzalez-Galindo}, F. and {Forget}, F. and 
	{Lopez-Valverde}, M.~A. and {Leblanc}, F. and {Modolo}, R. and 
	{Hess}, S.},
  title = {{Variability of the hydrogen in the martian upper atmosphere as simulated by a 3D atmosphere-exosphere coupling}},
  journal = {\icarus},
  keywords = {Mars, atmosphere},
  year = 2015,
  volume = 245,
  pages = {282-294},
  abstract = {{We present the temporal variability of the atomic and molecular hydrogen
density derived from a 3D General Circulation Model describing the
martian atmosphere from the surface to the exobase. A kinetic exospheric
model is used to compute the hydrogen density above the exobase. We use
these models to study the diurnal and seasonal variations of the
hydrogen density and the Jeans escape rate as well as their variations
with solar activity, assuming a classic dust scenario. We find that the
diurnal variations of the hydrogen density are important with a peak in
the dawn region during equinoxes and a peak on the nightside during
solstices. These features result from the dynamics of the martian upper
atmosphere. The variations of the atomic hydrogen Jeans escape with
seasons and solar activity are in the range 1.3 {\times} 10$^{25}$
s$^{-1}$-4.4 {\times} 10$^{26}$ s$^{-1}$. A factor
{\sim}8 is due to the seasonal variations with a maximum during the
winter solstice in the northern hemisphere and a minimum during the
summer solstice in the northern hemisphere that we attribute to the
variation of the Mars-Sun distance. A factor {\sim}5 is due to the solar
cycle with a maximum escape rate at high solar activity. The variations
of the molecular hydrogen Jeans escape with seasons and solar activity
are in the range 3 {\times} 10$^{22}$ s$^{-1}$-6 {\times}
10$^{24}$ s$^{-1}$. A factor {\sim}10 is due to the seasonal
variations with a maximum during the winter solstice in the northern
hemisphere and a minimum during the summer solstice in the northern
hemisphere. A factor {\sim}20 is due to the solar cycle with a maximum
escape rate at high solar activity. If Jeans escape is the major escape
channel for hydrogen, the hydrogen escape is never limited by diffusion.
The hydrogen density above 10,000 km presents seasonal and solar cycle
variations similar to the Jeans escape rate at all latitudes and local
times. This 3D temporal model of the hydrogen thermosphere/exosphere
will be useful to interpret future MAVEN observations and the
consequences of the hydrogen corona variability on the martian plasma
  doi = {10.1016/j.icarus.2014.08.038},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Alexe}, M. and {Bergamaschi}, P. and {Segers}, A. and {Detmers}, R. and 
	{Butz}, A. and {Hasekamp}, O. and {Guerlet}, S. and {Parker}, R. and 
	{Boesch}, H. and {Frankenberg}, C. and {Scheepmaker}, R.~A. and 
	{Dlugokencky}, E. and {Sweeney}, C. and {Wofsy}, S.~C. and {Kort}, E.~A.
  title = {{Inverse modelling of CH$_{4}$ emissions for 2010-2011 using different satellite retrieval products from GOSAT and SCIAMACHY}},
  journal = {Atmospheric Chemistry \& Physics},
  year = 2015,
  volume = 15,
  pages = {113-133},
  abstract = {{At the beginning of 2009 new space-borne observations of dry-air
column-averaged mole fractions of atmospheric methane (XCH$_{4}$)
became available from the Thermal And Near infrared Sensor for carbon
Observations-Fourier Transform Spectrometer (TANSO-FTS) instrument on
board the Greenhouse Gases Observing SATellite (GOSAT). Until April 2012
concurrent $\{$methane (CH$_{4}$) retrievals$\}$ were provided by the
SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY
(SCIAMACHY) instrument on board the ENVironmental SATellite (ENVISAT).
The GOSAT and SCIAMACHY XCH$_{4}$ retrievals can be compared
emissions between January 2010 and December 2011, using the TM5-4DVAR
inverse modelling system. In addition to satellite data, high-accuracy
measurements from the Cooperative Air Sampling Network of the National
Oceanic and Atmospheric Administration Earth System Research Laboratory
(NOAA ESRL) are used, providing strong constraints on the remote surface
atmosphere. We discuss five inversion scenarios that make use of
different GOSAT and SCIAMACHY XCH$_{4}$ retrieval products,
including two sets of GOSAT proxy retrievals processed independently by
the Netherlands Institute for Space Research (SRON)/Karlsruhe Institute
of Technology (KIT), and the University of Leicester (UL), and the
RemoTeC ``Full-Physics'' (FP) XCH$_{4}$ retrievals available from
SRON/KIT. The GOSAT-based inversions show significant reductions in the
root mean square (rms) difference between retrieved and modelled
XCH$_{4}$, and require much smaller bias corrections compared to
the inversion using SCIAMACHY retrievals, reflecting the higher
precision and relative accuracy of the GOSAT XCH$_{4}$. Despite
the large differences between the GOSAT and SCIAMACHY retrievals, 2-year
average emission maps show overall good agreement among all
satellite-based inversions, with consistent flux adjustment patterns,
particularly across equatorial Africa and North America. Over North
America, the satellite inversions result in a significant redistribution
of CH$_{4}$ emissions from North-East to South-Central United
States. This result is consistent with recent independent studies
suggesting a systematic underestimation of CH$_{4}$ emissions from
North American fossil fuel sources in bottom-up inventories, likely
related to natural gas production facilities. Furthermore, all four
satellite inversions yield lower CH$_{4}$ fluxes across the Congo
basin compared to the NOAA-only scenario, but higher emissions across
tropical East Africa. The GOSAT and SCIAMACHY inversions show similar
performance when validated against independent shipboard and aircraft
observations, and XCH$_{4}$ retrievals available from the Total
Carbon Column Observing Network (TCCON).
  doi = {10.5194/acp-15-113-2015},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}