@comment{{This file has been generated by bib2bib 1.94}}
@comment{{Command line: /usr/bin/bib2bib --quiet -c 'not journal:"Discussions"' -c year=2017 -c $type="ARTICLE" -oc pub2017.txt -ob pub2017.bib}}
  author = {{Leblanc}, F. and {Chaufray}, J.~Y. and {Modolo}, R. and {Leclercq}, L. and 
	{Curry}, S. and {Luhmann}, J. and {Lillis}, R. and {Hara}, T. and 
	{McFadden}, J. and {Halekas}, J. and {Schneider}, N. and {Deighan}, J. and 
	{Mahaffy}, P.~R. and {Benna}, M. and {Johnson}, R.~E. and {Gonzalez-Galindo}, F. and 
	{Forget}, F. and {Lopez-Valverde}, M.~A. and {Eparvier}, F.~G. and 
	{Jakosky}, B.},
  title = {{On the Origins of Mars' Exospheric Nonthermal Oxygen Component as Observed by MAVEN and Modeled by HELIOSARES}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars' atmospheric escape, MAVEN, exosphere},
  year = 2017,
  volume = 122,
  pages = {2401-2428},
  abstract = {{The first measurements of the emission brightness of the oxygen atomic
exosphere by Mars Atmosphere and Volatile EvolutioN (MAVEN) mission have
clearly shown that it is composed of a thermal component produced by the
extension of the upper atmosphere and of a nonthermal component.
Modeling these measurements allows us to constrain the origins of the
exospheric O and, as a consequence, to estimate Mars' present oxygen
escape rate. We here propose an analysis of three periods of MAVEN
observations based on a set of three coupled models: a hybrid
magnetospheric model (LATmos HYbrid Simulation (LatHyS)), an Exospheric
General Model (EGM), and the Global Martian Circulation model of the
Laboratoire de Météorologie Dynamique (LMD-GCM), which
provide a description of Mars' environment from the surface up to the
solar wind. The simulated magnetosphere by LatHyS is in good agreement
with MAVEN Plasma and Field Package instruments data. The LMD-GCM
modeled upper atmospheric profiles for the main neutral and ion species
are compared to Neutral Gas and Ion Mass Spectrometer/MAVEN data showing
that the LMD-GCM can provide a satisfactory global view of Mars' upper
atmosphere. Finally, we were able to reconstruct the expected emission
brightness intensity from the oxygen exosphere using EGM. The good
agreement with the averaged measured profiles by Imaging Ultraviolet
Spectrograph during these three periods suggests that Mars' exospheric
nonthermal component can be fully explained by the reactions of
dissociative recombination of the O$_{2}$$^{+}$ ion in Mars'
ionosphere, limiting significantly our ability to extract information
from MAVEN observations of the O exosphere on other nonthermal
processes, such as sputtering.
  doi = {10.1002/2017JE005336},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Navarro}, T. and {Forget}, F. and {Millour}, E. and {Greybush}, S.~J. and 
	{Kalnay}, E. and {Miyoshi}, T.},
  title = {{The Challenge of Atmospheric Data Assimilation on Mars}},
  journal = {Earth and Space Science},
  keywords = {Mars, atmosphere, aerosols, assimilation},
  year = 2017,
  volume = 4,
  pages = {690-722},
  abstract = {{Data assimilation is carried out for the Martian atmosphere with the
Mars Climate Sounder (MCS) retrievals of temperature, dust, and ice. It
is performed for the period Ls = 180{\deg} to Ls = 320{\deg} of Mars Year
29 with the Local Ensemble Transform Kalman Filter scheme and the
Laboratoire de Météorologie Dynamique (LMD) Mars Global
Climate Model (GCM). In order to deal with the forcings of aerosols
(dust and water ice) on atmospheric temperatures, a framework is given
for multivariate analysis. It consists of assimilating a GCM variable
with the help of another GCM variable that can be more easily related to
an observation. Despite encouraging results with this method, data
assimilation is found to be intrinsically different for Mars and more
challenging, due to the Martian atmosphere being less chaotic and
exhibiting more global features than on Earth. This is reflected in the
three main issues met when achieving various data assimilation
experiments: (1) temperature assimilation strongly forces the GCM away
from its free-running state, due to the difficulty of assimilating
global atmospheric thermal tides; (2) because of model bias,
assimilation of airborne dust is not able to reproduce the vertical
diurnal variations of dust observed by MCS, and not present in the GCM;
and (3) water ice clouds are nearly impossible to assimilate due to the
difficulty to assimilate temperature to a sufficient precision. Overall,
further improvements of Martian data assimilation would require an
assimilation that goes beyond the local scale and more realism of the
GCM, especially for aerosols and thermal tides.
  doi = {10.1002/2017EA000274},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{S{\'a}nchez-Lavega}, A. and {Lebonnois}, S. and {Imamura}, T. and 
	{Read}, P. and {Luz}, D.},
  title = {{The Atmospheric Dynamics of Venus}},
  journal = {\ssr},
  keywords = {Venus, Atmospheric dynamics},
  year = 2017,
  volume = 212,
  pages = {1541-1616},
  abstract = {{We review our current knowledge of the atmospheric dynamics of Venus
prior to the Akatsuki mission, in the altitude range from the surface to
approximately the cloud tops located at about 100 km altitude. The
three-dimensional structure of the wind field in this region has been
determined with a variety of techniques over a broad range of spatial
and temporal scales (from the mesoscale to planetary, from days to
years, in daytime and nighttime), spanning a period of about 50 years
(from the 1960s to the present). The global panorama is that the mean
atmospheric motions are essentially zonal, dominated by the so-called
super-rotation (an atmospheric rotation that is 60 to 80 times faster
than that of the planetary body). The zonal winds blow westward (in the
same direction as the planet rotation) with a nearly constant speed of
{\tilde} 100 m s\^{}$\{$-1$\}$ at the cloud tops (65-70 km altitude) from latitude
50{\deg}N to 50{\deg}S, then decreasing their speeds monotonically from
these latitudes toward the poles. Vertically, the zonal winds decrease
with decreasing altitude towards velocities {\tilde} 1-3 m s\^{}$\{$-1$\}$ in a
layer of thickness {\tilde} 10 km close to the surface. Meridional
motions with peak speeds of {\tilde} 15 m s\^{}$\{$-1$\}$ occur within the upper
cloud at 65 km altitude and are related to a Hadley cell circulation and
to the solar thermal tide. Vertical motions with speeds {\tilde}1-3 m
s\^{}$\{$-1$\}$ occur in the statically unstable layer between altitudes of
{\tilde} 50 - 55 km. All these motions are permanent with speed
variations of the order of {\tilde}10\%. Various types of wave, from
mesoscale gravity waves to Rossby-Kelvin planetary scale waves, have
been detected at and above cloud heights, and are considered to be
candidates as agents for carrying momentum that drives the
super-rotation, although numerical models do not fully reproduce all the
observed features. Momentum transport by atmospheric waves and the solar
tide is thought to be an indispensable component of the general
circulation of the Venus atmosphere. Another conspicuous feature of the
atmospheric circulation is the presence of polar vortices. These are
present in both hemispheres and are regions of warmer and lower clouds,
seen prominently at infrared wavelengths, showing a highly variable
morphology and motions. The vortices spin with a period of 2-3 days. The
South polar vortex rotates around a geographical point which is itself
displaced from the true pole of rotation by {\tilde} 3 degrees. The polar
vortex is surrounded and constrained by the cold collar, an
infrared-dark region of lower temperatures. We still lack detailed
models of the mechanisms underlying the dynamics of these features and
how they couple (or not) to the super-rotation. The nature of the
super-rotation relates to the angular momentum stored in the atmosphere
and how it is transported between the tropics and higher latitudes, and
between the deep atmosphere and upper levels. The role of eddy processes
is crucial, but likely involves the complex interaction of a variety of
different types of eddy, either forced directly by radiative heating and
mechanical interactions with the surface or through various forms of
instability. Numerical models have achieved some significant recent
success in capturing some aspects of the observed super-rotation,
consistent with the scenario discussed by Gierasch (J. Atmos. Sci.
32:1038-1044, 1975) and Rossow and Williams (J. Atmos. Sci. 36:377-389,
1979), but many uncertainties remain, especially in the deep atmosphere.
The theoretical framework developed to explain the circulation in
Venus's atmosphere is reviewed, as well as the numerical models that
have been built to elucidate the super-rotation mechanism. These tools
are used to analyze the respective roles of the different waves in the
processes driving the observed motions. Their limitations and suggested
directions for improvements are discussed.
  doi = {10.1007/s11214-017-0389-x},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Turbet}, M. and {Tran}, H.},
  title = {{Comment on ``Radiative Transfer in CO$_{2}$-Rich Atmospheres: 1. Collisional Line Mixing Implies a Colder Early Mars''}},
  journal = {Journal of Geophysical Research (Planets)},
  archiveprefix = {arXiv},
  eprint = {1711.03376},
  primaryclass = {astro-ph.EP},
  keywords = {planetary atmospheres, Mars, line mixing, CO$_{2}$, radiative transfer, spectroscopy},
  year = 2017,
  volume = 122,
  pages = {2362-2365},
  abstract = {{Ozak et al. (2016) claimed that explicitly including the effect of
CO$_{2}$ collisional line mixing in their radiative transfer
calculations yield CO$_{2}$ atmospheres that are more transparent
to infrared radiation than when spectra calculations are made using
sub-Lorentzian line shapes. This would in particular imply significantly
colder surface temperatures (up to 15 K) for early Mars than estimated
in previous studies. Here we show that the relative cooling that Ozak et
al. (2016) associated to the effect of collisional line mixing is in
fact due to a wrong choice of broadening species (air instead of
CO$_{2}$). We then calculated line-by-line spectra of pure
CO$_{2}$ atmospheres using a line-mixing model developed for
self-broadened CO$_{2}$. Using the LMD Generic model (in 1-D
radiative-convective mode), we find that calculations made with the
proper collisional line mixing model and with sub-Lorentzian line shapes
lead to differences between early Mars surface temperatures smaller than
2 K only.
  doi = {10.1002/2017JE005373},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Montmessin}, F. and {Korablev}, O. and {Lefèvre}, F. and 
	{Bertaux}, J.-L. and {Fedorova}, A. and {Trokhimovskiy}, A. and 
	{Chaufray}, J.~Y. and {Lacombe}, G. and {Reberac}, A. and {Maltagliati}, L. and 
	{Willame}, Y. and {Guslyakova}, S. and {Gérard}, J.-C. and 
	{Stiepen}, A. and {Fussen}, D. and {Mateshvili}, N. and {M{\"a}{\"a}tt{\"a}nen}, A. and 
	{Forget}, F. and {Witasse}, O. and {Leblanc}, F. and {Vandaele}, A.~C. and 
	{Marcq}, E. and {Sandel}, B. and {Gondet}, B. and {Schneider}, N. and 
	{Chaffin}, M. and {Chapron}, N.},
  title = {{SPICAM on Mars Express: A 10 year in-depth survey of the Martian atmosphere}},
  journal = {\icarus},
  year = 2017,
  volume = 297,
  pages = {195-216},
  abstract = {{The SPICAM experiment onboard Mars Express has accumulated during the
last decade a wealth of observations that has permitted a detailed
characterization of the atmospheric composition and activity from the
near-surface up to above the exosphere. The SPICAM climatology is one of
the longest assembled to date by an instrument in orbit around Mars,
offering the opportunity to study the fate of major volatile species in
the Martian atmosphere over a multi-(Mars)year timeframe. With his dual
ultraviolet (UV)-near Infrared channels, SPICAM observes spectral ranges
encompassing signatures created by a variety atmospheric gases, from
major (CO$_{2}$) to trace species (H$_{2}$O, O$_{3}$).
Here, we present a synthesis of the observations collected for water
vapor, ozone, clouds and dust, carbon dioxide, exospheric hydrogen and
airglows. The assembled climatology covers the MY 27-MY 31 period.
However, the monitoring of UV-derived species was interrupted at the end
of 2014 (MY30) due to failure of the UV channel. A SO$_{2}$
detection attempt was undertaken, but proved unsuccessful from regional
to global scales (with upper limit greater than already published ones).
One particular conclusion that stands out from this overview work
concerns the way the Martian atmosphere organizes an efficient mass
transfer between the lower and the upper atmospheric reservoirs. This
highway to space, as we name it, is best illustrated by water and
hydrogen, both species having been monitored by SPICAM in their
respective atmospheric reservoir. Coupling between the two appear to
occur on seasonal timescales, much shorter than theoretical predictions.
  doi = {10.1016/j.icarus.2017.06.022},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Rostami}, M. and {Zeitlin}, V. and {Spiga}, A.},
  title = {{On the dynamical nature of Saturn's North Polar hexagon}},
  journal = {\icarus},
  keywords = {Saturn's hexagon, Barotropic instability, Rotating shallow water model},
  year = 2017,
  volume = 297,
  pages = {59-70},
  abstract = {{An explanation of long-lived Saturn's North Polar hexagonal circumpolar
jet in terms of instability of the coupled system polar vortex -
circumpolar jet is proposed in the framework of the rotating shallow
water model, where scarcely known vertical structure of the Saturn's
atmosphere is averaged out. The absence of a hexagonal structure at
Saturn's South Pole is explained similarly. By using the latest
state-of-the-art observed winds in Saturn's polar regions a detailed
linear stability analysis of the circumpolar jet is performed (i)
excluding (``jet-only'' configuration), and (2) including (``jet + vortex''
configuration) the north polar vortex in the system. A domain of
parameters: latitude of the circumpolar jet and curvature of its
azimuthal velocity profile, where the most unstable mode of the system
has azimuthal wavenumber 6, is identified. Fully nonlinear simulations
are then performed, initialized either with the most unstable mode of
small amplitude, or with the random combination of unstable modes. It is
shown that developing barotropic instability of the ``jet+vortex'' system
produces a long-living structure akin to the observed hexagon, which is
not the case of the ``jet-only'' system, which was studied in this context
in a number of papers in literature. The north polar vortex, thus, plays
a decisive dynamical role. The influence of moist convection, which was
recently suggested to be at the origin of Saturn's North Polar vortex
system in the literature, is investigated in the framework of the model
and does not alter the conclusions.
  doi = {10.1016/j.icarus.2017.06.006},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Garcia}, R.~F. and {Brissaud}, Q. and {Rolland}, L. and {Martin}, R. and 
	{Komatitsch}, D. and {Spiga}, A. and {Lognonné}, P. and 
	{Banerdt}, B.},
  title = {{Finite-Difference Modeling of Acoustic and Gravity Wave Propagation in Mars Atmosphere: Application to Infrasounds Emitted by Meteor Impacts}},
  journal = {\ssr},
  keywords = {Mars, InSight mission, Atmosphere, Acoustic waves, Gravity waves, Impacts, Pressure sensor, Numerical modeling},
  year = 2017,
  volume = 211,
  pages = {547-570},
  abstract = {{The propagation of acoustic and gravity waves in planetary atmospheres
is strongly dependent on both wind conditions and attenuation
properties. This study presents a finite-difference modeling tool
tailored for acoustic-gravity wave applications that takes into account
the effect of background winds, attenuation phenomena (including
relaxation effects specific to carbon dioxide atmospheres) and wave
amplification by exponential density decrease with height. The
simulation tool is implemented in 2D Cartesian coordinates and first
validated by comparison with analytical solutions for benchmark
problems. It is then applied to surface explosions simulating meteor
impacts on Mars in various Martian atmospheric conditions inferred from
global climate models. The acoustic wave travel times are validated by
comparison with 2D ray tracing in a windy atmosphere. Our simulations
predict that acoustic waves generated by impacts can refract back to the
surface on wind ducts at high altitude. In addition, due to the strong
nighttime near-surface temperature gradient on Mars, the acoustic waves
are trapped in a waveguide close to the surface, which allows a
night-side detection of impacts at large distances in Mars plains. Such
theoretical predictions are directly applicable to future measurements
by the INSIGHT NASA Discovery mission.
  doi = {10.1007/s11214-016-0324-6},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Kenda}, B. and {Lognonné}, P. and {Spiga}, A. and {Kawamura}, T. and 
	{Kedar}, S. and {Banerdt}, W.~B. and {Lorenz}, R. and {Banfield}, D. and 
	{Golombek}, M.},
  title = {{Modeling of Ground Deformation and Shallow Surface Waves Generated by Martian Dust Devils and Perspectives for Near-Surface Structure Inversion}},
  journal = {\ssr},
  keywords = {Dust devils, Mars, Ground tilt, Subsurface, Large-eddy simulation, Insight},
  year = 2017,
  volume = 211,
  pages = {501-524},
  abstract = {{We investigated the possible seismic signatures of dust devils on Mars,
both at long and short period, based on the analysis of Earth data and
on forward modeling for Mars. Seismic and meteorological data collected
in the Mojave Desert, California, recorded the signals generated by dust
devils. In the 10-100 s band, the quasi-static surface deformation
triggered by pressure fluctuations resulted in detectable ground-tilt
effects: these are in good agreement with our modeling based on
Sorrells' theory. In addition, high-frequency records also exhibit a
significant excitation in correspondence to dust devil episodes. Besides
wind noise, this signal includes shallow surface waves due to the
atmosphere-surface coupling and is used for a preliminary inversion of
the near-surface S-wave profile down to 50 m depth. In the case of Mars,
we modeled the long-period signals generated by the pressure field
resulting from turbulence-resolving Large-Eddy Simulations. For typical
dust-devil-like vortices with pressure drops of a couple Pascals, the
corresponding horizontal acceleration is of a few nm/s$^{2}$ for
rocky subsurface models and reaches 10-20 nm/s$^{2}$ for weak
regolith models. In both cases, this signal can be detected by the
Very-Broad Band seismometers of the InSight/SEIS experiment up to a
distance of a few hundred meters from the vortex, the amplitude of the
signal decreasing as the inverse of the distance. Atmospheric vortices
are thus expected to be detected at the InSight landing site; the
analysis of their seismic and atmospheric signals could lead to
additional constraints on the near-surface structure, more precisely on
the ground compliance and possibly on the seismic velocities.
  doi = {10.1007/s11214-017-0378-0},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Murdoch}, N. and {Kenda}, B. and {Kawamura}, T. and {Spiga}, A. and 
	{Lognonné}, P. and {Mimoun}, D. and {Banerdt}, W.~B.},
  title = {{Estimations of the Seismic Pressure Noise on Mars Determined from Large Eddy Simulations and Demonstration of Pressure Decorrelation Techniques for the Insight Mission}},
  journal = {\ssr},
  archiveprefix = {arXiv},
  eprint = {1704.05664},
  primaryclass = {physics.geo-ph},
  keywords = {Mars, Seismology, Pressure, Atmosphere, Regolith, Geophysics},
  year = 2017,
  volume = 211,
  pages = {457-483},
  abstract = {{The atmospheric pressure fluctuations on Mars induce an elastic response
in the ground that creates a ground tilt, detectable as a seismic signal
on the InSight seismometer SEIS. The seismic pressure noise is modeled
using Large Eddy Simulations (LES) of the wind and surface pressure at
the InSight landing site and a Green's function ground deformation
approach that is subsequently validated via a detailed comparison with
two other methods: a spectral approach, and an approach based on
Sorrells' theory (Sorrells, Geophys. J. Int. 26:71-82, 1971; Sorrells et
al., Nat. Phys. Sci. 229:14-16, 1971). The horizontal accelerations as a
result of the ground tilt due to the LES turbulence-induced pressure
fluctuations are found to be typically {\tilde} 2 - 40 nm/s$^{2}$
in amplitude, whereas the direct horizontal acceleration is two orders
of magnitude smaller and is thus negligible in comparison. The vertical
accelerations are found to be {\tilde} 0.1-6 nm/s$^{2}$ in
amplitude. These are expected to be worst-case estimates for the seismic
noise as we use a half-space approximation; the presence at some
(shallow) depth of a harder layer would significantly reduce
quasi-static displacement and tilt effects.

We show that under calm conditions, a single-pressure measurement is
representative of the large-scale pressure field (to a distance of
several kilometers), particularly in the prevailing wind direction.
However, during windy conditions, small-scale turbulence results in a
reduced correlation between the pressure signals, and the
single-pressure measurement becomes less representative of the pressure
field. The correlation between the seismic signal and the pressure
signal is found to be higher for the windiest period because the seismic
pressure noise reflects the atmospheric structure close to the

In the same way that we reduce the atmospheric seismic signal by making
use of a pressure sensor that is part of the InSight Auxiliary Payload
Sensor Suite, we also the use the synthetic noise data obtained from the
LES pressure field to demonstrate a decorrelation strategy. We show that
our decorrelation approach is efficient, resulting in a reduction by a
factor of {\tilde} 5 in the observed horizontal tilt noise (in the wind
direction) and the vertical noise. This technique can, therefore, be
used to remove the pressure signal from the seismic data obtained on
Mars during the InSight mission.
  doi = {10.1007/s11214-017-0343-y},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Fletcher}, L.~N. and {Guerlet}, S. and {Orton}, G.~S. and {Cosentino}, R.~G. and 
	{Fouchet}, T. and {Irwin}, P.~G.~J. and {Li}, L. and {Flasar}, F.~M. and 
	{Gorius}, N. and {Morales-Juber{\'{\i}}as}, R.},
  title = {{Disruption of Saturn's quasi-periodic equatorial oscillation by the great northern storm}},
  journal = {Nature Astronomy},
  archiveprefix = {arXiv},
  eprint = {1803.07875},
  primaryclass = {astro-ph.EP},
  year = 2017,
  volume = 1,
  pages = {765-770},
  abstract = {{The equatorial middle atmospheres of the Earth$^{1}$,
Jupiter$^{2}$ and Saturn$^{3,4}$ all exhibit a remarkably
similar phenomenon{\mdash}a vertical, cyclic pattern of alternating
temperatures and zonal (east-west) wind regimes that propagate slowly
downwards with a well-defined multi-year period. Earth's quasi-biennial
oscillation (QBO) (observed in the lower stratospheric winds with an
cycles exhibited by our climate system$^{1,5,6}$, and yet recent
work has shown that this regularity can be disrupted by events occurring
far away from the equatorial region, an example of a phenomenon known as
atmospheric teleconnection$^{7,8}$. Here, we reveal that Saturn's
equatorial quasi-periodic oscillation (QPO) (with an  15-year
period$^{3,9}$) can also be dramatically perturbed. An intense
springtime storm erupted at Saturn's northern mid-latitudes in December
2010$^{10-12}$, spawning a gigantic hot vortex in the stratosphere
at 40{\deg} N that persisted for three years$^{13}$. Far from the
storm, the Cassini temperature measurements showed a dramatic  10 K
cooling in the 0.5-5 mbar range across the entire equatorial region,
disrupting the regular QPO pattern and significantly altering the
middle-atmospheric wind structure, suggesting an injection of westward
momentum into the equatorial wind system from waves generated by the
northern storm. Hence, as on Earth, meteorological activity at
mid-latitudes can have a profound effect on the regular atmospheric
cycles in Saturn's tropics, demonstrating that waves can provide
horizontal teleconnections between the phenomena shaping the middle
atmospheres of giant planets.
  doi = {10.1038/s41550-017-0271-5},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Turbet}, M. and {Forget}, F. and {Leconte}, J. and {Charnay}, B. and 
	{Tobie}, G.},
  title = {{CO$_{2}$ condensation is a serious limit to the deglaciation of Earth-like planets}},
  journal = {Earth and Planetary Science Letters},
  archiveprefix = {arXiv},
  eprint = {1703.04624},
  primaryclass = {astro-ph.EP},
  keywords = {climate, snowball, exoplanet, CO$_{2}$ condensation, habitability, climate cycling},
  year = 2017,
  volume = 476,
  pages = {11-21},
  abstract = {{It is widely believed that the carbonate-silicate cycle is the main
agent, through volcanism, to trigger deglaciations by CO$_{2}$
greenhouse warming on Earth and on Earth-like planets when they get in a
frozen state. Here we use a 3D Global Climate Model to simulate the
ability of planets initially completely frozen to escape from glaciation
episodes by accumulating enough gaseous CO$_{2}$. The model
includes CO$_{2}$ condensation and sublimation processes and the
water cycle. We find that planets with Earth-like characteristics (size,
mass, obliquity, rotation rate, etc.) orbiting a Sun-like star may never
be able to escape from a glaciation era, if their orbital distance is
greater than {\sim}1.27 Astronomical Units (Flux $\lt$ 847 
Wm$^{-2}$ or 62\% of the Solar constant), because CO$_{2}$
would condense at the poles - here the cold traps - forming permanent
CO$_{2}$ ice caps. This limits the amount of CO$_{2}$ in the
atmosphere and thus its greenhouse effect. Furthermore, our results
indicate that for (1) high rotation rates (P$_{rot}$ $\lt$ 24  h),
(2) low obliquity (obliquity $\lt$23.5{\deg}), (3) low background gas
partial pressures ($\lt$1 bar), and (4) high water ice albedo
(H$_{2}$O albedo $\gt$ 0.6), this critical limit could occur at a
significantly lower equivalent distance (or higher insolation). For each
possible configuration, we show that the amount of CO$_{2}$ that
can be trapped in the polar caps depends on the efficiency of
CO$_{2}$ ice to flow laterally as well as its gravitational
stability relative to subsurface water ice. We find that a frozen
Earth-like planet located at 1.30 AU of a Sun-like star could store as
much as 1.5, 4.5 and 15 bars of dry ice at the poles, for internal heat
fluxes of 100, 30 and 10 mW m$^{-2}$, respectively. But these
amounts are in fact lower limits. For planets with a significant water
ice cover, we show that CO$_{2}$ ice deposits should be
gravitationally unstable. They get buried beneath the water ice cover in
geologically short timescales of {\sim}10$^{4}$ yrs, mainly
controlled by the viscosity of water ice. CO$_{2}$ would be
permanently sequestered underneath the water ice cover, in the form of
CO$_{2}$ liquids, CO$_{2}$ clathrate hydrates and/or
dissolved in subglacial water reservoirs (if any). This would
considerably increase the amount of CO$_{2}$ trapped and further
reduce the probability of deglaciation.
  doi = {10.1016/j.epsl.2017.07.050},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Spiga}, A. and {Hinson}, D.~P. and {Madeleine}, J.-B. and {Navarro}, T. and 
	{Millour}, E. and {Forget}, F. and {Montmessin}, F.},
  title = {{Snow precipitation on Mars driven by cloud-induced night-time convection}},
  journal = {Nature Geoscience},
  year = 2017,
  volume = 10,
  pages = {652-657},
  abstract = {{Although it contains less water vapour than Earth's atmosphere, the
Martian atmosphere hosts clouds. These clouds, composed of water-ice
particles, influence the global transport of water vapour and the
seasonal variations of ice deposits. However, the influence of water-ice
clouds on local weather is unclear: it is thought that Martian clouds
are devoid of moist convective motions, and snow precipitation occurs
only by the slow sedimentation of individual particles. Here we present
numerical simulations of the meteorology in Martian cloudy regions that
demonstrate that localized convective snowstorms can occur on Mars. We
show that such snowstorms--or ice microbursts--can explain deep
night-time mixing layers detected from orbit and precipitation
signatures detected below water-ice clouds by the Phoenix lander. In our
simulations, convective snowstorms occur only during the Martian night,
and result from atmospheric instability due to radiative cooling of
water-ice cloud particles. This triggers strong convective plumes within
and below clouds, with fast snow precipitation resulting from the
vigorous descending currents. Night-time convection in Martian water-ice
clouds and the associated snow precipitation lead to transport of water
both above and below the mixing layers, and thus would affect Mars'
water cycle past and present, especially under the high-obliquity
conditions associated with a more intense water cycle.
  doi = {10.1038/ngeo3008},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Limaye}, S.~S. and {Lebonnois}, S. and {Mahieux}, A. and {P{\"a}tzold}, M. and 
	{Bougher}, S. and {Bruinsma}, S. and {Chamberlain}, S. and {Clancy}, R.~T. and 
	{Gérard}, J.-C. and {Gilli}, G. and {Grassi}, D. and {Haus}, R. and 
	{Herrmann}, M. and {Imamura}, T. and {Kohler}, E. and {Krause}, P. and 
	{Migliorini}, A. and {Montmessin}, F. and {Pere}, C. and {Persson}, M. and 
	{Piccialli}, A. and {Rengel}, M. and {Rodin}, A. and {Sandor}, B. and 
	{Sornig}, M. and {Svedhem}, H. and {Tellmann}, S. and {Tanga}, P. and 
	{Vandaele}, A.~C. and {Widemann}, T. and {Wilson}, C.~F. and 
	{M{\"u}ller-Wodarg}, I. and {Zasova}, L.},
  title = {{The thermal structure of the Venus atmosphere: Intercomparison of Venus Express and ground based observations of vertical temperature and density profiles$^{✰}$}},
  journal = {\icarus},
  year = 2017,
  volume = 294,
  pages = {124-155},
  abstract = {{The Venus International Reference Atmosphere (VIRA) model contains
tabulated values of temperature and number densities obtained by the
experiments on the Venera entry probes, Pioneer Venus Orbiter and
multi-probe missions in the 1980s. The instruments on the recent Venus
Express orbiter mission generated a significant amount of new
observational data on the vertical and horizontal structure of the Venus
atmosphere from 40 km to about 180 km altitude from April 2006 to
November 2014. Many ground based experiments have provided data on the
upper atmosphere (90-130 km) temperature structure since the publication
of VIRA in 1985. The ``Thermal Structure of the Venus Atmosphere'' Team
was supported by the International Space Studies Institute (ISSI), Bern,
Switzerland, from 2013 to 2015 in order to combine and compare the
ground-based observations and the VEx observations of the thermal
structure as a first step towards generating an updated VIRA model.
Results of this comparison are presented in five latitude bins and three
local time bins by assuming hemispheric symmetry. The intercomparison of
the ground-based and VEx results provides for the first time a
consistent picture of the temperature and density structure in the 40
km-180 km altitude range. The Venus Express observations have
considerably increased our knowledge of the Venus atmospheric thermal
structure above {\sim}40 km and provided new information above 100 km.
There are, however, still observational gaps in latitude and local time
above certain regions. Considerable variability in the temperatures and
densities is seen above 100 km but certain features appear to be
systematically present, such as a succession of warm and cool layers.
Preliminary modeling studies support the existence of such layers in
agreement with a global scale circulation. The intercomparison focuses
on average profiles but some VEx experiments provide sufficient global
coverage to identify solar thermal tidal components.
  doi = {10.1016/j.icarus.2017.04.020},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Charnay}, B. and {Le Hir}, G. and {Fluteau}, F. and {Forget}, F. and 
	{Catling}, D.~C.},
  title = {{A warm or a cold early Earth? New insights from a 3-D climate-carbon model}},
  journal = {Earth and Planetary Science Letters},
  archiveprefix = {arXiv},
  eprint = {1706.06842},
  primaryclass = {astro-ph.EP},
  keywords = {early Earth, climate, carbon cycle, Hadean, Archean, Late Heavy Bombardment},
  year = 2017,
  volume = 474,
  pages = {97-109},
  abstract = {{Oxygen isotopes in marine cherts have been used to infer hot oceans
during the Archean with temperatures between 60 {\deg}C (333 K) and 80
{\deg}C (353 K). Such climates are challenging for the early Earth warmed
by the faint young Sun. The interpretation of the data has therefore
been controversial. 1D climate modeling inferred that such hot climates
would require very high levels of CO$_{2}$ (2-6 bars). Previous
carbon cycle modeling concluded that such stable hot climates were
impossible and that the carbon cycle should lead to cold climates during
the Hadean and the Archean. Here, we revisit the climate and carbon
cycle of the early Earth at 3.8 Ga using a 3D climate-carbon model. We
find that CO$_{2}$ partial pressures of around 1 bar could have
produced hot climates given a low land fraction and cloud feedback
effects. However, such high CO$_{2}$ partial pressures should not
have been stable because of the weathering of terrestrial and oceanic
basalts, producing an efficient stabilizing feedback. Moreover, the
weathering of impact ejecta during the Late Heavy Bombardment (LHB)
would have strongly reduced the CO$_{2}$ partial pressure leading
to cold climates and potentially snowball Earth events after large
impacts. Our results therefore favor cold or temperate climates with
global mean temperatures between around 8 {\deg}C (281 K) and 30 {\deg}C
(303 K) and with 0.1-0.36 bar of CO$_{2}$ for the late Hadean and
early Archean. Finally, our model suggests that the carbon cycle was
efficient for preserving clement conditions on the early Earth without
necessarily requiring any other greenhouse gas or warming process.
  doi = {10.1016/j.epsl.2017.06.029},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lebonnois}, S. and {Schubert}, G.},
  title = {{The deep atmosphere of Venus and the possible role of density-driven separation of CO$_{2}$ and N$_{2}$}},
  journal = {Nature Geoscience},
  year = 2017,
  volume = 10,
  pages = {473-477},
  abstract = {{With temperatures around 700 K and pressures of around 75 bar, the
deepest 12 km of the atmosphere of Venus are so hot and dense that the
atmosphere behaves like a supercritical fluid. The Soviet VeGa-2 probe
descended through the atmosphere in 1985 and obtained the only reliable
temperature profile for the deep Venusian atmosphere thus far. In this
temperature profile, the atmosphere appears to be highly unstable at
altitudes below 7 km, contrary to expectations. We argue that the VeGa-2
temperature profile could be explained by a change in the atmospheric
gas composition, and thus molecular mass, with depth. We propose that
the deep atmosphere consists of a non-homogeneous layer in which the
abundance of N$_{2}$--the second most abundant constituent of the
Venusian atmosphere after CO$_{2}$--gradually decreases to
near-zero at the surface. It is difficult to explain a decline in
N$_{2}$ towards the surface with known nitrogen sources and sinks
for Venus. Instead we suggest, partly based on experiments on
supercritical fluids, that density-driven separation of N$_{2}$
from CO$_{2}$ can occur under the high pressures of Venus's deep
atmosphere, possibly by molecular diffusion, or by natural
density-driven convection. If so, the amount of nitrogen in the
atmosphere of Venus is 15\% lower than commonly assumed. We suggest that
similar density-driven separation could occur in other massive planetary
  doi = {10.1038/ngeo2971},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Pottier}, A. and {Forget}, F. and {Montmessin}, F. and {Navarro}, T. and 
	{Spiga}, A. and {Millour}, E. and {Szantai}, A. and {Madeleine}, J.-B.
  title = {{Unraveling the martian water cycle with high-resolution global climate simulations}},
  journal = {\icarus},
  keywords = {Mars atmosphere, Atmospheres dynamics, Mars, Climate, Meteorology},
  year = 2017,
  volume = 291,
  pages = {82-106},
  abstract = {{Global climate modeling of the Mars water cycle is usually performed at
relatively coarse resolution (200 - 300km), which may not be sufficient
to properly represent the impact of waves, fronts, topography effects on
the detailed structure of clouds and surface ice deposits. Here, we
present new numerical simulations of the annual water cycle performed at
a resolution of 1{\deg} {\times} 1{\deg} ({\sim} 60 km in latitude). The
model includes the radiative effects of clouds, whose influence on the
thermal structure and atmospheric dynamics is significant, thus we also
examine simulations with inactive clouds to distinguish the direct
impact of resolution on circulation and winds from the indirect impact
of resolution via water ice clouds. To first order, we find that the
high resolution does not dramatically change the behavior of the system,
and that simulations performed at {\sim} 200 km resolution capture well
the behavior of the simulated water cycle and Mars climate.
Nevertheless, a detailed comparison between high and low resolution
simulations, with reference to observations, reveal several significant
changes that impact our understanding of the water cycle active today on
Mars. The key northern cap edge dynamics are affected by an increase in
baroclinic wave strength, with a complication of northern summer
dynamics. South polar frost deposition is modified, with a westward
longitudinal shift, since southern dynamics are also influenced.
Baroclinic wave mode transitions are observed. New transient phenomena
appear, like spiral and streak clouds, already documented in the
observations. Atmospheric circulation cells in the polar region exhibit
a large variability and are fine structured, with slope winds. Most
modeled phenomena affected by high resolution give a picture of a more
turbulent planet, inducing further variability. This is challenging for
long-period climate studies.
  doi = {10.1016/j.icarus.2017.02.016},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Vago}, J.~L. and {Westall}, F. and {Pasteur Instrument Team} and 
	{Pasteur Landing Team} and {Coates}, A.~J. and {Jaumann}, R. and 
	{Korablev}, O. and {Ciarletti}, V. and {Mitrofanov}, I. and 
	{Josset}, J.-L. and {De Sanctis}, M.~C. and {Bibring}, J.-P. and 
	{Rull}, F. and {Goesmann}, F. and {Steininger}, H. and {Goetz}, W. and 
	{Brinckerhoff}, W. and {Szopa}, C. and {Raulin}, F. and {Westall}, F. and 
	{Edwards}, H.~G.~M. and {Whyte}, L.~G. and {Fairén}, A.~G. and 
	{Bibring}, J.-P. and {Bridges}, J. and {Hauber}, E. and {Ori}, G.~G. and 
	{Werner}, S. and {Loizeau}, D. and {Kuzmin}, R.~O. and {Williams}, R.~M.~E. and 
	{Flahaut}, J. and {Forget}, F. and {Vago}, J.~L. and {Rodionov}, D. and 
	{Korablev}, O. and {Svedhem}, H. and {Sefton-Nash}, E. and {Kminek}, G. and 
	{Lorenzoni}, L. and {Joudrier}, L. and {Mikhailov}, V. and {Zashchirinskiy}, A. and 
	{Alexashkin}, S. and {Calantropio}, F. and {Merlo}, A. and {Poulakis}, P. and 
	{Witasse}, O. and {Bayle}, O. and {Bay{\'o}n}, S. and {Meierhenrich}, U. and 
	{Carter}, J. and {Garc{\'{\i}}a-Ruiz}, J.~M. and {Baglioni}, P. and 
	{Haldemann}, A. and {Ball}, A.~J. and {Debus}, A. and {Lindner}, R. and 
	{Haessig}, F. and {Monteiro}, D. and {Trautner}, R. and {Voland}, C. and 
	{Rebeyre}, P. and {Goulty}, D. and {Didot}, F. and {Durrant}, S. and 
	{Zekri}, E. and {Koschny}, D. and {Toni}, A. and {Visentin}, G. and 
	{Zwick}, M. and {van Winnendael}, M. and {Azkarate}, M. and 
	{Carreau}, C. and {ExoMars Project Team}},
  title = {{Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover}},
  journal = {Astrobiology},
  keywords = {Biosignatures, ExoMars, Landing sites, Mars rover, Search for life},
  year = 2017,
  volume = 17,
  pages = {471-510},
  abstract = {{The second ExoMars mission will be launched in 2020 to target an ancient
location interpreted to have strong potential for past habitability and
for preserving physical and chemical biosignatures (as well as
abiotic/prebiotic organics). The mission will deliver a lander with
instruments for atmospheric and geophysical investigations and a rover
tasked with searching for signs of extinct life. The ExoMars rover will
be equipped with a drill to collect material from outcrops and at depth
down to 2 m. This subsurface sampling capability will provide the best
chance yet to gain access to chemical biosignatures. Using the powerful
Pasteur payload instruments, the ExoMars science team will conduct a
holistic search for traces of life and seek corroborating geological
context information.
  doi = {10.1089/ast.2016.1533},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Luger}, R. and {Sestovic}, M. and {Kruse}, E. and {Grimm}, S.~L. and 
	{Demory}, B.-O. and {Agol}, E. and {Bolmont}, E. and {Fabrycky}, D. and 
	{Fernandes}, C.~S. and {Van Grootel}, V. and {Burgasser}, A. and 
	{Gillon}, M. and {Ingalls}, J.~G. and {Jehin}, E. and {Raymond}, S.~N. and 
	{Selsis}, F. and {Triaud}, A.~H.~M.~J. and {Barclay}, T. and 
	{Barentsen}, G. and {Howell}, S.~B. and {Delrez}, L. and {de Wit}, J. and 
	{Foreman-Mackey}, D. and {Holdsworth}, D.~L. and {Leconte}, J. and 
	{Lederer}, S. and {Turbet}, M. and {Almleaky}, Y. and {Benkhaldoun}, Z. and 
	{Magain}, P. and {Morris}, B.~M. and {Heng}, K. and {Queloz}, D.
  title = {{A seven-planet resonant chain in TRAPPIST-1}},
  journal = {Nature Astronomy},
  archiveprefix = {arXiv},
  eprint = {1703.04166},
  primaryclass = {astro-ph.EP},
  year = 2017,
  volume = 1,
  eid = {0129},
  pages = {0129},
  abstract = {{The TRAPPIST-1 system is the first transiting planet system found
orbiting an ultracool dwarf star$^{ 1 }$. At least seven planets
similar in radius to Earth were previously found to transit this host
star$^{ 2 }$. Subsequently, TRAPPIST-1 was observed as part of the
K2 mission and, with these new data, we report the measurement of an
18.77 day orbital period for the outermost transiting planet, TRAPPIST-1
h, which was previously unconstrained. This value matches our
theoretical expectations based on Laplace relations$^{ 3 }$ and
places TRAPPIST-1 h as the seventh member of a complex chain, with
three-body resonances linking every member. We find that TRAPPIST-1 h
has a radius of 0.752 R $_{⊕}$ and an equilibrium
temperature of 173{\thinsp}K. We have also measured the rotational period
of the star to be 3.3 days and detected a number of flares consistent
with a low-activity, middle-aged, late M dwarf.
  doi = {10.1038/s41550-017-0129},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Steele}, L.~J. and {Balme}, M.~R. and {Lewis}, S.~R. and {Spiga}, A.
  title = {{The water cycle and regolith-atmosphere interaction at Gale crater, Mars}},
  journal = {\icarus},
  keywords = {Mars, atmosphere, climate, surface},
  year = 2017,
  volume = 289,
  pages = {56-79},
  abstract = {{We perform mesoscale simulations of the water cycle in a region around
Gale crater, including the diffusion of water vapour in and out of the
regolith, and compare our results with measurements from the REMS
instrument on board the Curiosity rover. Simulations are performed at
three times of year, and show that diffusion in and out of the regolith
and adsorption/desorption needs to be taken into account in order to
match the diurnal variation of relative humidity measured by REMS.
During the evening and night, local downslope flows transport water
vapour down the walls of Gale crater. When including regolith-atmosphere
interaction, the amount of vapour reaching the crater floor is reduced
(by factors of 2-3 depending on season) due to vapour diffusing into the
regolith along the crater walls. The transport of vapour into Gale
crater is also affected by the regional katabatic flow over the
dichotomy boundary, with the largest flux of vapour into the regolith
initially occurring on the northern crater wall, and moving to the
southern wall by early morning. Upslope winds during the day transport
vapour desorbing and mixing out of the regolith up crater walls, where
it can then be transported a few hundred metres into the atmosphere at
convergence boundaries. Regolith-atmosphere interaction limits the
formation of surface ice by reducing water vapour abundances in the
lower atmosphere, though in some seasons ice can still form in the early
morning on eastern crater walls. Subsurface ice amounts are small in all
seasons, with ice only existing in the upper few millimetres of regolith
during the night. The results at Gale crater are representative of the
behaviour at other craters in the mesoscale domain.
  doi = {10.1016/j.icarus.2017.02.010},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Stiepen}, A. and {Jain}, S.~K. and {Schneider}, N.~M. and {Deighan}, J.~I. and 
	{Gonz{\'a}lez-Galindo}, F. and {Gérard}, J.-C. and {Milby}, Z. and 
	{Stevens}, M.~H. and {Bougher}, S. and {Evans}, J.~S. and {Stewart}, A.~I.~F. and 
	{Chaffin}, M.~S. and {Crismani}, M. and {McClintock}, W.~E. and 
	{Clarke}, J.~T. and {Holsclaw}, G.~M. and {Montmessin}, F. and 
	{Lefèvre}, F. and {Forget}, F. and {Lo}, D.~Y. and {Hubert}, B. and 
	{Jakosky}, B.~M.},
  title = {{Nitric oxide nightglow and Martian mesospheric circulation from MAVEN/IUVS observations and LMD-MGCM predictions}},
  journal = {Journal of Geophysical Research (Space Physics)},
  keywords = {Mars, airglow, mesosphere, nitric oxide, dynamics},
  year = 2017,
  volume = 122,
  pages = {5782-5797},
  abstract = {{We report results from a study of nitric oxide nightglow over the
northern hemisphere of Mars during winter, the southern hemisphere
during fall equinox, and equatorial latitudes during summer in the
northern hemisphere based on observations of the {$\delta$} and {$\gamma$}
bands between 190 and 270 nm by the Imaging UltraViolet Spectrograph
(IUVS) on the Mars Atmosphere and Volatile EvolutioN mission (MAVEN)
spacecraft. The emission reveals recombination of N and O atoms
dissociated on the dayside of Mars and transported to the nightside. We
characterize the brightness (from 0.2 to 30 kR) and altitude (from 40 to
115 km) of the NO nightglow layer, as well as its topside scale height
(mean of 11 km). We show the possible impact of atmospheric waves
forcing longitudinal variability, associated with an increased
brightness by a factor of 3 in the 140-200{\deg} longitude region in the
northern hemisphere winter and in the -102{\deg} to -48{\deg} longitude
region at summer. Such impact to the NO nightglow at Mars was not seen
before. Quantitative comparison with calculations of the LMD-MGCM
(Laboratoire de Météorologie Dynamique-Mars Global Climate
Model) suggests that the model globally reproduces the trends of the NO
nightglow emission and its seasonal variation and also indicates large
discrepancies (up to a factor 50 fainter in the model) in northern
winter at low to middle latitudes. This suggests that the predicted
transport is too efficient toward the night winter pole in the
thermosphere by {\tilde}20{\deg} latitude north.
  doi = {10.1002/2016JA023523},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Turbet}, M. and {Forget}, F. and {Head}, J.~W. and {Wordsworth}, R.
  title = {{3D modelling of the climatic impact of outflow channel formation events on early Mars}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1701.07886},
  primaryclass = {astro-ph.EP},
  year = 2017,
  volume = 288,
  pages = {10-36},
  abstract = {{Mars was characterized by cataclysmic groundwater-sourced surface
flooding that formed large outflow channels and that may have altered
the climate for extensive periods during the Hesperian era. In
particular, it has been speculated that such events could have induced
significant rainfall and caused the formation of late-stage valley
networks. We present the results of 3-D Global Climate Model simulations
reproducing the short and long term climatic impact of a wide range of
outflow channel formation events under cold ancient Mars conditions. We
find that the most intense of these events (volumes of water up to
10$^{7}$ km$^{3}$ and released at temperatures up to 320 K)
cannot trigger long-term greenhouse global warming, regardless of how
favorable are the external conditions (e.g. obliquity and seasons).
Furthermore, the intensity of the response of the events is
significantly affected by the atmospheric pressure, a parameter not well
constrained for the Hesperian era. Thin atmospheres (P $\lt$ 80 mbar) can
be heated efficiently because of their low volumetric heat capacity,
triggering the formation of a convective plume that is very efficient in
transporting water vapor and ice at the global scale. Thick atmospheres
(P $\gt$ 0.5 bar) have difficulty in producing precipitation far from the
water flow area, and are more efficient in generating snowmelt. In any
case, outflow channel formation events at any atmospheric pressure are
unable to produce rainfall or significant snowmelt at latitudes below
40{\deg}N. As an example, for an outflow channel event (under a 0.2 bar
atmospheric pressure and 45{\deg} obliquity) releasing 10$^{6}$
km$^{3}$ of water heated at 300 K and at a discharge rate of
10$^{9}$ m$^{3}$ s-$^{1}$ , the flow of water reaches
the lowest point of the northern lowlands (around {\sim}70{\deg}N,
30{\deg}W) after {\sim}3 days and forms a 200 m deep lake of 4.2 {\times}
10$^{6}$ km$^{2}$ after {\sim}20 days; the lake becomes
entirely covered by an ice layer after {\sim}500 days. Over the short
term, such an event leaves 6.5 {\times} 10$^{3}$ km$^{3}$ of
ice deposits by precipitation (0.65\% of the initial outflow volume) and
can be responsible for the melting of {\sim}80 km$^{3}$ (0.008\% of
the initial outflow volume; 1\% of the deposited precipitation).
Furthermore, these quantities decrease drastically (faster than
linearly) for lower volumes of released water. Over the long term, we
find that the presence of the ice-covered lake has a climatic impact
similar to a simple body of water ice located in the Northern Plains.

For an obliquity of {\sim}45{\deg} and atmospheric pressures $\gt$ 80 mbar,
we find that the lake ice is transported progressively southward through
the mechanisms of sublimation and adiabatic cooling. At the same time,
and as long as the initial water reservoir is not entirely sublimated (a
lifetime of 10$^{5}$ martian years for the outflow channel event
described above), ice deposits remain in the West Echus Chasma Plateau
region where hints of hydrological activity contemporaneous with outflow
channel formation events have been observed. However, because the high
albedo of ice drives Mars to even colder temperatures, snowmelt produced
by seasonal solar forcing is difficult to attain.
  doi = {10.1016/j.icarus.2017.01.024},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{White}, O.~L. and {Moore}, J.~M. and {McKinnon}, W.~B. and 
	{Spencer}, J.~R. and {Howard}, A.~D. and {Schenk}, P.~M. and 
	{Beyer}, R.~A. and {Nimmo}, F. and {Singer}, K.~N. and {Umurhan}, O.~M. and 
	{Stern}, S.~A. and {Ennico}, K. and {Olkin}, C.~B. and {Weaver}, H.~A. and 
	{Young}, L.~A. and {Cheng}, A.~F. and {Bertrand}, T. and {Binzel}, R.~P. and 
	{Earle}, A.~M. and {Grundy}, W.~M. and {Lauer}, T.~R. and {Protopapa}, S. and 
	{Robbins}, S.~J. and {Schmitt}, B. and {New Horizons Science Team}
  title = {{Geological mapping of Sputnik Planitia on Pluto}},
  journal = {\icarus},
  keywords = {Pluto, surface, Geological processes, Ices},
  year = 2017,
  volume = 287,
  pages = {261-286},
  abstract = {{The geology and stratigraphy of the feature on Pluto informally named
Sputnik Planitia is documented through geologic mapping at 1:2,000,000
scale. All units that have been mapped are presently being affected to
some degree by the action of flowing N$_{2}$ ice. The
N$_{2}$ ice plains of Sputnik Planitia display no impact craters,
and are undergoing constant resurfacing via convection, glacial flow and
sublimation. Condensation of atmospheric N$_{2}$ onto the surface
to form a bright mantle has occurred across broad swathes of Sputnik
Planitia, and appears to be partly controlled by Pluto's obliquity
cycles. The action of N$_{2}$ ice has been instrumental in
affecting uplands terrain surrounding Sputnik Planitia, and has played a
key role in the disruption of Sputnik Planitia's western margin to form
chains of blocky mountain ranges, as well in the extensive erosion by
glacial flow of the uplands to the east of Sputnik Planitia.
  doi = {10.1016/j.icarus.2017.01.011},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Bertrand}, T. and {Forget}, F.},
  title = {{3D modeling of organic haze in Pluto's atmosphere}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1702.03783},
  primaryclass = {astro-ph.EP},
  keywords = {Pluto, Atmosphere, Haze, Modeling, GCM},
  year = 2017,
  volume = 287,
  pages = {72-86},
  abstract = {{The New Horizons spacecraft, which flew by Pluto on July 14, 2015,
revealed the presence of haze in Pluto's atmosphere that were formed by
CH$_{4}$/N$_{2}$ photochemistry at high altitudes in Pluto's
atmosphere, as on Titan and Triton. In order to help the analysis of the
observations and further investigate the formation of organic haze and
its evolution at global scales, we have implemented a simple
parameterization of the formation of organic haze in our Pluto General
Circulation Model. The production of haze in our model is based on the
different steps of aerosol formation as understood on Titan and Triton:
photolysis of CH$_{4}$ in the upper atmosphere by Lyman-{$\alpha$} UV
radiation, production of various gaseous species, and conversion into
solid particles through accumulation and aggregation processes. The
simulations use properties of aerosols similar to those observed in the
detached haze layer on Titan. We compared two reference simulations ran
with a particle radius of 50  nm: with, and without South Pole
N$_{2}$ condensation. We discuss the impact of the particle radius
and the lifetime of the precursors on the haze distribution. We simulate
CH$_{4}$ photolysis and the haze formation up to 600  km above the
surface. Results show that CH$_{4}$ photolysis in Pluto's
atmosphere in 2015 occurred mostly in the sunlit summer hemisphere with
a peak at an altitude of 250  km, though the interplanetary source of
Lyman-{$\alpha$} flux can induce some photolysis even in the Winter
hemisphere. We obtained an extensive haze up to altitudes comparable
with the observations, and with non-negligible densities up to 500  km
altitude. In both reference simulations, the haze density is not
strongly impacted by the meridional circulation. With No South Pole
N$_{2}$ condensation, the maximum nadir opacity and haze extent is
obtained at the North Pole. With South Pole N$_{2}$ condensation,
the descending parcel of air above the South Pole leads to a
latitudinally more homogeneous haze density with a slight density peak
at the South Pole. The visible opacities obtained from the computed mass
of haze, which is about 2-4 {\times}10$^{-7}$ g cm-$^{2}$ in
the summer hemisphere, are similar for most of the simulation cases and
in the range of 0.001-0.01, which is consistent with recent observations
of Pluto and their interpretation.
  doi = {10.1016/j.icarus.2017.01.016},
  adsurl = {},
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  author = {{Forget}, F. and {Bertrand}, T. and {Vangvichith}, M. and {Leconte}, J. and 
	{Millour}, E. and {Lellouch}, E.},
  title = {{A post-new horizons global climate model of Pluto including the N$_{2}$, CH$_{4}$ and CO cycles}},
  journal = {\icarus},
  keywords = {Pluto, Pluto, atmosphere, Atmospheres, composition, Atmospheres, dynamics},
  year = 2017,
  volume = 287,
  pages = {54-71},
  abstract = {{We have built a new 3D Global Climate Model (GCM) to simulate Pluto as
observed by New Horizons in 2015. All key processes are parametrized on
the basis of theoretical equations, including atmospheric dynamics and
transport, turbulence, radiative transfer, molecular conduction, as well
as phases changes for N$_{2}$, CH$_{2}$ and CO. Pluto's
climate and ice cycles are found to be very sensitive to model
parameters and initial states. Nevertheless, a reference simulation is
designed by running a fast, reduced version of the GCM with simplified
atmospheric transport for 40,000 Earth years to initialize the surface
ice distribution and sub-surface temperatures, from which a
28-Earth-year full GCM simulation is performed. Assuming a topographic
depression in a Sputnik-planum (SP)-like crater on the anti-Charon
hemisphere, a realistic Pluto is obtained, with most N$_{2}$ and
CO ices accumulated in the crater, methane frost covering both
hemispheres except for the equatorial regions, and a surface pressure
near 1.1 Pa in 2015 with an increase between 1988 and 2015, as reported
from stellar occultations. Temperature profiles are in qualitative
agreement with the observations. In particular, a cold atmospheric layer
is obtained in the lowest kilometers above Sputnik Planum, as observed
by New Horizons's REX experiment. It is shown to result from the
combined effect of the topographic depression and N$_{2}$ daytime
sublimation. In the reference simulation with surface N$_{2}$ ice
exclusively present in Sputnik Planum, the global circulation is only
forced by radiative heating gradients and remains relatively weak.
Surface winds are locally induced by topography slopes and by
N$_{2}$ condensation and sublimation around Sputnik Planum.
However, the circulation can be more intense depending on the exact
distribution of surface N$_{2}$ frost. This is illustrated in an
alternative simulation with N$_{2}$ condensing in the South Polar
regions and N$_{2}$ frost covering latitudes between 35{\deg}N and
48{\deg}N. A global condensation flow is then created, inducing strong
surface winds everywhere, a prograde jet in the southern high latitudes,
and an equatorial superrotation likely forced by barotropic
instabilities in the southern jet. Using realistic parameters, the GCM
predict atmospheric concentrations of CO and CH$_{4}$ in good
agreement with the observations. N$_{2}$ and CO do not condense in
the atmosphere, but CH$_{4}$ ice clouds can form during daytime at
low altitude near the regions covered by N$_{2}$ ice (assuming
that nucleation is efficient enough). This global climate model can be
used to study many aspects of the Pluto environment. For instance,
organic hazes are included in the GCM and analysed in a companion paper
(Bertrand and Forget, Icarus, this issue).
  doi = {10.1016/j.icarus.2016.11.038},
  adsurl = {},
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  author = {{Mendillo}, M. and {Narvaez}, C. and {Vogt}, M.~F. and {Mayyasi}, M. and 
	{Mahaffy}, P. and {Benna}, M. and {Andersson}, L. and {Campbell}, B. and 
	{N{\v e}mec}, F. and {Ma}, Y.~J. and {Chaufray}, J.-Y. and {Leblanc}, F. and 
	{Gonzalez-Galindo}, F. and {Lopez-Valverde}, M.~{\'A}. and {Forget}, F. and 
	{Jakosky}, B.},
  title = {{MAVEN and the total electron content of the Martian ionosphere}},
  journal = {Journal of Geophysical Research (Space Physics)},
  keywords = {total electron content, Mars, MAVEN, ionosphere},
  year = 2017,
  volume = 122,
  pages = {3526-3537},
  abstract = {{Model studies of the ionosphere of Mars under daytime conditions reveal
that for solar zenith angles of 0{\deg}-40{\deg}, the shapes and
magnitudes of the electron density profiles N$_{e}$(h) change by
only small amounts. This suggests that midday observations made by MAVEN
instruments along slanted orbit segments can be used to represent
vertical profiles. The total electron content (TEC), defined as the
height integral of N$_{e}$(h), is a measure of the cold plasma
reservoir of the Martian ionosphere. During MAVEN's Deep-Dip-\#2 campaign
of April 2015, observations of total ion density by Neutral Gas and Ion
Mass Spectrometer and electron density by Langmuir Probe and Waves from
periapse ( 130 km) to 400 km were used to form
$\lt$TEC$\gt$$_{topside}${\mdash}validated by independent diagnostics
and models. Orbit-by-orbit changes in topside TEC were then used to
assess the magnitudes of plasma escape associated with both large and
small changes in the topside slope of N$_{e}$(h){\mdash}called an
``ionopause episode.'' The TEC changes due to these episodes, generalized
to a global change, resulted in an escape flux of  3-6 {\times}
10$^{24}$ ions/s, an escape rate consistent with prior observation
by Phobos-2, Mars Express, and MAVEN's own in situ studies.
  doi = {10.1002/2016JA023474},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  title = {{Introduction}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {xiii},
  doi = {10.1017/9781139060172.001},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  title = {{Future Prospects}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {526-568},
  doi = {10.1017/9781139060172.018},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Forget}, F. and {Byrne}, S. and {Head}, J.~W. and {Mischna}, M.~A. and 
	{Sch{\"o}rghofer}, N.},
  title = {{Recent Climate Variations}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {464-496},
  doi = {10.1017/9781139060172.016},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Titus}, T.~N. and {Byrne}, S. and {Colaprete}, A. and {Forget}, F. and 
	{Michaels}, T.~I. and {Prettyman}, T.~H.},
  title = {{The CO2 Cycle}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {338-373},
  doi = {10.1017/9781139060172.012},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Rafkin}, S.~C.~R. and {Spiga}, A. and {Michaels}, T.~I.},
  title = {{Mesoscale Meteorology}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {172-202},
  doi = {10.1017/9781139060172.008},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Read}, P.~L. and {Galperin}, B. and {Larsen}, S.~E. and {Lewis}, S.~R. and 
	{M{\"a}{\"a}tt{\"a}nen}, A. and {Petrosyan}, A. and {Renn{\'o}}, N. and 
	{Savij{\"a}rvi}, H. and {Siili}, T. and {Spiga}, A. and {Toigo}, A. and 
	{V{\'a}zquez}, L.},
  title = {{The Martian Planetary Boundary Layer}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {106-171},
  doi = {10.1017/9781139060172.007},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Smith}, M.~D. and {Bougher}, S.~W. and {Encrenaz}, T. and {Forget}, F. and 
	{Kleinb{\"o}hl}, A.},
  title = {{Thermal Structure and Composition}},
  journal = {Asteroids, Comets, Meteors - ACM2017},
  year = 2017,
  editor = {{Haberle}, R.~M. and {Clancy}, R.~T. and {Forget}, F. and {Smith}, M.~D. and 
	{Zurek}, R.~W.},
  pages = {20-41},
  doi = {10.1017/9781139060172.004},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Gillon}, M. and {Triaud}, A.~H.~M.~J. and {Demory}, B.-O. and 
	{Jehin}, E. and {Agol}, E. and {Deck}, K.~M. and {Lederer}, S.~M. and 
	{de Wit}, J. and {Burdanov}, A. and {Ingalls}, J.~G. and {Bolmont}, E. and 
	{Leconte}, J. and {Raymond}, S.~N. and {Selsis}, F. and {Turbet}, M. and 
	{Barkaoui}, K. and {Burgasser}, A. and {Burleigh}, M.~R. and 
	{Carey}, S.~J. and {Chaushev}, A. and {Copperwheat}, C.~M. and 
	{Delrez}, L. and {Fernandes}, C.~S. and {Holdsworth}, D.~L. and 
	{Kotze}, E.~J. and {Van Grootel}, V. and {Almleaky}, Y. and 
	{Benkhaldoun}, Z. and {Magain}, P. and {Queloz}, D.},
  title = {{Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1}},
  journal = {\nat},
  archiveprefix = {arXiv},
  eprint = {1703.01424},
  primaryclass = {astro-ph.EP},
  year = 2017,
  volume = 542,
  pages = {456-460},
  abstract = {{One aim of modern astronomy is to detect temperate, Earth-like
exoplanets that are well suited for atmospheric characterization.
Recently, three Earth-sized planets were detected that transit (that is,
pass in front of) a star with a mass just eight per cent that of the
Sun, located 12 parsecs away. The transiting configuration of these
planets, combined with the Jupiter-like size of their host
star{\mdash}named TRAPPIST-1{\mdash}makes possible in-depth studies of
their atmospheric properties with present-day and future astronomical
facilities. Here we report the results of a photometric monitoring
campaign of that star from the ground and space. Our observations reveal
that at least seven planets with sizes and masses similar to those of
Earth revolve around TRAPPIST-1. The six inner planets form a
near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04,
6.06, 9.1 and 12.35 days) are near-ratios of small integers. This
architecture suggests that the planets formed farther from the star and
migrated inwards. Moreover, the seven planets have equilibrium
temperatures low enough to make possible the presence of liquid water on
their surfaces.
  doi = {10.1038/nature21360},
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  author = {{Lefèvre}, M. and {Spiga}, A. and {Lebonnois}, S.},
  title = {{Three-dimensional turbulence-resolving modeling of the Venusian cloud layer and induced gravity waves}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {3-D mesoscale modeling, Venus, convective cloud layer, gravity waves},
  year = 2017,
  volume = 122,
  pages = {134-149},
  abstract = {{The impact of the cloud convective layer of the atmosphere of Venus on
the global circulation remains unclear. The recent observations of
gravity waves at the top of the cloud by the Venus Express mission
provided some answers. These waves are not resolved at the scale of
global circulation models (GCM); therefore, we developed an
unprecedented 3-D turbulence-resolving large-eddy simulations (LES)
Venusian model using the Weather Research and Forecast terrestrial
model. The forcing consists of three different heating rates: two
radiative ones for solar and infrared and one associated with the
adiabatic cooling/warming of the global circulation. The rates are
extracted from the Laboratoire de Météorlogie Dynamique
Venus GCM using two different cloud models. Thus, we are able to
characterize the convection and associated gravity waves in function of
latitude and local time. To assess the impact of the global circulation
on the convective layer, we used rates from a 1-D radiative-convective
model. The resolved layer, taking place between 1.0 {\times}
10$^{5}$ and 3.8 {\times} 10$^{4}$ Pa (48-53 km), is
organized as polygonal closed cells of about 10 km wide with vertical
wind of several meters per second. The convection emits gravity waves
both above and below the convective layer leading to temperature
perturbations of several tenths of kelvin with vertical wavelength
between 1 and 3 km and horizontal wavelength from 1 to 10 km. The
thickness of the convective layer and the amplitudes of waves are
consistent with observations, though slightly underestimated. The global
dynamics heating greatly modify the convective layer.
  doi = {10.1002/2016JE005146},
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  author = {{Gilli}, G. and {Lebonnois}, S. and {Gonz{\'a}lez-Galindo}, F. and 
	{L{\'o}pez-Valverde}, M.~A. and {Stolzenbach}, A. and {Lefèvre}, F. and 
	{Chaufray}, J.~Y. and {Lott}, F.},
  title = {{Thermal structure of the upper atmosphere of Venus simulated by a ground-to-thermosphere GCM}},
  journal = {\icarus},
  year = 2017,
  volume = 281,
  pages = {55-72},
  abstract = {{We present here the thermal structure of the upper atmosphere of Venus
predicted by a full self-consistent Venus General Circulation Model
(VGCM) developed at Laboratoire de Météorologie Dynamique
(LMD) and extended up to the thermosphere of the planet. Physical and
photochemical processes relevant at those altitudes, plus a
non-orographic GW parameterisation, have been added. All those
improvements make the LMD-VGCM the only existing ground-to-thermosphere
3D model for Venus: a unique tool to investigate the atmosphere of Venus
and to support the exploration of the planet by remote sounding. The aim
of this paper is to present the model reference results, to describe the
role of radiative, photochemical and dynamical effects in the observed
thermal structure in the upper mesosphere/lower thermosphere of the
planet. The predicted thermal structure shows a succession of warm and
cold layers, as recently observed. A cooling trend with increasing
latitudes is found during daytime at all altitudes, while at nighttime
the trend is inverse above about 110  km, with an atmosphere up to 15 K
warmer towards the pole. The latitudinal variation is even smaller at
the terminator, in agreement with observations. Below about 110  km, a
nighttime warm layer whose intensity decreases with increasing latitudes
is predicted by our GCM. A comparison of model results with a selection
of recent measurements shows an overall good agreement in terms of
trends and order of magnitude. Significant data-model discrepancies may
be also discerned. Among them, thermospheric temperatures are about
40-50 K colder and up to 30 K warmer than measured at terminator and at
nighttime, respectively. The altitude layer of the predicted mesospheric
local maximum (between 100 and 120  km) is also higher than observed.
Possible interpretations are discussed and several sensitivity tests
performed to understand the data-model discrepancies and to propose
future model improvements.
  doi = {10.1016/j.icarus.2016.09.016},
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