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@comment{{Command line: /usr/bin/bib2bib --quiet -c 'not journal:"Discussions"' -c year=2018 -c $type="ARTICLE" -oc pub2018.txt -ob pub2018.bib}}
  author = {{Wordsworth}, R. and {Ehlmann}, B. and {Forget}, F. and {Haberle}, R. and 
	{Head}, J. and {Kerber}, L.},
  title = {{Healthy debate on early Mars}},
  journal = {Nature Geoscience},
  year = 2018,
  volume = 11,
  pages = {888-888},
  doi = {10.1038/s41561-018-0267-5},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{S{\'a}nchez-Lavega}, A. and {Garro}, A. and {del R{\'{\i}}o-Gaztelurrutia}, T. and 
	{Hueso}, R. and {Ordo{\~n}ez-Etxeberria}, I. and {Chen Chen}, H. and 
	{Cardes{\'{\i}}n-Moinelo}, A. and {Titov}, D. and {Wood}, S. and 
	{Almeida}, M. and {Spiga}, A. and {Forget}, F. and {M{\"a}{\"a}tt{\"a}nen}, A. and 
	{Hoffmann}, H. and {Gondet}, B.},
  title = {{A Seasonally Recurrent Annular Cyclone in Mars Northern Latitudes and Observations of a Companion Vortex}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars atmosphere, atmospheric dynamics},
  year = 2018,
  volume = 123,
  pages = {3020-3034},
  abstract = {{We study a seasonally recurrent cyclone and related cloud phenomena
observed on Mars at L$_{s}$  120{\deg}, latitude  60{\deg}N, and
longitude 90{\deg}W from images obtained with cameras in different
spacecraft between 1995 and 2018. A remarkable double cyclone formed in
2012 and we present a detailed study of its dynamics using images from
Mars Express and Mars Reconnaissance Orbiter obtained between 6 June and
9 July. A double cyclone was also observed in 2006 and 2008. In other
Martian years the primary cyclone showed an annular cloud morphology
with a large water ice cloud observed eastward of it. The cyclones have
a size of  600-800 km with a cloud-free core of a radius  100-300 km.
Tangential velocities measured from cloud tracking in 2012 images are
5-20 m/s$^{-1}$ at 10-km altitude and double cyclone moved
eastward with a velocity of 4 m/s$^{-1}$ during its lifetime of
increasing insolation as the sol progresses, a part of the clouds
evaporate, the winds weaken, and the vortices lose coherence. This
phenomenon forms under high-temperature gradients in a region with a
large north-south topographic slope and has been recurrent each Martian
year between 1995 and 2018. We argue the interest of studying its
changing properties each Martian year in order to explore their possible
relationship to the state of the Martian atmosphere at L$_{s}$
  doi = {10.1029/2018JE005740},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Grundy}, W.~M. and {Bertrand}, T. and {Binzel}, R.~P. and {Buie}, M.~W. and 
	{Buratti}, B.~J. and {Cheng}, A.~F. and {Cook}, J.~C. and {Cruikshank}, D.~P. and 
	{Devins}, S.~L. and {Dalle Ore}, C.~M. and {Earle}, A.~M. and 
	{Ennico}, K. and {Forget}, F. and {Gao}, P. and {Gladstone}, G.~R. and 
	{Howett}, C.~J.~A. and {Jennings}, D.~E. and {Kammer}, J.~A. and 
	{Lauer}, T.~R. and {Linscott}, I.~R. and {Lisse}, C.~M. and 
	{Lunsford}, A.~W. and {McKinnon}, W.~B. and {Olkin}, C.~B. and 
	{Parker}, A.~H. and {Protopapa}, S. and {Quirico}, E. and {Reuter}, D.~C. and 
	{Schmitt}, B. and {Singer}, K.~N. and {Spencer}, J.~A. and {Stern}, S.~A. and 
	{Strobel}, D.~F. and {Summers}, M.~E. and {Weaver}, H.~A. and 
	{Weigle}, G.~E. and {Wong}, M.~L. and {Young}, E.~F. and {Young}, L.~A. and 
	{Zhang}, X.},
  title = {{Pluto's haze as a surface material}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1903.03728},
  primaryclass = {astro-ph.EP},
  keywords = {Pluto, surface, atmosphere, Geological processes, Ices, Photochemistry},
  year = 2018,
  volume = 314,
  pages = {232-245},
  abstract = {{Pluto's atmospheric haze settles out rapidly compared with geological
timescales. It needs to be accounted for as a surface material, distinct
from Pluto's icy bedrock and from the volatile ices that migrate via
sublimation and condensation on seasonal timescales. This paper explores
how a steady supply of atmospheric haze might affect three distinct
provinces on Pluto. We pose the question of why they each look so
different from one another if the same haze material is settling out
onto all of them. Cthulhu is a more ancient region with comparatively
little present-day geological activity, where the haze appears to simply
accumulate over time. Sputnik Planitia is a very active region where
glacial convection, as well as sublimation and condensation rapidly
refresh the surface, hiding recently deposited haze from view. Lowell
Regio is a region of intermediate age featuring very distinct coloration
from the rest of Pluto. Using a simple model haze particle as a
colorant, we are not able to match the colors in both Lowell Regio and
Cthulhu. To account for their distinct colors, we propose that after
arrival at Pluto's surface, haze particles may be less inert than might
be supposed from the low surface temperatures. They must either interact
with local materials and environments to produce distinct products in
different regions, or else the supply of haze must be non-uniform in
time and/or location, such that different products are delivered to
different places.
  doi = {10.1016/j.icarus.2018.05.019},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lebonnois}, S. and {Schubert}, G. and {Forget}, F. and {Spiga}, A.
  title = {{Planetary boundary layer and slope winds on Venus}},
  journal = {\icarus},
  keywords = {Venus, Atmosphere, Planetary boundary layer, Slope winds},
  year = 2018,
  volume = 314,
  pages = {149-158},
  abstract = {{Few constraints are available to characterize the deep atmosphere of
Venus, though this region is crucial to understand the interactions
between surface and atmosphere on Venus. Based on simulations performed
with the IPSL Venus Global Climate Model, the possible structure and
characteristics of Venus' planetary boundary layer (PBL) are
investigated. The vertical profile of the potential temperature in the
deepest 10 km above the surface and its diurnal variations are
controlled by radiative and dynamical processes. The model predicts a
diurnal cycle for the PBL activity, with a stable nocturnal PBL while
convective activity develops during daytime. The diurnal convective PBL
is strongly correlated with surface solar flux and is maximum around
noon and in low latitude regions. It typically reaches less than 2 km
above the surface, but its vertical extension is much higher over high
elevations, and more precisely over the western flanks of elevated
terrains. This correlation is explained by the impact of surface winds,
which undergo a diurnal cycle with downward katabatic winds at night and
upward anabatic winds during the day along the slopes of high-elevation
terrains. The convergence of these daytime anabatic winds induces upward
vertical winds, that are responsible for the correlation between height
of the convective boundary layer and topography.
  doi = {10.1016/j.icarus.2018.06.006},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Garate-Lopez}, I. and {Lebonnois}, S.},
  title = {{Latitudinal variation of clouds' structure responsible for Venus' cold collar}},
  journal = {\icarus},
  keywords = {Venus atmosphere, Cold collar, Modelling},
  year = 2018,
  volume = 314,
  pages = {1-11},
  abstract = {{Global Climate Models (GCM) are very useful tools to study theoretically
the general dynamics and specific phenomena in planetary atmospheres. In
the case of Venus, several GCMs succeeded in reproducing the
atmosphere's superrotation and the global temperature field. However,
the highly variable polar temperature and the permanent cold collar
present at 60$^{o}$ -80$^{o}$ latitude have not been
reproduced satisfactorily yet.

Here we improve the radiative transfer scheme of the Institut Pierre
Simon Laplace Venus GCM in order to numerically simulate the polar
thermal features in Venus atmosphere. The main difference with the
previous model is that we now take into account the latitudinal
variation of the cloud structure. Both solar heating rates and infrared
cooling rates have been modified to consider the cloud top's altitude
decrease toward the poles and the variation in latitude of the different
particle modes' abundances.

A new structure that closely resembles the observed cold collar appears
in the average temperature field at 2 {\times}10$^{4}$ - 4
{\times}10$^{3}$  Pa ({\sim} 62 - 66  km) altitude range and
60$^{o}$ -90$^{o}$ latitude band. It is not isolated
from the pole as in the observation-based maps, but the obtained
temperature values (220 K) are in good agreement with observed values.
Temperature polar maps across this region show an inner warm region
where the polar vortex is observed, but the obtained 230 K average value
is colder than the observed mean value and the simulated horizontal
structure does not show the fine-scale features present within the

The comparison with a simulation that does not take into account the
latitudinal variation of the cloud structure in the infrared cooling
computation, shows that the cloud structure is essential in the cold
collar formation. Although our analysis focuses on the improvement of
the radiative forcing and the variations it causes in the thermal
structure, polar dynamics is definitely affected by this modified
environment and a noteworthy upwelling motion is found in the cold
collar area.
  doi = {10.1016/j.icarus.2018.05.011},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Tinetti}, G. and {Drossart}, P. and {Eccleston}, P. and {Hartogh}, P. and 
	{Heske}, A. and {Leconte}, J. and {Micela}, G. and {Ollivier}, M. and 
	{Pilbratt}, G. and {Puig}, L. and {Turrini}, D. and {Vandenbussche}, B. and 
	{Wolkenberg}, P. and {Beaulieu}, J.-P. and {Buchave}, L.~A. and 
	{Ferus}, M. and {Griffin}, M. and {Guedel}, M. and {Justtanont}, K. and 
	{Lagage}, P.-O. and {Machado}, P. and {Malaguti}, G. and {Min}, M. and 
	{N{\o}rgaard-Nielsen}, H.~U. and {Rataj}, M. and {Ray}, T. and 
	{Ribas}, I. and {Swain}, M. and {Szabo}, R. and {Werner}, S. and 
	{Barstow}, J. and {Burleigh}, M. and {Cho}, J. and {du Foresto}, V.~C. and 
	{Coustenis}, A. and {Decin}, L. and {Encrenaz}, T. and {Galand}, M. and 
	{Gillon}, M. and {Helled}, R. and {Morales}, J.~C. and {Mu{\~n}oz}, A.~G. and 
	{Moneti}, A. and {Pagano}, I. and {Pascale}, E. and {Piccioni}, G. and 
	{Pinfield}, D. and {Sarkar}, S. and {Selsis}, F. and {Tennyson}, J. and 
	{Triaud}, A. and {Venot}, O. and {Waldmann}, I. and {Waltham}, D. and 
	{Wright}, G. and {Amiaux}, J. and {Auguères}, J.-L. and 
	{Berthé}, M. and {Bezawada}, N. and {Bishop}, G. and {Bowles}, N. and 
	{Coffey}, D. and {Colomé}, J. and {Crook}, M. and {Crouzet}, P.-E. and 
	{Da Peppo}, V. and {Sanz}, I.~E. and {Focardi}, M. and {Frericks}, M. and 
	{Hunt}, T. and {Kohley}, R. and {Middleton}, K. and {Morgante}, G. and 
	{Ottensamer}, R. and {Pace}, E. and {Pearson}, C. and {Stamper}, R. and 
	{Symonds}, K. and {Rengel}, M. and {Renotte}, E. and {Ade}, P. and 
	{Affer}, L. and {Alard}, C. and {Allard}, N. and {Altieri}, F. and 
	{André}, Y. and {Arena}, C. and {Argyriou}, I. and {Aylward}, A. and 
	{Baccani}, C. and {Bakos}, G. and {Banaszkiewicz}, M. and {Barlow}, M. and 
	{Batista}, V. and {Bellucci}, G. and {Benatti}, S. and {Bernardi}, P. and 
	{Bézard}, B. and {Blecka}, M. and {Bolmont}, E. and {Bonfond}, B. and 
	{Bonito}, R. and {Bonomo}, A.~S. and {Brucato}, J.~R. and {Brun}, A.~S. and 
	{Bryson}, I. and {Bujwan}, W. and {Casewell}, S. and {Charnay}, B. and 
	{Pestellini}, C.~C. and {Chen}, G. and {Ciaravella}, A. and 
	{Claudi}, R. and {Clédassou}, R. and {Damasso}, M. and {Damiano}, M. and 
	{Danielski}, C. and {Deroo}, P. and {Di Giorgio}, A.~M. and 
	{Dominik}, C. and {Doublier}, V. and {Doyle}, S. and {Doyon}, R. and 
	{Drummond}, B. and {Duong}, B. and {Eales}, S. and {Edwards}, B. and 
	{Farina}, M. and {Flaccomio}, E. and {Fletcher}, L. and {Forget}, F. and 
	{Fossey}, S. and {Fr{\"a}nz}, M. and {Fujii}, Y. and {Garc{\'{\i}}a-Piquer}, {\'A}. and 
	{Gear}, W. and {Geoffray}, H. and {Gérard}, J.~C. and {Gesa}, L. and 
	{Gomez}, H. and {Graczyk}, R. and {Griffith}, C. and {Grodent}, D. and 
	{Guarcello}, M.~G. and {Gustin}, J. and {Hamano}, K. and {Hargrave}, P. and 
	{Hello}, Y. and {Heng}, K. and {Herrero}, E. and {Hornstrup}, A. and 
	{Hubert}, B. and {Ida}, S. and {Ikoma}, M. and {Iro}, N. and 
	{Irwin}, P. and {Jarchow}, C. and {Jaubert}, J. and {Jones}, H. and 
	{Julien}, Q. and {Kameda}, S. and {Kerschbaum}, F. and {Kervella}, P. and 
	{Koskinen}, T. and {Krijger}, M. and {Krupp}, N. and {Lafarga}, M. and 
	{Landini}, F. and {Lellouch}, E. and {Leto}, G. and {Luntzer}, A. and 
	{Rank-L{\"u}ftinger}, T. and {Maggio}, A. and {Maldonado}, J. and 
	{Maillard}, J.-P. and {Mall}, U. and {Marquette}, J.-B. and 
	{Mathis}, S. and {Maxted}, P. and {Matsuo}, T. and {Medvedev}, A. and 
	{Miguel}, Y. and {Minier}, V. and {Morello}, G. and {Mura}, A. and 
	{Narita}, N. and {Nascimbeni}, V. and {Nguyen Tong}, N. and 
	{Noce}, V. and {Oliva}, F. and {Palle}, E. and {Palmer}, P. and 
	{Pancrazzi}, M. and {Papageorgiou}, A. and {Parmentier}, V. and 
	{Perger}, M. and {Petralia}, A. and {Pezzuto}, S. and {Pierrehumbert}, R. and 
	{Pillitteri}, I. and {Piotto}, G. and {Pisano}, G. and {Prisinzano}, L. and 
	{Radioti}, A. and {Réess}, J.-M. and {Rezac}, L. and {Rocchetto}, M. and 
	{Rosich}, A. and {Sanna}, N. and {Santerne}, A. and {Savini}, G. and 
	{Scandariato}, G. and {Sicardy}, B. and {Sierra}, C. and {Sindoni}, G. and 
	{Skup}, K. and {Snellen}, I. and {Sobiecki}, M. and {Soret}, L. and 
	{Sozzetti}, A. and {Stiepen}, A. and {Strugarek}, A. and {Taylor}, J. and 
	{Taylor}, W. and {Terenzi}, L. and {Tessenyi}, M. and {Tsiaras}, A. and 
	{Tucker}, C. and {Valencia}, D. and {Vasisht}, G. and {Vazan}, A. and 
	{Vilardell}, F. and {Vinatier}, S. and {Viti}, S. and {Waters}, R. and 
	{Wawer}, P. and {Wawrzaszek}, A. and {Whitworth}, A. and {Yung}, Y.~L. and 
	{Yurchenko}, S.~N. and {Osorio}, M.~R.~Z. and {Zellem}, R. and 
	{Zingales}, T. and {Zwart}, F.},
  title = {{A chemical survey of exoplanets with ARIEL}},
  journal = {Experimental Astronomy},
  keywords = {Exoplanets, Space missions, IR spectroscopy, Molecular signatures},
  year = 2018,
  volume = 46,
  pages = {135-209},
  abstract = {{Thousands of exoplanets have now been discovered with a huge range of
masses, sizes and orbits: from rocky Earth-like planets to large gas
giants grazing the surface of their host star. However, the essential
nature of these exoplanets remains largely mysterious: there is no
known, discernible pattern linking the presence, size, or orbital
parameters of a planet to the nature of its parent star. We have little
idea whether the chemistry of a planet is linked to its formation
environment, or whether the type of host star drives the physics and
chemistry of the planet's birth, and evolution. ARIEL was conceived to
observe a large number ( 1000) of transiting planets for statistical
understanding, including gas giants, Neptunes, super-Earths and
Earth-size planets around a range of host star types using transit
spectroscopy in the 1.25-7.8 {$\mu$}m spectral range and multiple
narrow-band photometry in the optical. ARIEL will focus on warm and hot
planets to take advantage of their well-mixed atmospheres which should
show minimal condensation and sequestration of high-Z materials compared
to their colder Solar System siblings. Said warm and hot atmospheres are
expected to be more representative of the planetary bulk composition.
Observations of these warm/hot exoplanets, and in particular of their
elemental composition (especially C, O, N, S, Si), will allow the
understanding of the early stages of planetary and atmospheric formation
during the nebular phase and the following few million years. ARIEL will
thus provide a representative picture of the chemical nature of the
exoplanets and relate this directly to the type and chemical environment
of the host star. ARIEL is designed as a dedicated survey mission for
combined-light spectroscopy, capable of observing a large and
well-defined planet sample within its 4-year mission lifetime. Transit,
eclipse and phase-curve spectroscopy methods, whereby the signal from
the star and planet are differentiated using knowledge of the planetary
ephemerides, allow us to measure atmospheric signals from the planet at
levels of 10-100 part per million (ppm) relative to the star and, given
the bright nature of targets, also allows more sophisticated techniques,
such as eclipse mapping, to give a deeper insight into the nature of the
atmosphere. These types of observations require a stable payload and
satellite platform with broad, instantaneous wavelength coverage to
detect many molecular species, probe the thermal structure, identify
clouds and monitor the stellar activity. The wavelength range proposed
covers all the expected major atmospheric gases from e.g.
H$_{2}$O, CO$_{2}$, CH$_{4}$ NH$_{3}$, HCN,
H$_{2}$S through to the more exotic metallic compounds, such as
TiO, VO, and condensed species. Simulations of ARIEL performance in
conducting exoplanet surveys have been performed - using conservative
estimates of mission performance and a full model of all significant
noise sources in the measurement - using a list of potential ARIEL
targets that incorporates the latest available exoplanet statistics. The
conclusion at the end of the Phase A study, is that ARIEL - in line with
the stated mission objectives - will be able to observe about 1000
exoplanets depending on the details of the adopted survey strategy, thus
confirming the feasibility of the main science objectives.
  doi = {10.1007/s10686-018-9598-x},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Spiga}, A. and {Banfield}, D. and {Teanby}, N.~A. and {Forget}, F. and 
	{Lucas}, A. and {Kenda}, B. and {Rodriguez Manfredi}, J.~A. and 
	{Widmer-Schnidrig}, R. and {Murdoch}, N. and {Lemmon}, M.~T. and 
	{Garcia}, R.~F. and {Martire}, L. and {Karatekin}, {\"O}. and 
	{Le Maistre}, S. and {Van Hove}, B. and {Dehant}, V. and {Lognonné}, P. and 
	{Mueller}, N. and {Lorenz}, R. and {Mimoun}, D. and {Rodriguez}, S. and 
	{Beucler}, {\'E}. and {Daubar}, I. and {Golombek}, M.~P. and 
	{Bertrand}, T. and {Nishikawa}, Y. and {Millour}, E. and {Rolland}, L. and 
	{Brissaud}, Q. and {Kawamura}, T. and {Mocquet}, A. and {Martin}, R. and 
	{Clinton}, J. and {Stutzmann}, {\'E}. and {Spohn}, T. and {Smrekar}, S. and 
	{Banerdt}, W.~B.},
  title = {{Atmospheric Science with InSight}},
  journal = {\ssr},
  keywords = {Mars, InSight, Atmospheric science, Planetary atmospheres},
  year = 2018,
  volume = 214,
  eid = {109},
  pages = {109},
  abstract = {{In November 2018, for the first time a dedicated geophysical station,
the InSight lander, will be deployed on the surface of Mars. Along with
the two main geophysical packages, the Seismic Experiment for Interior
Structure (SEIS) and the Heat-Flow and Physical Properties Package
(HP$^{3}$), the InSight lander holds a highly sensitive pressure
sensor (PS) and the Temperature and Winds for InSight (TWINS)
instrument, both of which (along with the InSight FluxGate (IFG)
Magnetometer) form the Auxiliary Sensor Payload Suite (APSS). Associated
with the RADiometer (RAD) instrument which will measure the surface
brightness temperature, and the Instrument Deployment Camera (IDC) which
will be used to quantify atmospheric opacity, this will make InSight
capable to act as a meteorological station at the surface of Mars. While
probing the internal structure of Mars is the primary scientific goal of
the mission, atmospheric science remains a key science objective for
InSight. InSight has the potential to provide a more continuous and
higher-frequency record of pressure, air temperature and winds at the
surface of Mars than previous in situ missions. In the paper, key
results from multiscale meteorological modeling, from Global Climate
Models to Large-Eddy Simulations, are described as a reference for
future studies based on the InSight measurements during operations. We
summarize the capabilities of InSight for atmospheric observations, from
profiling during Entry, Descent and Landing to surface measurements
(pressure, temperature, winds, angular momentum), and the plans for how
InSight's sensors will be used during operations, as well as possible
synergies with orbital observations. In a dedicated section, we describe
the seismic impact of atmospheric phenomena (from the point of view of
both ``noise'' to be decorrelated from the seismic signal and ``signal'' to
provide information on atmospheric processes). We discuss in this
framework Planetary Boundary Layer turbulence, with a focus on
convective vortices and dust devils, gravity waves (with idealized
modeling), and large-scale circulations. Our paper also presents
possible new, exploratory, studies with the InSight instrumentation:
surface layer scaling and exploration of the Monin-Obukhov model,
aeolian surface changes and saltation / lifing studies, and monitoring
of secular pressure changes. The InSight mission will be instrumental in
broadening the knowledge of the Martian atmosphere, with a unique set of
measurements from the surface of Mars.
  doi = {10.1007/s11214-018-0543-0},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Read}, W.~G. and {Tamppari}, L.~K. and {Livesey}, N.~J. and 
	{Clancy}, R.~T. and {Forget}, F. and {Hartogh}, P. and {Rafkin}, S.~C.~R. and 
	{Chattopadhyay}, G.},
  title = {{Retrieval of wind, temperature, water vapor and other trace constituents in the Martian Atmosphere}},
  journal = {\planss},
  keywords = {Mars, Atmosphere, Wind, Isotopes, Temperature, Humidity, Composition},
  year = 2018,
  volume = 161,
  pages = {26-40},
  abstract = {{Atmospheric limb sounding is a well-established technique for measuring
atmospheric temperature, composition, and wind. The theoretical
capabilities of a submillimeter limb sounder placed in low Mars orbit
are quantified, with a particular focus on the ability to make profile
measurements of line-of-sight wind, temperature, water vapor, deuterated
water vapor, several isotopes of carbon monoxide, oxygen-18 carbon
dioxide, ozone, and hydrogen peroxide. We identify cases where all such
measurements can be made within a single 25-70 GHz wide region of the
submillimeter spectrum, enabling use of a single state-of-the-art
submillimeter receiver. Six potential spectral regions, approximately
centered at 335 GHz, 450 GHz, 550 GHz, 900 GHz, 1000 GHz, and 1130 GHz
are found, any one of which can provide a complete measurement suite.
The expected precision and vertical resolution of temperature,
composition, and wind measurements from instruments in each range are
quantified. This work thus follows on from that of Urban et al. (2005),
Kasai et al. (2012), and earlier studies, expanding them to consider
many alternative observing frequency regions. In general, performance
(in terms of measurement precision and vertical resolution) is improved
with increasing observation frequency. In part this is due to our choice
to assume the same antenna size for each frequency, thus providing a
narrower field of view for the higher frequency configurations. The
general increase in emission line strengths with increasing frequency
also contributes to this improved performance in some cases. However,
increased instrument power needs for the higher frequency configurations
may argue against their choice in some mission scenarios.
  doi = {10.1016/j.pss.2018.05.004},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Navarro}, T. and {Schubert}, G. and {Lebonnois}, S.},
  title = {{Author Correction: Atmospheric mountain wave generation on Venus and its influence on the solid planet's rotation rate}},
  journal = {Nature Geoscience},
  year = 2018,
  volume = 11,
  pages = {965-965},
  abstract = {{In the version of this Article originally published, a statement
regarding past measurements of the length of day and rotation rate of
Venus was potentially misleading. The original statement has now been
replaced in the online versions of this Article, to acknowledge that
neither Magellan nor Venus Express measured an instantaneous rotation
  doi = {10.1038/s41561-018-0257-7},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lefèvre}, M. and {Lebonnois}, S. and {Spiga}, A.},
  title = {{Three-Dimensional Turbulence-Resolving Modeling of the Venusian Cloud Layer and Induced Gravity Waves: Inclusion of Complete Radiative Transfer and Wind Shear}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Venus, modeling, convection, gravity waves},
  year = 2018,
  volume = 123,
  pages = {2773-2789},
  abstract = {{Venus' convective cloud layers and associated gravity waves strongly
impact the local and global budget of heat, momentum, and chemical
species. Here we use for the first time three-dimensional
turbulence-resolving dynamical integrations of Venus' atmosphere from
the surface to 100-km altitude, coupled with fully interactive radiative
transfer computations. We show that this enables to correctly reproduce
the vertical position (46- to 55-km altitude) and thickness (9 km) of
the main convective cloud layer measured by Venus Express and Akatsuki
radio occultations, as well as the intensity of convective plumes (3
m/s) measured by VEGA balloons. Both the radiative forcing in the
visible and the large-scale dynamical impact play a role in the
variability of the cloud convective activity with local time and
latitude. Our model reproduces the diurnal cycle in cloud convection
observed by Akatsuki at the low latitudes and the lack thereof observed
by Venus Express at the equator. The observed enhancement of cloud
convection at high latitudes is simulated by our model, although
underestimated compared to observations. We show that the influence of
the vertical shear of horizontal superrotating winds must be accounted
for in our model to allow for gravity waves of the observed intensity
($\gt$1 K) and horizontal wavelength (up to 20 km) to be generated
through the obstacle effect mechanism. The vertical extent of our model
also allows us to predict for the first time a 7-km-thick convective
layer at the cloud top (70-km altitude) caused by the solar absorption
of the unknown ultraviolet absorber.
  doi = {10.1029/2018JE005679},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Yung}, Y.~L. and {Chen}, P. and {Nealson}, K. and {Atreya}, S. and 
	{Beckett}, P. and {Blank}, J.~G. and {Ehlmann}, B. and {Eiler}, J. and 
	{Etiope}, G. and {Ferry}, J.~G. and {Forget}, F. and {Gao}, P. and 
	{Hu}, R. and {Kleinb{\"o}hl}, A. and {Klusman}, R. and {Lefèvre}, F. and 
	{Miller}, C. and {Mischna}, M. and {Mumma}, M. and {Newman}, S. and 
	{Oehler}, D. and {Okumura}, M. and {Oremland}, R. and {Orphan}, V. and 
	{Popa}, R. and {Russell}, M. and {Shen}, L. and {Sherwood Lollar}, B. and 
	{Staehle}, R. and {Stamenkovi{\'c}}, V. and {Stolper}, D. and 
	{Templeton}, A. and {Vandaele}, A.~C. and {Viscardy}, S. and 
	{Webster}, C.~R. and {Wennberg}, P.~O. and {Wong}, M.~L. and 
	{Worden}, J.},
  title = {{Methane on Mars and Habitability: Challenges and Responses}},
  journal = {Astrobiology},
  year = 2018,
  volume = 18,
  pages = {1221-1242},
  abstract = {{Recent measurements of methane (CH$_{4}$) by the Mars Science
Laboratory (MSL) now confront us with robust data that demand
interpretation. Thus far, the MSL data have revealed a baseline level of
CH$_{4}$ ({\tilde}0.4 parts per billion by volume [ppbv]), with
seasonal variations, as well as greatly enhanced spikes of
CH$_{4}$ with peak abundances of {\tilde}7 ppbv. What do these
CH$_{4}$ revelations with drastically different abundances and
temporal signatures represent in terms of interior geochemical
processes, or is martian CH$_{4}$ a biosignature? Discerning how
CH$_{4}$ generation occurs on Mars may shed light on the potential
habitability of Mars. There is no evidence of life on the surface of
Mars today, but microbes might reside beneath the surface. In this case,
the carbon flux represented by CH$_{4}$ would serve as a link
between a putative subterranean biosphere on Mars and what we can
measure above the surface. Alternatively, CH$_{4}$ records modern
geochemical activity. Here we ask the fundamental question: how active
is Mars, geochemically and/or biologically? In this article, we examine
geological, geochemical, and biogeochemical processes related to our
overarching question. The martian atmosphere and surface are an
overwhelmingly oxidizing environment, and life requires pairing of
electron donors and electron acceptors, that is, redox gradients, as an
essential source of energy. Therefore, a fundamental and critical
question regarding the possibility of life on Mars is, ``Where can we
find redox gradients as energy sources for life on Mars?'' Hence,
regardless of the pathway that generates CH$_{4}$ on Mars, the
presence of CH$_{4}$, a reduced species in an oxidant-rich
environment, suggests the possibility of redox gradients supporting life
and habitability on Mars. Recent missions such as ExoMars Trace Gas
Orbiter may provide mapping of the global distribution of
CH$_{4}$. To discriminate between abiotic and biotic sources of
CH$_{4}$ on Mars, future studies should use a series of diagnostic
geochemical analyses, preferably performed below the ground or at the
ground/atmosphere interface, including measurements of CH$_{4}$
isotopes, methane/ethane ratios, H$_{2}$ gas concentration, and
species such as acetic acid. Advances in the fields of Mars exploration
and instrumentation will be driven, augmented, and supported by an
improved understanding of atmospheric chemistry and dynamics, deep
subsurface biogeochemistry, astrobiology, planetary geology, and
geophysics. Future Mars exploration programs will have to expand the
integration of complementary areas of expertise to generate synergistic
and innovative ideas to realize breakthroughs in advancing our
understanding of the potential of life and habitable conditions having
existed on Mars. In this spirit, we conducted a set of interdisciplinary
workshops. From this series has emerged a vision of technological,
theoretical, and methodological innovations to explore the martian
subsurface and to enhance spatial tracking of key volatiles, such as
  doi = {10.1089/ast.2018.1917},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Esposito}, F. and {Debei}, S. and {Bettanini}, C. and {Molfese}, C. and 
	{Arruego Rodr{\'{\i}}guez}, I. and {Colombatti}, G. and {Harri}, A.-M. and 
	{Montmessin}, F. and {Wilson}, C. and {Aboudan}, A. and {Schipani}, P. and 
	{Marty}, L. and {{\'A}lvarez}, F.~J. and {Apestigue}, V. and 
	{Bellucci}, G. and {Berthelier}, J.-J. and {Brucato}, J.~R. and 
	{Calcutt}, S.~B. and {Chiodini}, S. and {Cortecchia}, F. and 
	{Cozzolino}, F. and {Cucciarrè}, F. and {Deniskina}, N. and 
	{Déprez}, G. and {Di Achille}, G. and {Ferri}, F. and {Forget}, F. and 
	{Franzese}, G. and {Friso}, E. and {Genzer}, M. and {Hassen-Kodja}, R. and 
	{Haukka}, H. and {Hieta}, M. and {Jiménez}, J.~J. and {Josset}, J.-L. and 
	{Kahanp{\"a}{\"a}}, H. and {Karatekin}, O. and {Landis}, G. and 
	{Lapauw}, L. and {Lorenz}, R. and {Martinez-Oter}, J. and {Mennella}, V. and 
	{M{\"o}hlmann}, D. and {Moirin}, D. and {Molinaro}, R. and {Nikkanen}, T. and 
	{Palomba}, E. and {Patel}, M.~R. and {Pommereau}, J.-P. and 
	{Popa}, C.~I. and {Rafkin}, S. and {Rannou}, P. and {Renno}, N.~O. and 
	{Rivas}, J. and {Schmidt}, W. and {Segato}, E. and {Silvestro}, S. and 
	{Spiga}, A. and {Toledo}, D. and {Trautner}, R. and {Valero}, F. and 
	{V{\'a}zquez}, L. and {Vivat}, F. and {Witasse}, O. and {Yela}, M. and 
	{Mugnuolo}, R. and {Marchetti}, E. and {Pirrotta}, S.},
  title = {{The DREAMS Experiment Onboard the Schiaparelli Module of the ExoMars 2016 Mission: Design, Performances and Expected Results}},
  journal = {\ssr},
  keywords = {ExoMars, Schiaparelli, DREAMS, Mars, Atmospheric electric field, Meteorological station, Dust storm season},
  year = 2018,
  volume = 214,
  eid = {103},
  pages = {103},
  abstract = {{The first of the two missions foreseen in the ExoMars program was
successfully launched on 14th March 2016. It included the Trace Gas
Orbiter and the Schiaparelli Entry descent and landing Demonstrator
Module. Schiaparelli hosted the DREAMS instrument suite that was the
only scientific payload designed to operate after the touchdown. DREAMS
is a meteorological station with the capability of measuring the
electric properties of the Martian atmosphere. It was a completely
autonomous instrument, relying on its internal battery for the power
supply. Even with low resources (mass, energy), DREAMS would be able to
perform novel measurements on Mars (atmospheric electric field) and
further our understanding of the Martian environment, including the dust
cycle. DREAMS sensors were designed to operate in a very dusty
environment, because the experiment was designed to operate on Mars
during the dust storm season (October 2016 in Meridiani Planum).
Unfortunately, the Schiaparelli module failed part of the descent and
the landing and crashed onto the surface of Mars. Nevertheless, several
seconds before the crash, the module central computer switched the
DREAMS instrument on, and sent back housekeeping data indicating that
the DREAMS sensors were performing nominally. This article describes the
instrument in terms of scientific goals, design, working principle and
performances, as well as the results of calibration and field tests. The
spare model is mature and available to fly in a future mission.
  doi = {10.1007/s11214-018-0535-0},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Golombek}, M. and {Grott}, M. and {Kargl}, G. and {Andrade}, J. and 
	{Marshall}, J. and {Warner}, N. and {Teanby}, N.~A. and {Ansan}, V. and 
	{Hauber}, E. and {Voigt}, J. and {Lichtenheldt}, R. and {Knapmeyer-Endrun}, B. and 
	{Daubar}, I.~J. and {Kipp}, D. and {Muller}, N. and {Lognonné}, P. and 
	{Schmelzbach}, C. and {Banfield}, D. and {Trebi-Ollennu}, A. and 
	{Maki}, J. and {Kedar}, S. and {Mimoun}, D. and {Murdoch}, N. and 
	{Piqueux}, S. and {Delage}, P. and {Pike}, W.~T. and {Charalambous}, C. and 
	{Lorenz}, R. and {Fayon}, L. and {Lucas}, A. and {Rodriguez}, S. and 
	{Morgan}, P. and {Spiga}, A. and {Panning}, M. and {Spohn}, T. and 
	{Smrekar}, S. and {Gudkova}, T. and {Garcia}, R. and {Giardini}, D. and 
	{Christensen}, U. and {Nicollier}, T. and {Sollberger}, D. and 
	{Robertsson}, J. and {Ali}, K. and {Kenda}, B. and {Banerdt}, W.~B.
  title = {{Geology and Physical Properties Investigations by the InSight Lander}},
  journal = {\ssr},
  keywords = {InSight, Mars, Geology, Physical properties, Surface materials},
  year = 2018,
  volume = 214,
  eid = {84},
  pages = {84},
  abstract = {{Although not the prime focus of the InSight mission, the near-surface
geology and physical properties investigations provide critical
information for both placing the instruments (seismometer and heat flow
probe with mole) on the surface and for understanding the nature of the
shallow subsurface and its effect on recorded seismic waves. Two color
cameras on the lander will obtain multiple stereo images of the surface
and its interaction with the spacecraft. Images will be used to identify
the geologic materials and features present, quantify their areal
coverage, help determine the basic geologic evolution of the area, and
provide ground truth for orbital remote sensing data. A radiometer will
measure the hourly temperature of the surface in two spots, which will
determine the thermal inertia of the surface materials present and their
particle size and/or cohesion. Continuous measurements of wind speed and
direction offer a unique opportunity to correlate dust devils and high
winds with eolian changes imaged at the surface and to determine the
threshold friction wind stress for grain motion on Mars. During the
first two weeks after landing, these investigations will support the
selection of instrument placement locations that are relatively smooth,
flat, free of small rocks and load bearing. Soil mechanics parameters
and elastic properties of near surface materials will be determined from
mole penetration and thermal conductivity measurements from the surface
to 3-5 m depth, the measurement of seismic waves during mole hammering,
passive monitoring of seismic waves, and experiments with the arm and
scoop of the lander (indentations, scraping and trenching). These
investigations will determine and test the presence and mechanical
properties of the expected 3-17 m thick fragmented regolith (and
underlying fractured material) built up by impact and eolian processes
on top of Hesperian lava flows and determine its seismic properties for
the seismic investigation of Mars' interior.
  doi = {10.1007/s11214-018-0512-7},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Hartmann}, J.-M. and {Tran}, H. and {Armante}, R. and {Boulet}, C. and 
	{Campargue}, A. and {Forget}, F. and {Gianfrani}, L. and {Gordon}, I. and 
	{Guerlet}, S. and {Gustafsson}, M. and {Hodges}, J.~T. and {Kassi}, S. and 
	{Lisak}, D. and {Thibault}, F. and {Toon}, G.~C.},
  title = {{Recent advances in collisional effects on spectra of molecular gases and their practical consequences}},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  keywords = {Pressure effects on spectral shapes, Experimental techniques, Theories and models, Available data, Consequences for applications},
  year = 2018,
  volume = 213,
  pages = {178-227},
  abstract = {{We review progress, since publication of the book ``Collisional effects
on molecular spectra: Laboratory experiments and models, consequences
for applications`` (Elsevier, Amsterdam, 2008), on measuring, modeling
and predicting the influence of pressure (ie of intermolecular
collisions) on the spectra of gas molecules. We first introduce recently
developed experimental techniques of high accuracy and sensitivity. We
then complement the aforementioned book by presenting the theoretical
approaches, results and data proposed (mostly) in the last decade on the
topics of isolated line shapes, line-broadening and -shifting,
line-mixing, the far wings and associated continua, and
collision-induced absorption. Examples of recently demonstrated
consequences of the progress in the description of spectral shapes for
some practical applications (metrology, probing of gas media, climate
predictions) are then given. Remaining issues and directions for future
research are finally discussed.
  doi = {10.1016/j.jqsrt.2018.03.016},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Gonz{\'a}lez-Galindo}, F. and {Chaufray}, J.-Y. and {Forget}, F. and 
	{Garc{\'{\i}}a-Comas}, M. and {Montmessin}, F. and {Jain}, S.~K. and 
	{Stiepen}, A.},
  title = {{UV Dayglow Variability on Mars: Simulation With a Global Climate Model and Comparison With SPICAM/MEx Data}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars, dayglow, global modeling, Mars Express},
  year = 2018,
  volume = 123,
  pages = {1934-1952},
  abstract = {{A model able to simulate the CO Cameron bands and the
CO$_{2}$$^{+}$ UV doublet, two of the most prominent UV
emissions in the Martian dayside, has been incorporated into a Mars
global climate model. The model self-consistently quantifies the effects
of atmospheric variability on the simulated dayglow for the first time.
Comparison of the modeled peak intensities with Mars Express (MEx)
SPICAM (Spectroscopy for Investigation of Characteristics of the
Atmosphere of Mars) observations confirms previous suggestions that
electron impact cross sections on CO$_{2}$ and CO need to be
reduced. The peak altitudes are well predicted by the model, except for
the period of MY28 characterized by the presence of a global dust storm.
Global maps of the simulated emission systems have been produced,
showing a seasonal variability of the peak intensities dominated by the
eccentricity of the Martian orbit. A significant contribution of the CO
electron impact excitation to the Cameron bands is found, with
variability linked to that of the CO abundance. This is in disagreement
with previous theoretical models, due to the larger CO abundance
predicted by our model. In addition, the contribution of this process
increases with altitude, indicating that care should be taken when
trying to derive temperatures from the scale height of this emission.
The analysis of the geographical variability of the predicted
intensities reflects the predicted density variability. In particular, a
longitudinal variability dominated by a wave-3 pattern is obtained both
in the predicted density and in the predicted peak altitudes.
  doi = {10.1029/2018JE005556},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Bertrand}, T. and {Forget}, F. and {Umurhan}, O.~M. and {Grundy}, W.~M. and 
	{Schmitt}, B. and {Protopapa}, S. and {Zangari}, A.~M. and {White}, O.~L. and 
	{Schenk}, P.~M. and {Singer}, K.~N. and {Stern}, A. and {Weaver}, H.~A. and 
	{Young}, L.~A. and {Ennico}, K. and {Olkin}, C.~B.},
  title = {{The nitrogen cycles on Pluto over seasonal and astronomical timescales}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1804.02434},
  primaryclass = {astro-ph.EP},
  keywords = {Pluto, Nitrogen, Paleo, Modeling, GCM, Sputnik Planitia},
  year = 2018,
  volume = 309,
  pages = {277-296},
  abstract = {{Pluto's landscape is shaped by the endless condensation and sublimation
cycles of the volatile ices covering its surface. In particular, the
Sputnik Planitia ice sheet, which is thought to be the main reservoir of
nitrogen ice, displays a large diversity of terrains, with bright and
dark plains, small pits and troughs, topographic depressions and
evidences of recent and past glacial flows. Outside Sputnik Planitia,
New Horizons also revealed numerous nitrogen ice deposits, in the
eastern side of Tombaugh Regio and at mid-northern latitudes.

These observations suggest a complex history involving volatile and
glacial processes occurring on different timescales. We present
numerical simulations of volatile transport on Pluto performed with a
model designed to simulate the nitrogen cycle over millions of years,
taking into account the changes of obliquity, solar longitude of
perihelion and eccentricity as experienced by Pluto. Using this model,
we first explore how the volatile and glacial activity of nitrogen
within Sputnik Planitia has been impacted by the diurnal, seasonal and
astronomical cycles of Pluto. Results show that the obliquity dominates
the N$_{2}$ cycle and that over one obliquity cycle, the latitudes
of Sputnik Planitia between 25{\deg}S-30{\deg}N are dominated by
N$_{2}$ condensation, while the northern regions between 30{\deg}N
and -50{\deg}N are dominated by N$_{2}$ sublimation. We find that a
net amount of 1 km of ice has sublimed at the northern edge of Sputnik
Planitia during the last 2 millions of years. It must have been
compensated by a viscous flow of the thick ice sheet. By comparing these
results with the observed geology of Sputnik Planitia, we can relate the
formation of the small pits and the brightness of the ice at the center
of Sputnik Planitia to the sublimation and condensation of ice occurring
at the annual timescale, while the glacial flows at its eastern edge and
the erosion of the water ice mountains all around the ice sheet are
instead related to the astronomical timescale. We also perform
simulations including a glacial flow scheme which shows that the Sputnik
Planitia ice sheet is currently at its minimum extent at the northern
and southern edges. We also explore the stability of N$_{2}$ ice
deposits outside the latitudes and longitudes of the Sputnik Planitia
basin. Results show that N$_{2}$ ice is not stable at the poles
but rather in the equatorial regions, in particular in depressions,
where thick deposits may persist over tens of millions of years, before
being trapped in Sputnik Planitia. Finally, another key result is that
the minimum and maximum surface pressures obtained over the simulated
millions of years remain in the range of milli-Pascals and Pascals,
respectively. This suggests that Pluto never encountered conditions
allowing liquid nitrogen to flow directly on its surface. Instead, we
suggest that the numerous geomorphological evidences of past liquid flow
observed on Pluto's surface are the result of liquid nitrogen that
flowed at the base of thick ancient nitrogen glaciers, which have since
  doi = {10.1016/j.icarus.2018.03.012},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Spiga}, A. and {Smith}, I.},
  title = {{Katabatic jumps in the Martian northern polar regions}},
  journal = {\icarus},
  year = 2018,
  volume = 308,
  pages = {197-208},
  abstract = {{Martian polar regions host active regional wind circulations, such as
the downslope katabatic winds which develop owing to near-surface
radiative cooling and sloped topography. Many observations (stratigraphy
from radar profiling, frost streaks, spectral analysis of ices) concur
to show that aeolian processes play a key role in glacial processes in
Martian polar regions. A spectacular manifestation of this resides in
elongated clouds that forms within the polar spiral troughs, a series of
geological depressions in Mars' polar caps. Here we report mesoscale
atmospheric modeling in Martian polar regions making use of five nested
domains operating a model downscaling from horizontal resolutions of
twenty kilometers to 200 m in a typical polar trough. We show that
strong katabatic jumps form at the bottom of polar troughs with an
horizontal morphology and location similar to trough clouds, large
vertical velocity (up to +3 m/s) and temperature perturbations (up to 20
K) propitious to cloud formation. This strongly suggests that trough
clouds on Mars are caused by katabatic jumps forming within polar
troughs. This phenomena is analogous to the terrestrial Loewe phenomena
over Antarctica's slopes and coastlines, resulting in a distinctive
``wall of snow'' during katabatic events. Our mesoscale modeling results
thereby suggest that trough clouds might be present manifestations of
the ice migration processes that yielded the internal cap structure
discovered by radar observations, as part of a ``cyclic step'' process.
This has important implications for the stability and possible migration
over geological timescales of water ice surface reservoirs-and, overall,
for the evolution of Mars' polar caps over geological timescales.
  doi = {10.1016/j.icarus.2017.10.021},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Smith}, I.~B. and {Spiga}, A.},
  title = {{Seasonal variability in winds in the north polar region of Mars}},
  journal = {\icarus},
  year = 2018,
  volume = 308,
  pages = {188-196},
  abstract = {{Surface features near Mars' polar regions are very active, suggesting
that they are among the most dynamic places on the planet. Much of that
activity is driven by seasonal winds that strongly influence the
distribution of water ice and other particulates. Morphologic features
such as the spiral troughs, Chasma Boreale, and prominent circumpolar
dune fields have experienced persistent winds for several Myr.
Therefore, detailing the pattern of winds throughout the year is an
important step to understanding what processes affect the martian
surface in contemporary and past epochs. In this study, we provide
polar-focused mesoscale simulations from northern spring to summer to
understand variability from the diurnal to the seasonal scales. We find
that there is a strong seasonality to the diurnal surface wind speeds
driven primarily by the retreat of the seasonal CO$_{2}$ until
about summer solstice, when the CO$_{2}$ is gone. The fastest
winds are found when the CO$_{2}$ cap boundary is on the slopes of
the north polar layered deposits, providing a strong thermal gradient
that enhances the season-long katabatic effect. Mid-summer winds, while
not as fast as spring winds, may play a role in dune migration for some
dune fields. Late summer wind speeds pick up as the seasonal cap
  doi = {10.1016/j.icarus.2017.10.005},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Guallini}, L. and {Rossi}, A.~P. and {Forget}, F. and {Marinangeli}, L. and 
	{Lauro}, S.~E. and {Pettinelli}, E. and {Seu}, R. and {Thomas}, N.
  title = {{Regional stratigraphy of the south polar layered deposits (Promethei Lingula, Mars): ``Discontinuity-bounded'' units in images and radargrams}},
  journal = {\icarus},
  keywords = {Geological processes, Mars, polar geology, surface, Image processing},
  year = 2018,
  volume = 308,
  pages = {76-107},
  abstract = {{The Mars South Polar Layered Deposits (SPLD) are the result of
depositional and erosional events, which are marked by different
stratigraphic sequences and erosional surfaces. To unambiguously define
the stratigraphic units at regional scale, we mapped the SPLD on the
basis of observed discontinuities (i.e., unconformities, correlative
discontinuities and conformities), as commonly done in terrestrial
modern stratigraphy. This methodology is defined as
``Discontinuity-Bounded Units'' or allostratigraphy, and is complemented
by geomorphological mapping.

Our study focuses on Promethei Lingula (PL) and uses both
high-resolution images (CTX, HiRISE) and radargrams (SHARAD) to combine
surface and sub-surface observations and obtain a 3D geological
reconstruction of the SPLD. One regional discontinuity (named AUR1) was
defined within the studied stratigraphic succession and is exposed in
several non-contiguous outcrops around PL as well as observed at depth
within the ice sheet. This is the primary contact between two major
depositional sequences, showing a different texture at CTX resolution.
The lower sequence is characterized mainly by a ``ridge and trough''
morphology (Ridge and Trough Sequence; RTS) and the upper sequence shows
mainly by a ``stair-stepped'' morphology (Stair-Stepped Sequence; SSS). On
the basis of the observations, we defined two regional
``discontinuity-bounded'' units in PL, respectively coinciding with RTS
and SSS sequences. Our stratigraphic reconstruction provides new hints
on the major scale events that shaped this region. Oscillations in
Martian axial obliquity could have controlled local climate conditions
in the past, affecting the PL geological record.
  doi = {10.1016/j.icarus.2017.08.030},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Smith}, I.~B. and {Diniega}, S. and {Beaty}, D.~W. and {Thorsteinsson}, T. and 
	{Becerra}, P. and {Bramson}, A.~M. and {Clifford}, S.~M. and 
	{Hvidberg}, C.~S. and {Portyankina}, G. and {Piqueux}, S. and 
	{Spiga}, A. and {Titus}, T.~N.},
  title = {{6th international conference on Mars polar science and exploration: Conference summary and five top questions}},
  journal = {\icarus},
  year = 2018,
  volume = 308,
  pages = {2-14},
  abstract = {{We provide a historical context of the International Conference on Mars
Polar Science and Exploration and summarize the proceedings from the 6th
iteration of this meeting. In particular, we identify five key Mars
polar science questions based primarily on presentations and discussions
at the conference and discuss the overlap between some of those
questions. We briefly describe the seven scientific field trips that
were offered at the conference, which greatly supplemented conference
discussion of Mars polar processes and landforms. We end with
suggestions for measurements, modeling, and laboratory and field work
that were highlighted during conference discussion as necessary steps to
address key knowledge gaps.
  doi = {10.1016/j.icarus.2017.06.027},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Telfer}, M.~W. and {Parteli}, E.~J.~R. and {Radebaugh}, J. and 
	{Beyer}, R.~A. and {Bertrand}, T. and {Forget}, F. and {Nimmo}, F. and 
	{Grundy}, W.~M. and {Moore}, J.~M. and {Stern}, S.~A. and {Spencer}, J. and 
	{Lauer}, T.~R. and {Earle}, A.~M. and {Binzel}, R.~P. and {Weaver}, H.~A. and 
	{Olkin}, C.~B. and {Young}, L.~A. and {Ennico}, K. and {Runyon}, K. and 
  title = {{Dunes on Pluto}},
  journal = {Science},
  year = 2018,
  volume = 360,
  pages = {992-997},
  abstract = {{The surface of Pluto is more geologically diverse and dynamic than had
been expected, but the role of its tenuous atmosphere in shaping the
landscape remains unclear. We describe observations from the New
Horizons spacecraft of regularly spaced, linear ridges whose morphology,
distribution, and orientation are consistent with being transverse
dunes. These are located close to mountainous regions and are orthogonal
to nearby wind streaks. We demonstrate that the wavelength of the dunes
(\~{}0.4 to 1 kilometer) is best explained by the deposition of sand-sized
(\~{}200 to \~{}300 micrometer) particles of methane ice in moderate winds
($\lt$10 meters per second). The undisturbed morphology of the dunes, and
relationships with the underlying convective glacial ice, imply that the
dunes have formed in the very recent geological past.
  doi = {10.1126/science.aao2975},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Navarro}, T. and {Schubert}, G. and {Lebonnois}, S.},
  title = {{Atmospheric mountain wave generation on Venus and its influence on the solid planet's rotation rate}},
  journal = {Nature Geoscience},
  year = 2018,
  volume = 11,
  pages = {487-491},
  abstract = {{The Akatsuki spacecraft observed a 10,000-km-long meridional structure
at the top of the cloud deck of Venus that appeared stationary with
respect to the surface and was interpreted as a gravity wave.
Additionally, over four Venus solar days of observations, other such
waves were observed to appear in the afternoon over equatorial highland
regions. This indicates a direct influence of the solid planet on the
whole Venusian atmosphere despite dissimilar rotation rates of 243 and 4
days, respectively. How such gravity waves might be generated on Venus
is not understood. Here, we use general circulation model simulations of
the Venusian atmosphere to show that the observations are consistent
with stationary gravity waves over topographic highs{\mdash}or mountain
waves{\mdash}that are generated in the afternoon in equatorial regions by
the diurnal cycle of near-surface atmospheric stability. We find that
these mountain waves substantially contribute to the total atmospheric
torque that acts on the planet's surface. We estimate that mountain
waves, along with the thermal tide and baroclinic waves, can produce a
change in the rotation rate of the solid body of about 2 minutes per
solar day. This interplay between the solid planet and atmosphere may
explain some of the difference in rotation rates (equivalent to a change
in the length of day of about 7 minutes) measured by spacecraft over the
past 40 years.
  doi = {10.1038/s41561-018-0157-x},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Gr{\"o}ller}, H. and {Montmessin}, F. and {Yelle}, R.~V. and 
	{Lefèvre}, F. and {Forget}, F. and {Schneider}, N.~M. and 
	{Koskinen}, T.~T. and {Deighan}, J. and {Jain}, S.~K.},
  title = {{MAVEN/IUVS Stellar Occultation Measurements of Mars Atmospheric Structure and Composition}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {MAVEN/IUVS stellar occultations, atmospheric composition and structure, temperature profiles, waves/tides detection, ozone, molecular oxygen},
  year = 2018,
  volume = 123,
  pages = {1449-1483},
  abstract = {{The Imaging UltraViolet Spectrograph (IUVS) instrument of the Mars
Atmosphere and Volatile EvolutioN (MAVEN) mission has acquired data on
Mars for more than one Martian year. During this time, beginning with
March 2015, hundreds of stellar occultations have been observed, in 12
dedicated occultation campaigns, executed on average every 2 to 3
and the full range longitude and local times with relatively sparse
sampling. From these measurements we retrieve CO$_{2}$,
O$_{2}$, and O$_{3}$ number densities as well as temperature
profiles in the altitude range from 20 to 160 km, covering 8 orders of
magnitude in pressure from {\tilde}2 {\times} 10$^{1}$ to {\tilde}4
{\times} 10$^{-7}$ Pa. These data constrain the composition and
thermal structure of the atmosphere. The O$_{2}$ mixing ratios
retrieved during this study show a high variability from 1.5 {\times}
10$^{-3}$ to 6 {\times} 10$^{-3}$; however, the mean value
seems to be constant with solar longitude. We detect ozone between 20
and 60 km. In many profiles there is a well-defined peak between 30 and
40 km with a maximum density of 1-2 {\times}10$^{9}$
cm$^{-3}$. Examination of the vertical temperature profiles
reveals substantial disagreement with models, with observed temperatures
both warmer and colder than predicted. Examination of the altitude
profiles of density perturbations and their variation with longitude
shows structured atmospheric perturbations at altitudes above 100 km
that are likely nonmigrating tides. These perturbations are dominated by
zonal wave numbers 2 and 3 with amplitudes greater than 45\%.
  doi = {10.1029/2017JE005466},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Koskinen}, T.~T. and {Guerlet}, S.},
  title = {{Atmospheric structure and helium abundance on Saturn from Cassini/UVIS and CIRS observations}},
  journal = {\icarus},
  keywords = {Saturn, Occultations, Infrared observations, Atmospheres, Structure},
  year = 2018,
  volume = 307,
  pages = {161-171},
  abstract = {{We combine measurements from stellar occultations observed by the
Cassini Ultraviolet Imaging Spectrograph (UVIS) and limb scans observed
by the Composite Infrared Spectrometer (CIRS) to create empirical
atmospheric structure models for Saturn corresponding to the locations
probed by the occultations. The results cover multiple locations at low
to mid-latitudes between the spring of 2005 and the fall of 2015. We
connect the temperature-pressure (T-P) profiles retrieved from the CIRS
limb scans in the stratosphere to the T-P profiles in the thermosphere
retrieved from the UVIS occultations. We calculate the altitudes
corresponding to the pressure levels in each case based on our best fit
composition model that includes H$_{2}$, He, CH$_{4}$ and
upper limits on H. We match the altitude structure to the density
profile in the thermosphere that is retrieved from the occultations. Our
models depend on the abundance of helium and we derive a volume mixing
ratio of 11  {\plusmn}  2\% for helium in the lower atmosphere based on a
statistical analysis of the values derived for 32 different occultation
locations. We also derive the mean temperature and methane profiles in
the upper atmosphere and constrain their variability. Our results are
consistent with enhanced heating at the polar auroral region and a
dynamically active upper atmosphere.
  doi = {10.1016/j.icarus.2018.02.020},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Tran}, H. and {Turbet}, M. and {Chelin}, P. and {Landsheere}, X.
  title = {{Measurements and modeling of absorption by CO$_{2 }$+ H$_{2}$O mixtures in the spectral region beyond the CO$_{2}$ {$\nu$}$_{3}$-band head}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1802.01352},
  primaryclass = {astro-ph.EP},
  year = 2018,
  volume = 306,
  pages = {116-121},
  abstract = {{In this work, we measured the absorption by CO$_{2 }$+
H$_{2}$O mixtures from 2400 to 2600 cm$^{-1}$ which
corresponds to the spectral region beyond the {$\nu$}$_{3}$ band head
of CO$_{2}$. Transmission spectra of CO$_{2}$ mixed with
water vapor were recorded with a high-resolution Fourier-transform
spectrometer for various pressure, temperature and concentration
conditions. The continuum absorption by CO$_{2}$ due to the
presence of water vapor was determined by subtracting from measured
spectra the contribution of local lines of both species, that of the
continuum of pure CO$_{2}$ as well as of the self- and
CO$_{2}$-continua of water vapor induced by the
H$_{2}$O-H$_{2}$O and H$_{2}$O-CO$_{2}$
interactions. The obtained results are in very good agreement with the
unique previous measurement (in a narrower spectral range). They confirm
that the H$_{2}$O-continuum of CO$_{2}$ is significantly
larger than that observed for pure CO$_{2}$. This continuum thus
must be taken into account in radiative transfer calculations for media
involving CO$_{2}$+ H$_{2}$O mixture. An empirical model,
using sub-Lorentzian line shapes based on some temperature-dependent
correction factors {$\chi$} is proposed which enables an accurate
description of the experimental results.
  doi = {10.1016/j.icarus.2018.02.009},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Fernandez-Cascales}, L. and {Lucas}, A. and {Rodriguez}, S. and 
	{Gao}, X. and {Spiga}, A. and {Narteau}, C.},
  title = {{First quantification of relationship between dune orientation and sediment availability, Olympia Undae, Mars}},
  journal = {Earth and Planetary Science Letters},
  keywords = {Mars, dunes, bedform alignment, sediment cover, aeolian transport},
  year = 2018,
  volume = 489,
  pages = {241-250},
  abstract = {{Dunes provide unique information about wind regimes on planetary bodies
where there is no direct meteorological data. At the eastern margin of
Olympia Undae on Mars, dune orientation is measured from satellite
imagery and sediment cover is estimated using the high contrast between
the dune material and substrate. The analysis of these data provide the
first quantification of relationship between sediment availability and
dune orientation. Abrupt and smooth dune reorientations are associated
with inward and outward dynamics of dunes approaching and ejecting from
major sedimentary bodies, respectively. These reorientation patterns
along sediment transport pathways are interpreted using a new generation
dune model based on the coexistence of two dune growth mechanisms. This
model also permits solving of the inverse problem of predicting the wind
regime from dune orientation. For bidirectional wind regimes, solutions
of this inverse problem show substantial differences in the
distributions of sediment flux orientation, which can be attributed to
atmospheric flow variations induced by changes in albedo at the
boundaries of major dune fields. Then, we conclude that relationships
between sediment cover and dune orientation can be used to constrain
wind regime and dune field development on Mars and other planetary
  doi = {10.1016/j.epsl.2018.03.001},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Read}, P.~L. and {Lebonnois}, S.},
  title = {{Superrotation on Venus, on Titan, and Elsewhere}},
  journal = {Annual Review of Earth and Planetary Sciences},
  year = 2018,
  volume = 46,
  pages = {175-202},
  abstract = {{The superrotation of the atmospheres of Venus and Titan has puzzled
dynamicists for many years and seems to put these planets in a very
different dynamical regime from most other planets. In this review, we
consider how to define superrotation objectively and explore the
constraints that determine its occurrence. Atmospheric superrotation
also occurs elsewhere in the Solar System and beyond, and we compare
Venus and Titan with Earth and other planets for which wind estimates
are available. The extreme superrotation on Venus and Titan poses some
difficult challenges for numerical models of atmospheric circulation,
much more difficult than for more rapidly rotating planets such as Earth
or Mars. We consider mechanisms for generating and maintaining a
superrotating state, all of which involve a global meridional
overturning circulation. The role of nonaxisymmetric eddies is crucial,
however, but the detailed mechanisms may differ between Venus, Titan,
and other planets.
  doi = {10.1146/annurev-earth-082517-010137},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Grimm}, S.~L. and {Demory}, B.-O. and {Gillon}, M. and {Dorn}, C. and 
	{Agol}, E. and {Burdanov}, A. and {Delrez}, L. and {Sestovic}, M. and 
	{Triaud}, A.~H.~M.~J. and {Turbet}, M. and {Bolmont}, {\'E}. and 
	{Caldas}, A. and {de Wit}, J. and {Jehin}, E. and {Leconte}, J. and 
	{Raymond}, S.~N. and {Van Grootel}, V. and {Burgasser}, A.~J. and 
	{Carey}, S. and {Fabrycky}, D. and {Heng}, K. and {Hernandez}, D.~M. and 
	{Ingalls}, J.~G. and {Lederer}, S. and {Selsis}, F. and {Queloz}, D.
  title = {{The nature of the TRAPPIST-1 exoplanets}},
  journal = {\aap},
  archiveprefix = {arXiv},
  eprint = {1802.01377},
  primaryclass = {astro-ph.EP},
  keywords = {methods: numerical, planets and satellites: detection, planets and satellites: individual: TRAPPIST-1},
  year = 2018,
  volume = 613,
  eid = {A68},
  pages = {A68},
  abstract = {{Context. The TRAPPIST-1 system hosts seven Earth-sized, temperate
exoplanets orbiting an ultra-cool dwarf star. As such, it represents a
remarkable setting to study the formation and evolution of terrestrial
planets that formed in the same protoplanetary disk. While the sizes of
the TRAPPIST-1 planets are all known to better than 5\% precision, their
densities have significant uncertainties (between 28\% and 95\%) because
of poor constraints on the planet's masses. 
Aims: The goal of this paper is to improve our knowledge of the TRAPPIST-1 planetary masses and densities using transit-timing variations (TTVs). The complexity of the TTV inversion problem is known to be particularly acute in multi-planetary systems (convergence issues, degeneracies and size of the parameter space), especially for resonant chain systems such as TRAPPIST-1.
Methods: To overcome these challenges, we have used a novel method that employs a genetic algorithm coupled to a full N-body integrator that we applied to a set of 284 individual transit timings. This approach enables us to efficiently explore the parameter space and to derive reliable masses and densities from TTVs for all seven planets.
Results: Our new masses result in a five- to eight-fold improvement on the planetary density uncertainties, with precisions ranging from 5\% to 12\%. These updated values provide new insights into the bulk structure of the TRAPPIST-1 planets. We find that TRAPPIST-1 c and e likely have largely rocky interiors, while planets b, d, f, g, and h require envelopes of volatiles in the form of thick atmospheres, oceans, or ice, in most cases with water mass fractions less than 5\%. }}, doi = {10.1051/0004-6361/201732233}, adsurl = {}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }
  author = {{Turbet}, M. and {Bolmont}, E. and {Leconte}, J. and {Forget}, F. and 
	{Selsis}, F. and {Tobie}, G. and {Caldas}, A. and {Naar}, J. and 
	{Gillon}, M.},
  title = {{Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets}},
  journal = {\aap},
  archiveprefix = {arXiv},
  eprint = {1707.06927},
  primaryclass = {astro-ph.EP},
  keywords = {stars: individual: TRAPPIST-1, planets and satellites: terrestrial planets, planets and satellites: atmospheres, planets and satellites: dynamical evolution and stability, astrobiology},
  year = 2018,
  volume = 612,
  eid = {A86},
  pages = {A86},
  abstract = {{TRAPPIST-1 planets are invaluable for the study of comparative planetary
science outside our solar system and possibly habitability. Both transit
timing variations (TTV) of the planets and the compact, resonant
architecture of the system suggest that TRAPPIST-1 planets could be
endowed with various volatiles today. First, we derived from N-body
simulations possible planetary evolution scenarios, and show that all
the planets are likely in synchronous rotation. We then used a versatile
3D global climate model (GCM) to explore the possible climates of cool
planets around cool stars, with a focus on the TRAPPIST-1 system. We
investigated the conditions required for cool planets to prevent
possible volatile species to be lost permanently by surface
condensation, irreversible burying or photochemical destruction. We also
explored the resilience of the same volatiles (when in condensed phase)
to a runaway greenhouse process. We find that background atmospheres
made of N$_{2}$, CO, or O$_{2}$ are rather resistant to
atmospheric collapse. However, even if TRAPPIST-1 planets were able to
sustain a thick background atmosphere by surviving early X/EUV radiation
and stellar wind atmospheric erosion, it is difficult for them to
accumulate significant greenhouse gases like CO$_{2}$,
CH$_{4}$, or NH$_{3}$. CO$_{2}$ can easily condense on
the permanent nightside, forming CO$_{2}$ ice glaciers that would
flow toward the substellar region. A complete CO$_{2}$ ice surface
cover is theoretically possible on TRAPPIST-1g and h only, but
CO$_{2}$ ices should be gravitationally unstable and get buried
beneath the water ice shell in geologically short timescales. Given
TRAPPIST-1 planets large EUV irradiation (at least  10$^{3}$
{\times} Titan's flux), CH$_{4}$ and NH$_{3}$ are
photodissociated rapidly and are thus hard to accumulate in the
atmosphere. Photochemical hazes could then sedimentate and form a
surface layer of tholins that would progressively thicken over the age
of the TRAPPIST-1 system. Regarding habitability, we confirm that few
bars of CO$_{2}$ would suffice to warm the surface of TRAPPIST-1f
and g above the melting point of water. We also show that TRAPPIST-1e is
a remarkable candidate for surface habitability. If the planet is today
synchronous and abundant in water, then it should very likely sustain
surface liquid water at least in the substellar region, whatever the
atmosphere considered.
  doi = {10.1051/0004-6361/201731620},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Wang}, C. and {Forget}, F. and {Bertrand}, T. and {Spiga}, A. and 
	{Millour}, E. and {Navarro}, T.},
  title = {{Parameterization of Rocket Dust Storms on Mars in the LMD Martian GCM: Modeling Details and Validation}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {rocket dust storm, detached dust layers, parameterization, LMD Martian GCM, MCS},
  year = 2018,
  volume = 123,
  pages = {982-1000},
  abstract = {{The origin of the detached dust layers observed by the Mars Climate
Sounder aboard the Mars Reconnaissance Orbiter is still debated. Spiga
et al. (2013,
revealed that deep mesoscale convective ``rocket dust storms'' are likely
to play an important role in forming these dust layers. To investigate
how the detached dust layers are generated by this mesoscale phenomenon
and subsequently evolve at larger scales, a parameterization of rocket
dust storms to represent the mesoscale dust convection is designed and
included into the Laboratoire de Météorologie Dynamique
(LMD) Martian Global Climate Model (GCM). The new parameterization
allows dust particles in the GCM to be transported to higher altitudes
than in traditional GCMs. Combined with the horizontal transport by
large-scale winds, the dust particles spread out and form detached dust
layers. During the Martian dusty seasons, the LMD GCM with the new
parameterization is able to form detached dust layers. The formation,
evolution, and decay of the simulated dust layers are largely in
agreement with the Mars Climate Sounder observations. This suggests that
mesoscale rocket dust storms are among the key factors to explain the
observed detached dust layers on Mars. However, the detached dust layers
remain absent in the GCM during the clear seasons, even with the new
parameterization. This implies that other relevant atmospheric
processes, operating when no dust storms are occurring, are needed to
explain the Martian detached dust layers. More observations of local
dust storms could improve the ad hoc aspects of this parameterization,
such as the trigger and timing of dust injection.
  doi = {10.1002/2017JE005255},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Singh}, D. and {Flanner}, M.~G. and {Millour}, E.},
  title = {{Improvement of Mars Surface Snow Albedo Modeling in LMD Mars GCM With SNICAR}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars, snow modeling, cryosphere, LMD Mars GCM},
  year = 2018,
  volume = 123,
  pages = {780-791},
  abstract = {{The current version of Laboratoire de Météorologie
Dynamique (LMD) Mars GCM (original-MGCM) uses annually repeating
(prescribed) CO$_{2}$ snow albedo values based on the Thermal
Emission Spectrometer observations. We integrate the Snow, Ice, and
Aerosol Radiation (SNICAR) model with MGCM (SNICAR-MGCM) to
prognostically determine H$_{2}$O and CO$_{2}$ snow albedos
interactively in the model. Using the new diagnostic capabilities of
this model, we find that cryospheric surfaces (with dust) increase the
global surface albedo of Mars by 0.022. Over snow-covered regions,
SNICAR-MGCM simulates mean albedo that is higher by about 0.034 than
prescribed values in the original-MGCM. Globally, shortwave flux into
the surface decreases by 1.26 W/m$^{2}$, and net CO$_{2}$
snow deposition increases by about 4\% with SNICAR-MGCM over one Martian
annual cycle as compared to the original-MGCM simulations. SNICAR
integration reduces the mean global surface temperature and the surface
pressure of Mars by about 0.87\% and 2.5\%, respectively. Changes in
albedo also show a similar distribution to dust deposition over the
globe. The SNICAR-MGCM model generates albedos with higher sensitivity
to surface dust content as compared to original-MGCM. For snow-covered
regions, we improve the correlation between albedo and optical depth of
dust from -0.91 to -0.97 with SNICAR-MGCM as compared to the
original-MGCM. Dust substantially darkens Mars's cryosphere, thereby
reducing its impact on the global shortwave energy budget by more than
half, relative to the impact of pure snow.
  doi = {10.1002/2017JE005368},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Chaufray}, J.-Y. and {Yelle}, R.~V. and {Gonzalez-Galindo}, F. and 
	{Forget}, F. and {Lopez-Valverde}, M. and {Leblanc}, F. and 
	{Modolo}, R.},
  title = {{Effect of the Lateral Exospheric Transport on the Horizontal Hydrogen Distribution Near the Exobase of Mars}},
  journal = {Journal of Geophysical Research (Space Physics)},
  keywords = {Mars, exosphere, hydrogen},
  year = 2018,
  volume = 123,
  pages = {2441-2454},
  abstract = {{We simulate the hydrogen density near the exobase of Mars, using the 3-D
Martian Global Circulation Model of Laboratoire de
Météorologie Dynamique, coupled to an exospheric ballistic
model to compute the downward ballistic flux. The simulated hydrogen
distribution near the exobase obtained at two different seasons{\mdash}Ls
= 180{\deg} and Ls = 270{\deg}{\mdash}is close to Zero Net Ballistic Flux
equilibrium. In other words, the hydrogen density near the exobase
adjusts to have a balance between the local upward ballistic and the
downward ballistic flux due to a short lateral migration time in the
exosphere compared to the vertical diffusion time. This equilibrium
leads to a hydrogen density n near the exobase directly controlled by
the exospheric temperature T by the relation nT$^{5/2}$ =
constant. This relation could be used to extend 1-D hydrogen exospheric
model of Mars used to derive the hydrogen density and escape flux at
Mars from Lyman-{$\alpha$} observations to 3-D model based on observed or
modeled exospheric temperature near the exobase, without increasing the
number of free parameters.
  doi = {10.1002/2017JA025163},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Korablev}, O. and {Montmessin}, F. and {Trokhimovskiy}, A. and 
	{Fedorova}, A.~A. and {Shakun}, A.~V. and {Grigoriev}, A.~V. and 
	{Moshkin}, B.~E. and {Ignatiev}, N.~I. and {Forget}, F. and 
	{Lefèvre}, F. and {Anufreychik}, K. and {Dzuban}, I. and 
	{Ivanov}, Y.~S. and {Kalinnikov}, Y.~K. and {Kozlova}, T.~O. and 
	{Kungurov}, A. and {Makarov}, V. and {Martynovich}, F. and {Maslov}, I. and 
	{Merzlyakov}, D. and {Moiseev}, P.~P. and {Nikolskiy}, Y. and 
	{Patrakeev}, A. and {Patsaev}, D. and {Santos-Skripko}, A. and 
	{Sazonov}, O. and {Semena}, N. and {Semenov}, A. and {Shashkin}, V. and 
	{Sidorov}, A. and {Stepanov}, A.~V. and {Stupin}, I. and {Timonin}, D. and 
	{Titov}, A.~Y. and {Viktorov}, A. and {Zharkov}, A. and {Altieri}, F. and 
	{Arnold}, G. and {Belyaev}, D.~A. and {Bertaux}, J.~L. and {Betsis}, D.~S. and 
	{Duxbury}, N. and {Encrenaz}, T. and {Fouchet}, T. and {Gérard}, J.-C. and 
	{Grassi}, D. and {Guerlet}, S. and {Hartogh}, P. and {Kasaba}, Y. and 
	{Khatuntsev}, I. and {Krasnopolsky}, V.~A. and {Kuzmin}, R.~O. and 
	{Lellouch}, E. and {Lopez-Valverde}, M.~A. and {Luginin}, M. and 
	{M{\"a}{\"a}tt{\"a}nen}, A. and {Marcq}, E. and {Martin Torres}, J. and 
	{Medvedev}, A.~S. and {Millour}, E. and {Olsen}, K.~S. and {Patel}, M.~R. and 
	{Quantin-Nataf}, C. and {Rodin}, A.~V. and {Shematovich}, V.~I. and 
	{Thomas}, I. and {Thomas}, N. and {Vazquez}, L. and {Vincendon}, M. and 
	{Wilquet}, V. and {Wilson}, C.~F. and {Zasova}, L.~V. and {Zelenyi}, L.~M. and 
	{Zorzano}, M.~P.},
  title = {{The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter}},
  journal = {\ssr},
  keywords = {Mars, Atmosphere, High-resolution spectrometer, Fourier-spectrometer, Echelle, Cross-dispersion},
  year = 2018,
  volume = 214,
  eid = {7},
  pages = {7},
  abstract = {{The Atmospheric Chemistry Suite (ACS) package is an element of the
Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter
(TGO) mission. ACS consists of three separate infrared spectrometers,
sharing common mechanical, electrical, and thermal interfaces. This
ensemble of spectrometers has been designed and developed in response to
the Trace Gas Orbiter mission objectives that specifically address the
requirement of high sensitivity instruments to enable the unambiguous
detection of trace gases of potential geophysical or biological
interest. For this reason, ACS embarks a set of instruments achieving
simultaneously very high accuracy (ppt level), very high resolving power
($\gt$10,000) and large spectral coverage (0.7 to 17 {$\mu$}m{\mdash}the
visible to thermal infrared range). The near-infrared (NIR) channel is a
versatile spectrometer covering the 0.7-1.6 {$\mu$}m spectral range with a
resolving power of {\tilde}20,000. NIR employs the combination of an
echelle grating with an AOTF (Acousto-Optical Tunable Filter) as
diffraction order selector. This channel will be mainly operated in
solar occultation and nadir, and can also perform limb observations. The
scientific goals of NIR are the measurements of water vapor, aerosols,
and dayside or night side airglows. The mid-infrared (MIR) channel is a
cross-dispersion echelle instrument dedicated to solar occultation
measurements in the 2.2-4.4 {$\mu$}m range. MIR achieves a resolving power
of $\gt$50,000. It has been designed to accomplish the most sensitive
measurements ever of the trace gases present in the Martian atmosphere.
The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum
Fourier-transform spectrometer encompassing the spectral range of 1.7-17
{$\mu$}m with apodized resolution varying from 0.2 to 1.3 cm$^{-1}$.
TIRVIM is primarily dedicated to profiling temperature from the surface
up to {\tilde}60 km and to monitor aerosol abundance in nadir. TIRVIM
also has a limb and solar occultation capability. The technical concept
of the instrument, its accommodation on the spacecraft, the optical
designs as well as some of the calibrations, and the expected
performances for its three channels are described.
  doi = {10.1007/s11214-017-0437-6},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Chaufray}, J.-Y. and {Gonzalez-Galindo}, F. and {Forget}, F. and 
	{Lopez-Valverde}, M. and {Leblanc}, F. and {Modolo}, R. and 
	{Hess}, S.},
  title = {{Reply to comment ``On the hydrogen escape: Comment to variability of the hydrogen in the Martian upper atmosphere as simulated by a 3D atmosphere-exosphere coupling by J.-Y. Chaufray et al.'' by V. Krasnopolsky, Icarus, 281, 262}},
  journal = {\icarus},
  year = 2018,
  volume = 301,
  pages = {132-135},
  abstract = {{Krasnopolsky (2017) makes a careful review of our recent results about
the Martian hydrogen content of the Martian upper atmosphere (Chaufray
et al., 2015). We comment here on his two major points. First, he
suggests that the non-thermal escape of H$_{2}$, and particularly
collisions with hot oxygen, not taken into account in our general
circulation model (GCM), should modify our reported H$_{2}$ and H
density profiles. This is an important issue; we acknowledge that future
effective coupling of our GCM with comprehensive models of the Martian
solar wind interaction, ideally after being validated with the latest
plasma observations of H$_{2}$$^{+}$, would allow for better
estimations of the relative importance of the H$_{2}$ non-thermal
and thermal escape processes. For the time being we need assumptions in
the GCM, with proper and regular updates. According to a recent and
detailed study of the anisotropic elastic and inelastic collision cross
sections between O and H$_{2}$ (Gacesa et al., 2012), the escape
rates used by Krasnopolsky (2010) for this process might be
overestimated. We therefore do not include non thermal escape of
H$_{2}$ in the model. And secondly, in response to Krasnopolsky's
comment on the H escape variability with the solar cycle, we revised our
calculations and found a small bug in the computation of the Jeans
effusion velocity. Our revised computed H escape rates are included
here. They have a small impact on our key conclusions: similar seasonal
variations, a reduced variation with the solar cycle but still larger
than Krasnopolsky (2017), and again a hydrogen scape systematically
lower than the diffusion-limited flux. This bug does not affect the
latest Mars Climate Database v5.2.
  doi = {10.1016/j.icarus.2017.07.013},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Erard}, S. and {Cecconi}, B. and {Le Sidaner}, P. and {Rossi}, A.~P. and 
	{Capria}, M.~T. and {Schmitt}, B. and {Génot}, V. and {André}, N. and 
	{Vandaele}, A.~C. and {Scherf}, M. and {Hueso}, R. and {M{\"a}{\"a}tt{\"a}nen}, A. and 
	{Thuillot}, W. and {Carry}, B. and {Achilleos}, N. and {Marmo}, C. and 
	{Santolik}, O. and {Benson}, K. and {Fernique}, P. and {Beigbeder}, L. and 
	{Millour}, E. and {Rousseau}, B. and {Andrieu}, F. and {Chauvin}, C. and 
	{Minin}, M. and {Ivanoski}, S. and {Longobardo}, A. and {Bollard}, P. and 
	{Albert}, D. and {Gangloff}, M. and {Jourdane}, N. and {Bouchemit}, M. and 
	{Glorian}, J.-M. and {Trompet}, L. and {Al-Ubaidi}, T. and {Juaristi}, J. and 
	{Desmars}, J. and {Guio}, P. and {Delaa}, O. and {Lagain}, A. and 
	{Soucek}, J. and {Pisa}, D.},
  title = {{VESPA: A community-driven Virtual Observatory in Planetary Science}},
  journal = {\planss},
  archiveprefix = {arXiv},
  eprint = {1705.09727},
  primaryclass = {astro-ph.IM},
  keywords = {Virtual Observatory, Solar System, GIS},
  year = 2018,
  volume = 150,
  pages = {65-85},
  abstract = {{The VESPA data access system focuses on applying Virtual Observatory
(VO) standards and tools to Planetary Science. Building on a previous
EC-funded Europlanet program, it has reached maturity during the first
year of a new Europlanet 2020 program (started in 2015 for 4 years). The
infrastructure has been upgraded to handle many fields of Solar System
studies, with a focus both on users and data providers. This paper
describes the broad lines of the current VESPA infrastructure as seen by
a potential user, and provides examples of real use cases in several
thematic areas. These use cases are also intended to identify hints for
future developments and adaptations of VO tools to Planetary Science.
  doi = {10.1016/j.pss.2017.05.013},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Guerlet}, S. and {Fouchet}, T. and {Spiga}, A. and {Flasar}, F.~M. and 
	{Fletcher}, L.~N. and {Hesman}, B.~E. and {Gorius}, N.},
  title = {{Equatorial Oscillation and Planetary Wave Activity in Saturn's Stratosphere Through the Cassini Epoch}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Saturn, Cassini, atmosphere, infrared remote sensing, stratospheric dynamics},
  year = 2018,
  volume = 123,
  pages = {246-261},
  abstract = {{Thermal infrared spectra acquired by Cassini/Composite InfraRed
Spectrometer (CIRS) in limb-viewing geometry in 2015 are used to derive
2-D latitude-pressure temperature and thermal wind maps. These maps are
used to study the vertical structure and evolution of Saturn's
equatorial oscillation (SEO), a dynamical phenomenon presenting
similarities with the Earth's quasi-biennal oscillation (QBO) and
semi-annual oscillation (SAO). We report that a new local wind maximum
has appeared in 2015 in the upper stratosphere and derive the descent
rates of other wind extrema through time. The phase of the oscillation
observed in 2015, as compared to 2005 and 2010, remains consistent with
a {\tilde}15 year period. The SEO does not propagate downward at a
regular rate but exhibits faster descent rate in the upper stratosphere,
combined with a greater vertical wind shear, compared to the lower
stratosphere. Within the framework of a QBO-type oscillation, we
estimate the absorbed wave momentum flux in the stratosphere to be on
the order of {\tilde}7 {\times} 10$^{-6}$ N m$^{-2}$. On
Earth, interactions between vertically propagating waves (both planetary
and mesoscale) and the mean zonal flow drive the QBO and SAO. To broaden
our knowledge on waves potentially driving Saturn's equatorial
oscillation, we searched for thermal signatures of planetary waves in
the tropical stratosphere using CIRS nadir spectra. Temperature
anomalies of amplitude 1-4 K and zonal wave numbers 1 to 9 are
frequently observed, and an equatorial Rossby (n = 1) wave of zonal wave
number 3 is tentatively identified in November 2009.
  doi = {10.1002/2017JE005419},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Moore}, J.~M. and {Howard}, A.~D. and {Umurhan}, O.~M. and 
	{White}, O.~L. and {Schenk}, P.~M. and {Beyer}, R.~A. and {McKinnon}, W.~B. and 
	{Spencer}, J.~R. and {Singer}, K.~N. and {Grundy}, W.~M. and 
	{Earle}, A.~M. and {Schmitt}, B. and {Protopapa}, S. and {Nimmo}, F. and 
	{Cruikshank}, D.~P. and {Hinson}, D.~P. and {Young}, L.~A. and 
	{Stern}, S.~A. and {Weaver}, H.~A. and {Olkin}, C.~B. and {Ennico}, K. and 
	{Collins}, G. and {Bertrand}, T. and {Forget}, F. and {Scipioni}, F. and 
	{New Horizons Science Team}},
  title = {{Bladed Terrain on Pluto: Possible origins and evolution}},
  journal = {\icarus},
  keywords = {Pluto, Atmosphere, Ices, Mechanical properties, Geological processes, IR spectroscopy, Surface},
  year = 2018,
  volume = 300,
  pages = {129-144},
  abstract = {{Bladed Terrain on Pluto consists of deposits of massive CH$_{4}$,
which are observed to occur within latitudes 30{\deg} of the equator and
are found almost exclusively at the highest elevations ($\gt$ 2 km above
the mean radius). Our analysis indicates that these deposits of
CH$_{4}$ preferentially precipitate at low latitudes where net
annual solar energy input is lowest. CH$_{4}$ and N$_{2}$
will both precipitate at low elevations. However, since there is much
more N$_{2}$ in the atmosphere than CH$_{4}$, the
N$_{2}$ ice will dominate at these low elevations. At high
elevations the atmosphere is too warm for N$_{2}$ to precipitate
so only CH$_{4}$ can do so. We conclude that following the time of
massive CH$_{4}$ emplacement; there have been sufficient
excursions in Pluto's climate to partially erode these deposits via
sublimation into the blades we see today. Blades composed of massive
CH$_{4}$ ice implies that the mechanical behavior of
CH$_{4}$ can support at least several hundred meters of relief at
Pluto surface conditions. Bladed Terrain deposits may be widespread in
the low latitudes of the poorly seen sub-Charon hemisphere, based on
spectral observations. If these locations are indeed Bladed Terrain
deposits, they may mark heretofore unrecognized regions of high
  doi = {10.1016/j.icarus.2017.08.031},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Sylvestre}, M. and {Teanby}, N.~A. and {Vinatier}, S. and {Lebonnois}, S. and 
	{Irwin}, P.~G.~J.},
  title = {{Seasonal evolution of C$_{2}$N$_{2}$, C$_{3}$H$_{4}$, and C$_{4}$H$_{2}$ abundances in Titan's lower stratosphere}},
  journal = {\aap},
  archiveprefix = {arXiv},
  eprint = {1709.09979},
  primaryclass = {astro-ph.EP},
  keywords = {planets and satellites: atmospheres, methods: data analysis},
  year = 2018,
  volume = 609,
  eid = {A64},
  pages = {A64},
  abstract = {{
Aims: We study the seasonal evolution of Titan's lower stratosphere (around 15 mbar) in order to better understand the atmospheric dynamics and chemistry in this part of the atmosphere.
Methods: We analysed Cassini/CIRS far-IR observations from 2006 to 2016 in order to measure the seasonal variations of three photochemical by-products: C$_{4}$H$_{2}$, C$_{3}$H$_{4}$, and C$_{2}$N$_{2}$.
Results: We show that the abundances of these three gases have evolved significantly at northern and southern high latitudes since 2006. We measure a sudden and steep increase of the volume mixing ratios of C$_{4}$H$_{2}$, C$_{3}$H$_{4}$, and C$_{2}$N$_{2}$ at the south pole from 2012 to 2013, whereas the abundances of these gases remained approximately constant at the north pole over the same period. At northern mid-latitudes, C$_{2}$N$_{2}$ and C$_{4}$H$_{2}$ abundances decrease after 2012 while C$_{3}$H$_{4}$ abundances stay constant. The comparison of these volume mixing ratio variations with the predictions of photochemical and dynamical models provides constraints on the seasonal evolution of atmospheric circulation and chemical processes at play. }}, doi = {10.1051/0004-6361/201630255}, adsurl = {}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }