@comment{{This file has been generated by bib2bib 1.94}}
@comment{{Command line: /usr/bin/bib2bib --quiet -c 'not journal:"Discussions"' -c year=2014 -c $type="ARTICLE" -oc pub2014.txt -ob pub2014.bib}}
  author = {{Mousis}, O. and {Fletcher}, L.~N. and {Lebreton}, J.-P. and 
	{Wurz}, P. and {Cavalié}, T. and {Coustenis}, A. and {Courtin}, R. and 
	{Gautier}, D. and {Helled}, R. and {Irwin}, P.~G.~J. and {Morse}, A.~D. and 
	{Nettelmann}, N. and {Marty}, B. and {Rousselot}, P. and {Venot}, O. and 
	{Atkinson}, D.~H. and {Waite}, J.~H. and {Reh}, K.~R. and {Simon}, A.~A. and 
	{Atreya}, S. and {André}, N. and {Blanc}, M. and {Daglis}, I.~A. and 
	{Fischer}, G. and {Geppert}, W.~D. and {Guillot}, T. and {Hedman}, M.~M. and 
	{Hueso}, R. and {Lellouch}, E. and {Lunine}, J.~I. and {Murray}, C.~D. and 
	{O`Donoghue}, J. and {Rengel}, M. and {S{\'a}nchez-Lavega}, A. and 
	{Schmider}, F.-X. and {Spiga}, A. and {Spilker}, T. and {Petit}, J.-M. and 
	{Tiscareno}, M.~S. and {Ali-Dib}, M. and {Altwegg}, K. and {Bolton}, S.~J. and 
	{Bouquet}, A. and {Briois}, C. and {Fouchet}, T. and {Guerlet}, S. and 
	{Kostiuk}, T. and {Lebleu}, D. and {Moreno}, R. and {Orton}, G.~S. and 
	{Poncy}, J.},
  title = {{Scientific rationale for Saturn's in situ exploration}},
  journal = {\planss},
  archiveprefix = {arXiv},
  eprint = {1404.4811},
  primaryclass = {astro-ph.EP},
  keywords = {Entry probe, Saturn atmosphere, Giant planet formation, Solar system formation, In situ measurements, Elemental and isotopic composition},
  year = 2014,
  volume = 104,
  pages = {29-47},
  abstract = {{Remote sensing observations meet some limitations when used to study the
bulk atmospheric composition of the giant planets of our solar system. A
remarkable example of the superiority of in situ probe measurements is
illustrated by the exploration of Jupiter, where key measurements such
as the determination of the noble gases' abundances and the precise
measurement of the helium mixing ratio have only been made available
through in situ measurements by the Galileo probe. This paper describes
the main scientific goals to be addressed by the future in situ
exploration of Saturn placing the Galileo probe exploration of Jupiter
in a broader context and before the future probe exploration of the more
remote ice giants. In situ exploration of Saturn's atmosphere addresses
two broad themes that are discussed throughout this paper: first, the
formation history of our solar system and second, the processes at play
in planetary atmospheres. In this context, we detail the reasons why
measurements of Saturn's bulk elemental and isotopic composition would
place important constraints on the volatile reservoirs in the protosolar
nebula. We also show that the in situ measurement of CO (or any other
disequilibrium species that is depleted by reaction with water) in
Saturn's upper troposphere may help constraining its bulk O/H ratio. We
compare predictions of Jupiter and Saturn's bulk compositions from
different formation scenarios, and highlight the key measurements
required to distinguish competing theories to shed light on giant planet
formation as a common process in planetary systems with potential
applications to most extrasolar systems. In situ measurements of
Saturn's stratospheric and tropospheric dynamics, chemistry and
cloud-forming processes will provide access to phenomena unreachable to
remote sensing studies. Different mission architectures are envisaged,
which would benefit from strong international collaborations, all based
on an entry probe that would descend through Saturn's stratosphere and
troposphere under parachute down to a minimum of 10 bar of atmospheric
pressure. We finally discuss the science payload required on a Saturn
probe to match the measurement requirements.
  doi = {10.1016/j.pss.2014.09.014},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Hinson}, D.~P. and {Asmar}, S.~W. and {Kahan}, D.~S. and {Akopian}, V. and 
	{Haberle}, R.~M. and {Spiga}, A. and {Schofield}, J.~T. and 
	{Kleinb{\"o}hl}, A. and {Abdou}, W.~A. and {Lewis}, S.~R. and 
	{Paik}, M. and {Maalouf}, S.~G.},
  title = {{Initial results from radio occultation measurements with the Mars Reconnaissance Orbiter: A nocturnal mixed layer in the tropics and comparisons with polar profiles from the Mars Climate Sounder}},
  journal = {\icarus},
  keywords = {Mars, atmosphere, climate, Atmospheres, dynamics, Meteorology},
  year = 2014,
  volume = 243,
  pages = {91-103},
  abstract = {{The Mars Reconnaissance Orbiter (MRO) performs radio occultation (RO)
measurements on selected orbits, generally once per day. We have
retrieved atmospheric profiles from two subsets of data, yielding a
variety of new results that illustrate the scientific value of the
observations. One set of measurements sounded the tropics in northern
summer at a local time {\sim}1 h before sunrise. Some of these profiles
contain an unexpected layer of neutral stability with a depth of {\sim}4
km and a pressure at its upper boundary of {\sim}160 Pa. The mixed layer
is bounded above by a temperature inversion and below by another strong
inversion adjacent to the surface. This type of structure is observed
near Gale Crater, in the Tharsis region, and at a few other locations,
whereas profiles in Amazonis Planitia and Elysium Planitia show no sign
of a detached mixed layer with an overlying inversion. We supplemented
the measurements with numerical simulations by the NASA Ames Mars
General Circulation Model, which demonstrate that water ice clouds can
generate this distinctive type of temperature structure through their
influence on radiative transfer at infrared wavelengths. In particular,
the simulations predict the presence of a nocturnal cloud layer in the
Tharsis region at a pressure of {\sim}150 Pa ({\sim}10 km above the
surface), and the nighttime radiative cooling at cloud level is
sufficient to produce a temperature inversion above the cloud as well as
convective instability below the cloud, consistent with the
observations. The second set of measurements sounded mid-to-high
northern latitudes in spring, when carefully coordinated observations by
the MRO Mars Climate Sounder (MCS) are also available. The differences
between the RO and MCS temperature profiles are generally consistent
with the expected performance of the two instruments. Within this set of
21 comparisons the average temperature difference is less than 1 K where
the aerosol opacities are smaller than 10$^{-3}$km$^{-1}$ ,
at pressures of 10-50 Pa, whereas it increases to {\sim}2 K where the
aerosol opacities exceed this threshold, at pressures of 50-300 Pa. The
standard deviation of the temperature difference is {\sim}2 K,
independent of pressure. The second set of RO measurements also provides
unique information about the stability of the annual CO$_{2}$
cycle and the dynamics near the edge of the seasonal CO$_{2}$ ice
  doi = {10.1016/j.icarus.2014.09.019},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Charnay}, B. and {Forget}, F. and {Tobie}, G. and {Sotin}, C. and 
	{Wordsworth}, R.},
  title = {{Titan's past and future: 3D modeling of a pure nitrogen atmosphere and geological implications}},
  journal = {\icarus},
  archiveprefix = {arXiv},
  eprint = {1407.1791},
  primaryclass = {astro-ph.EP},
  year = 2014,
  volume = 241,
  pages = {269-279},
  abstract = {{Several clues indicate that Titan's atmosphere has been depleted in
methane during some period of its history, possibly as recently as 0.5-1
billion years ago. It could also happen in the future. Under these
conditions, the atmosphere becomes only composed of nitrogen with a
range of temperature and pressure allowing liquid or solid nitrogen to
condense. Here, we explore these exotic climates throughout Titan's
history with a 3D Global Climate Model (GCM) including the nitrogen
cycle and the radiative effect of nitrogen clouds. We show that for the
last billion years, only small polar nitrogen lakes should have formed.
Yet, before 1 Ga, a significant part of the atmosphere could have
condensed, forming deep nitrogen polar seas, which could have flowed and
flooded the equatorial regions. Alternatively, nitrogen could be frozen
on the surface like on Triton, but this would require an initial surface
albedo higher than 0.65 at 4 Ga. Such a state could be stable even today
if nitrogen ice albedo is higher than this value. According to our
model, nitrogen flows and rain may have been efficient to erode the
surface. Thus, we can speculate that a paleo-nitrogen cycle may explain
the erosion and the age of Titan's surface, and may have produced some
of the present valley networks and shorelines. Moreover, by diffusion of
liquid nitrogen in the crust, a paleo-nitrogen cycle could be
responsible of the flattening of the polar regions and be at the origin
of the methane outgassing on Titan.
  doi = {10.1016/j.icarus.2014.07.009},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Navarro}, T. and {Forget}, F. and {Millour}, E. and {Greybush}, S.~J.
  title = {{Detection of detached dust layers in the Martian atmosphere from their thermal signature using assimilation}},
  journal = {\grl},
  keywords = {Mars, atmosphere, dust, assimilation},
  year = 2014,
  volume = 41,
  pages = {6620-6626},
  abstract = {{Airborne dust modifies the thermal structure of the Martian atmosphere.
The Mars Climate Sounder (MCS) first revealed local maxima of dust mass
mixing ratio detached from the surface, not reproduced by global climate
models (GCM). In this paper, the thermal signature of such detached
layers is detected using data assimilation, an optimal combination of a
GCM and observations. As dust influences the atmospheric temperatures,
MCS temperature profiles are used to estimate the amount of dust in the
atmosphere. Data assimilation of only MCS temperature information
reproduces detached dust layers, independently confirming MCS's direct
observations of dust. The resulting analyzed state has a smaller bias
than an assimilation that does not estimate dust. This makes it a
promising technique for Martian data assimilation, which is intended to
support weather forecasting and weather research on Mars.
  doi = {10.1002/2014GL061377},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Herny}, C. and {Massé}, M. and {Bourgeois}, O. and {Carpy}, S. and 
	{Le Mouélic}, S. and {Appéré}, T. and {Smith}, I.~B. and 
	{Spiga}, A. and {Rodriguez}, S.},
  title = {{Sedimentation waves on the Martian North Polar Cap: Analogy with megadunes in Antarctica}},
  journal = {Earth and Planetary Science Letters},
  keywords = {ice sedimentation waves, megadunes, polar caps, Mars, Antarctica},
  year = 2014,
  volume = 403,
  pages = {56-66},
  abstract = {{Complex interactions between katabatic winds and the cryosphere may lead
to the formation of sedimentation waves at the surface of ice sheets.
These have been first described and named snow megadunes in Antarctica.
Here we use topographic data, optical images, subsurface radar soundings
and spectroscopic data acquired by Mars orbiters, to show that the
surface of the Martian North Polar Cap displays two superimposed sets of
sedimentation waves with differing wavelengths. These sedimentation
waves have similarities with Antarctic snow megadunes regarding their
surface morphology, texture, grain size asymmetry, and internal
stratigraphic architecture. Both sets of Martian sedimentation waves
present young ice and occasional sastrugi fields, indicative of net
accumulation, on their shallow-dipping upwind sides, their tops and the
intervening troughs. Old layers of dusty ice, indicative of net
ablation, are exhumed on the steep-dipping downwind sides of the larger
waves. Smooth surfaces of coarse-grained ice, indicative of reduced
accumulation associated with sublimation metamorphism, cover the
steep-dipping downwind sides of the smaller waves. These surface
characteristics and the internal stratigraphy revealed by radar
soundings are consistent with the interpretation that both sets of
Martian sedimentation waves grow and migrate upwind in response to the
development of periodic accumulation/ablation patterns controlled by
katabatic winds. The recognition of these sedimentation waves provides
the basis for the development of a common model of ice/wind interaction
at the surface of Martian and terrestrial glaciers. Martian smaller
waves, characterized by reduced net accumulation on their downwind
sides, are analogous to Antarctic snow megadunes that have been
described so far. A terrestrial equivalent remains to be discovered for
the larger Martian waves, characterized by net ablation on their
downwind sides.
  doi = {10.1016/j.epsl.2014.06.033},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Guerlet}, S. and {Spiga}, A. and {Sylvestre}, M. and {Indurain}, M. and 
	{Fouchet}, T. and {Leconte}, J. and {Millour}, E. and {Wordsworth}, R. and 
	{Capderou}, M. and {Bézard}, B. and {Forget}, F.},
  title = {{Global climate modeling of Saturn{\rsquo}s atmosphere. Part I: Evaluation of the radiative transfer model}},
  journal = {\icarus},
  year = 2014,
  volume = 238,
  pages = {110-124},
  abstract = {{We have developed and optimized a seasonal, radiative-convective model
of Saturn{\rsquo}s upper troposphere and stratosphere. It is used to
investigate Saturn{\rsquo}s radiatively-forced thermal structure between
3 and 10$^{-6}$ bar, and is intended to be included in a Saturn
global climate model (GCM), currently under development. The main
elements of the radiative transfer model are detailed as well as the
sensitivity to spectroscopic parameters, hydrocarbon abundances, aerosol
properties, oblateness, and ring shadowing effects. The vertical
temperature structure and meridional seasonal contrasts obtained by the
model are then compared to Cassini/CIRS observations. Several
significant model-observation mismatches reveal that Saturn{\rsquo}s
atmosphere departs from radiative equilibrium. For instance, we find
that the modeled temperature profile is close to isothermal above the
2-mbar level, while the temperature retrieved from ground-based or
Cassini/CIRS data continues to increase with altitude. Also, no local
temperature minimum associated to the ring shadowing is observed in the
data, while the model predicts stratospheric temperatures 10 K to 20 K
cooler than in the absence of rings at winter tropical latitudes. These
anomalies are strong evidence that processes other that radiative
heating and cooling control Saturn{\rsquo}s stratospheric thermal
structure. Finally, the model is used to study the warm stratospheric
anomaly triggered after the 2010 Great White Spot. Comparison with
recent Cassini/CIRS observations suggests that the rapid cooling phase
of this warm {\ldquo}beacon{\rdquo} in May-June 2011 can be explained by
radiative processes alone. Observations on a longer timeline are needed
to better characterize and understand its long-term evolution.
  doi = {10.1016/j.icarus.2014.05.010},
  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. and {Yagi}, M. and {Blelly}, P.-L. and {Witasse}, O.
  title = {{Three-dimensional Martian ionosphere model: II. Effect of transport processes due to pressure gradients}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Mars, ionosphere, dynamics},
  year = 2014,
  volume = 119,
  pages = {1614-1636},
  abstract = {{To study the transport of the ionospheric plasma on Mars, we have
included a 3-D multifluid dynamical core in a Martian general
circulation model. Vertical transport modifies the ion density above
\~{}160 km on the dayside, especially the ions produced at high altitudes
like O$^{+}$, N$^{+}$, and C$^{+}$. Near the exobase,
the dayside to nightside flow velocity reaches few hundreds of m/s, due
to a large horizontal pressure gradient. Comparison with Mars
Express/Analyzer of Space Plasmas and Energetic Atoms-3 measurements
between 290 and 500 km suggests that this flow could account for at
least 20\% of the flow produced by the solar wind. This flow is not
sufficient to populate substantially the nightside ionosphere at high
altitudes, in agreement with recent observations, because of a strong
nightside downward flow produced by vertical pressure gradient. The
O$_{2}$$^{+}$ and NO$^{+}$ ion densities on the
nightside at low altitudes (\~{}130 km) are modified by this downward flow,
compared to simulated densities without ion dynamics, while other ions
are lost by chemical reactions. Variability at different time scales
(diurnal, seasonal, and solar cycles) are studied. We simulate diurnal
and seasonal variations of the ionospheric composition due to the
variability of the neutral atmosphere and solar flux at the top of the
atmosphere. The ionospheric dynamics are not strongly affected by
seasons and solar cycles, and the retroaction of the ionosphere on the
neutral atmosphere temperature and velocity is negligible compared to
other physical processes below the exobase.
  doi = {10.1002/2013JE004551},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Navarro}, T. and {Madeleine}, J.-B. and {Forget}, F. and {Spiga}, A. and 
	{Millour}, E. and {Montmessin}, F. and {M{\"a}{\"a}tt{\"a}nen}, A.
  title = {{Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds}},
  journal = {Journal of Geophysical Research (Planets)},
  archiveprefix = {arXiv},
  eprint = {1310.1010},
  primaryclass = {astro-ph.EP},
  keywords = {Mars, atmosphere, climate, global climate model, clouds, water},
  year = 2014,
  volume = 119,
  pages = {1479-1495},
  abstract = {{Water ice clouds play a key role in the radiative transfer of the
Martian atmosphere, impacting its thermal structure, its circulation,
and, in turn, the water cycle. Recent studies including the radiative
effects of clouds in global climate models (GCMs) have found that the
corresponding feedbacks amplify the model defaults. In particular, it
prevents models with simple microphysics from reproducing even the basic
characteristics of the water cycle. Within that context, we propose a
new implementation of the water cycle in GCMs, including a detailed
cloud microphysics taking into account nucleation on dust particles, ice
particle growth, and scavenging of dust particles due to the
condensation of ice. We implement these new methods in the Laboratoire
de Météorologie Dynamique GCM and find satisfying
agreement with the Thermal Emission Spectrometer observations of both
water vapor and cloud opacities, with a significant improvement when
compared to GCMs taking into account radiative effects of water ice
clouds without this implementation. However, a lack of water vapor in
the tropics after Ls = 180{\deg} is persistent in simulations compared to
observations, as a consequence of aphelion cloud radiative effects
strengthening the Hadley cell. Our improvements also allow us to explore
questions raised by recent observations of the Martian atmosphere.
Supersaturation above the hygropause is predicted in line with
Spectroscopy for Investigation of Characteristics of the Atmosphere of
Mars observations. The model also suggests for the first time that the
scavenging of dust by water ice clouds alone fails to fully account for
the detached dust layers observed by the Mars Climate Sounder.
  doi = {10.1002/2013JE004550},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Listowski}, C. and {M{\"a}{\"a}tt{\"a}nen}, A. and {Montmessin}, F. and 
	{Spiga}, A. and {Lefèvre}, F.},
  title = {{Modeling the microphysics of CO$_{2}$ ice clouds within wave-induced cold pockets in the martian mesosphere}},
  journal = {\icarus},
  year = 2014,
  volume = 237,
  pages = {239-261},
  abstract = {{Mesospheric CO$_{2}$ ice clouds on Mars are simulated with a 1D
microphysical model, which includes a crystal growth rate adapted to
high supersaturations encountered in the martian mesosphere.
Observational constraints (crystal radius and opacity) exist for these
clouds observed during the day around the equator at {\tilde}60-80 km
altitude. Nighttime mesospheric clouds interpreted as CO$_{2}$ ice
clouds have also been characterized at low southern latitudes, at
{\tilde}90-100 km altitude. From modeling and observational evidence, it is
believed that mesospheric clouds are formed within temperature minima
created by thermal tides, where gravity wave propagation allows for the
creation of supersaturated layers (cold pockets). Thus, temperature
profiles perturbed by gravity waves are used in the model to initiate
nucleation and maintain growth of CO$_{2}$ ice crystals. We show
that it is possible to reproduce the observed effective radii for
daytime and nighttime clouds. Crystal sizes are mainly governed by the
altitude where the cloud forms, and by the amplitude of supersaturation.
The temporal and spatial behavior of the cloud is controlled by the
extent and lifetime of the cold pocket. The cloud evaporates fast after
the cold pocket has vanished, implying a strong correlation between
gravity wave activity and CO$_{2}$ cloud formation. Simulated
opacities remain far below the observed ones as long as typical dust
conditions are used. In the case of the lower daytime clouds, the
enhanced mesospheric dust loading typically reached during dust storm
conditions, allows for greater cloud opacities, close to observed
values, by supplying the atmosphere with condensation nuclei. However,
CO$_{2}$ ice clouds are not detected during the dust storm season,
and, because of fast sedimentation of dust particles, an exogenous
supply (meteoritic flux) appears necessary to explain opacities of both
daytime and nighttime mesospheric CO$_{2}$ ice clouds along their
whole period of observation.
  doi = {10.1016/j.icarus.2014.04.022},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Steele}, L.~J. and {Lewis}, S.~R. and {Patel}, M.~R. and {Montmessin}, F. and 
	{Forget}, F. and {Smith}, M.~D.},
  title = {{The seasonal cycle of water vapour on Mars from assimilation of Thermal Emission Spectrometer data}},
  journal = {\icarus},
  year = 2014,
  volume = 237,
  pages = {97-115},
  abstract = {{We present for the first time an assimilation of Thermal Emission
Spectrometer (TES) water vapour column data into a Mars global climate
model (MGCM). We discuss the seasonal cycle of water vapour, the
processes responsible for the observed water vapour distribution, and
the cross-hemispheric water transport. The assimilation scheme is shown
to be robust in producing consistent reanalyses, and the global water
vapour column error is reduced to around 2-4 pr {$\mu$}m depending on
season. Wave activity is shown to play an important role in the water
vapour distribution, with topographically steered flows around the
Hellas and Argyre basins acting to increase transport in these regions
in all seasons. At high northern latitudes, zonal wavenumber 1 and 2
stationary waves during northern summer are responsible for spreading
the sublimed water vapour away from the pole. Transport by the zonal
wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia
Terra and, combined with the effects of western boundary currents, this
leads to peak water vapour column abundances here as observed by
numerous spacecraft. A net transport of water to the northern hemisphere
over the course of one Mars year is calculated, primarily because of the
large northwards flux of water vapour which occurs during the local dust
storm around L$_{S}$=240-260{\deg}. Finally, outlying frost
deposits that surround the north polar cap are shown to be important in
creating the peak water vapour column abundances observed during
northern summer.
  doi = {10.1016/j.icarus.2014.04.017},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Madeleine}, J.-B. and {Head}, J.~W. and {Forget}, F. and {Navarro}, T. and 
	{Millour}, E. and {Spiga}, A. and {Cola{\"i}tis}, A. and {M{\"a}{\"a}tt{\"a}nen}, A. and 
	{Montmessin}, F. and {Dickson}, J.~L.},
  title = {{Recent Ice Ages on Mars: The role of radiatively active clouds and cloud microphysics}},
  journal = {\grl},
  keywords = {Glaciation, Mars, Paleoclimate, Climate model, Clouds, Climate},
  year = 2014,
  volume = 41,
  pages = {4873-4879},
  abstract = {{Global climate models (GCMs) have been successfully employed to explain
the origin of many glacial deposits on Mars. However, the
latitude-dependent mantle (LDM), a dust-ice mantling deposit that is
thought to represent a recent ``Ice Age,'' remains poorly explained by
GCMs. We reexamine this question by considering the effect of
radiatively active water-ice clouds (RACs) and cloud microphysics. We
find that when obliquity is set to 35{\deg}, as often occurred in the
past 2 million years, warming of the atmosphere and polar caps by clouds
modifies the water cycle and leads to the formation of a several
centimeter-thick ice mantle poleward of 30{\deg} in each hemisphere
during winter. This mantle can be preserved over the summer if increased
atmospheric dust content obscures the surface and provides dust nuclei
to low-altitude clouds. We outline a scenario for its deposition and
preservation that compares favorably with the characteristics of the
  doi = {10.1002/2014GL059861},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Montabone}, L. and {Marsh}, K. and {Lewis}, S.~R. and {Read}, P.~L. and 
	{Smith}, M.~D. and {Holmes}, J. and {Spiga}, A. and {Lowe}, D. and 
	{Pamment}, A.},
  title = {{The Mars Analysis Correction Data Assimilation (MACDA) Dataset V1.0}},
  journal = {Geoscience Data Journal},
  year = 2014,
  volume = 1,
  pages = {129-139},
  abstract = {{The Mars Analysis Correction Data Assimilation (MACDA) dataset version
1.0 contains the reanalysis of fundamental atmospheric and surface
variables for the planet Mars covering a period of about three Martian
years (a Martian year is about 1.88 terrestrial years). This has been
produced by data assimilation of observations from NASA's Mars Global
Surveyor (MGS) spacecraft during its science mapping phase (February
1999-August 2004). In particular, we have used retrieved thermal profiles 
and total dust optical depths from the Thermal Emission Spectrometer (TES) 
on board MGS. Data have been assimilated into a Mars global climate model 
(MGCM) using the Analysis Correction scheme developed at the UK 
Meteorological Office. The MGCM used is the UK spectral version of 
the Laboratoire de Météorologie Dynamique (LMD, Paris, France)
MGCM. MACDA is a joint project of the University of Oxford and The Open
University in the UK.
  doi = {10.1002/gdj3.13},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Dils}, B. and {Buchwitz}, M. and {Reuter}, M. and {Schneising}, O. and 
	{Boesch}, H. and {Parker}, R. and {Guerlet}, S. and {Aben}, I. and 
	{Blumenstock}, T. and {Burrows}, J.~P. and {Butz}, A. and {Deutscher}, N.~M. and 
	{Frankenberg}, C. and {Hase}, F. and {Hasekamp}, O.~P. and {Heymann}, J. and 
	{De Mazière}, M. and {Notholt}, J. and {Sussmann}, R. and 
	{Warneke}, T. and {Griffith}, D. and {Sherlock}, V. and {Wunch}, D.
  title = {{The Greenhouse Gas Climate Change Initiative (GHG-CCI): comparative validation of GHG-CCI SCIAMACHY/ENVISAT and TANSO-FTS/GOSAT CO$_{2}$ and CH$_{4}$ retrieval algorithm products with measurements from the TCCON}},
  journal = {Atmospheric Measurement Techniques},
  year = 2014,
  volume = 7,
  pages = {1723-1744},
  abstract = {{Column-averaged dry-air mole fractions of carbon dioxide and methane
have been retrieved from spectra acquired by the TANSO-FTS (Thermal And
Near-infrared Sensor for carbon Observations-Fourier Transform
Spectrometer) and SCIAMACHY (Scanning Imaging Absorption Spectrometer
for Atmospheric Cartography) instruments on board GOSAT (Greenhouse
gases Observing SATellite) and ENVISAT (ENVIronmental SATellite),
respectively, using a range of European retrieval algorithms. These
retrievals have been compared with data from ground-based
high-resolution Fourier transform spectrometers (FTSs) from the Total
Carbon Column Observing Network (TCCON). The participating algorithms
are the weighting function modified differential optical absorption
spectroscopy (DOAS) algorithm (WFMD, University of Bremen), the Bremen
optimal estimation DOAS algorithm (BESD, University of Bremen), the
iterative maximum a posteriori DOAS (IMAP, Jet Propulsion Laboratory
(JPL) and Netherlands Institute for Space Research algorithm (SRON)),
the proxy and full-physics versions of SRON's RemoTeC algorithm (SRPR
and SRFP, respectively) and the proxy and full-physics versions of the
University of Leicester's adaptation of the OCO (Orbiting Carbon
Observatory) algorithm (OCPR and OCFP, respectively). The goal of this
algorithm inter-comparison was to identify strengths and weaknesses of
the various so-called round- robin data sets generated with the various
algorithms so as to determine which of the competing algorithms would
proceed to the next round of the European Space Agency's (ESA)
Greenhouse Gas Climate Change Initiative (GHG-CCI) project, which is the
generation of the so-called Climate Research Data Package (CRDP), which
is the first version of the Essential Climate Variable (ECV) ``greenhouse
gases'' (GHGs). 

For XCO$_{2}$, all algorithms reach the precision requirements for inverse modelling ($\lt$ 8 ppm), with only WFMD having a lower precision (4.7 ppm) than the other algorithm products (2.4-2.5 ppm). When looking at the seasonal relative accuracy (SRA, variability of the bias in space and time), none of the algorithms have reached the demanding $\lt$ 0.5 ppm threshold.

For XCH$_{4}$, the precision for both SCIAMACHY products (50.2 ppb for IMAP and 76.4 ppb for WFMD) fails to meet the $\lt$ 34 ppb threshold for inverse modelling, but note that this work focusses on the period after the 2005 SCIAMACHY detector degradation. The GOSAT XCH$_{4}$ precision ranges between 18.1 and 14.0 ppb. Looking at the SRA, all GOSAT algorithm products reach the $\lt$ 10 ppm threshold (values ranging between 5.4 and 6.2 ppb). For SCIAMACHY, IMAP and WFMD have a SRA of 17.2 and 10.5 ppb, respectively. }}, doi = {10.5194/amt-7-1723-2014}, adsurl = {}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }
  author = {{Sinclair}, J.~A. and {Irwin}, P.~G.~J. and {Fletcher}, L.~N. and 
	{Greathouse}, T. and {Guerlet}, S. and {Hurley}, J. and {Merlet}, C.
  title = {{From Voyager-IRIS to Cassini-CIRS: Interannual variability in Saturn{\rsquo}s stratosphere?}},
  journal = {\icarus},
  year = 2014,
  volume = 233,
  pages = {281-292},
  abstract = {{We present an intercomparison of Saturn{\rsquo}s stratosphere between
Voyager 1-IRIS observations in 1980 and Cassini-CIRS observations in
2009 and 2010. Over a saturnian year ({\sim}29.5 years) has now passed
since the Voyager flybys of Saturn in 1980/1981. Cassini observations in
2009/2010 capture Saturn in the same season as Voyager observations
(just after the vernal equinox) but one year later. Any differences in
Saturn{\rsquo}s atmospheric properties implied by a comparison of these
two datasets could therefore reveal the extent of interannual
variability. We retrieve temperature and stratospheric acetylene and
ethane concentrations from Voyager 1-IRIS ({$\Delta$}{$\nu$}{\tilde}=4.3
cm$^{-1}$) observations in 1980 and Cassini-CIRS
({$\Delta$}{$\nu$}{\tilde}=15.5 cm$^{-1}$) {\lsquo}FIRMAP{\rsquo}
observations in 2009 and 2010. We observe a difference in temperature at
the equator of 7.1 {\plusmn} 1.2 K at the 2.1-mbar level that implies
that the two datasets have captured Saturn{\rsquo}s semiannual
oscillation (SSAO) in a slightly different phase suggesting that its
period is more quasi-semiannual. Elevated concentrations of acetylene at
25{\deg}S in 1980 with respect to 2010 imply stronger downwelling at the
former date which may also be explained by a difference in the phase of
the SSAO and its dynamical forcing at low latitudes. At high-southern
and high-northern latitudes, stratospheric temperatures and hydrocarbon
concentrations appear elevated in 1980 with respect to 2009/2010. This
could be an artefact of the low signal-to-noise ratio of the
corresponding observations but might also be explained by increased
auroral activity during solar maximum in 1980.
  doi = {10.1016/j.icarus.2014.02.009},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Audouard}, J. and {Poulet}, F. and {Vincendon}, M. and {Bibring}, J.-P. and 
	{Forget}, F. and {Langevin}, Y. and {Gondet}, B.},
  title = {{Mars surface thermal inertia and heterogeneities from OMEGA/MEX}},
  journal = {\icarus},
  year = 2014,
  volume = 233,
  pages = {194-213},
  abstract = {{The thermophysical structure of the martian surface is the result of
various processes that have shaped the martian surface through time.
Previous dedicated heliosynchronous measurements of the thermal infrared
(IR) flux of the martian surface have revealed the diversity of martian
surface thermal properties, as well as its complexity linked to the
heterogeneous nature of terrains. We present the first retrieval of
thermophysical properties of the martian surface using near-infrared
(NIR) Observatoire pour la Minéralogie, l{\rsquo}Eau, les Glaces
et l{\rsquo}Activité (OMEGA) onboard Mars Express (MEX) thermal
measurements from 5 to 5.1 {$\mu$}m. MEX orbit around Mars is elliptical
and therefore OMEGA has performed surface temperature measurements at
various local times and seasons over more than 4 full martian years. We
have developed a method to exploit these unprecedented measurements
using a one-dimensional energy balance code derived from a Global
Climate Model that allows retrieval of the thermal properties of the
martian surface using OMEGA data. Regional maps of the thermal inertia
at a resolution up to 32 pixels per degree and a global map at 4 pixels
per degree are presented. OMEGA-derived thermal inertia values agree
with previous mappings by the Thermal Emission Spectrometer (TES)
onboard Mars Global Surveyor (MGS) and Thermal Emission Imaging
Spectrometer (THEMIS) onboard Mars Odyssey and highlight the key role of
dust for the thermal behavior of the martian surface. OMEGA directly
reveals for the first time some diurnal variations of apparent TI
attributable to surface heterogeneities at macroscopic scale and enables
to quantify these heterogeneities. In Nili Patera and Tharsis, local
surface heterogeneities are modeled with layering and horizontal
admixture of divergent slopes respectively.
  doi = {10.1016/j.icarus.2014.01.045},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Grassi}, D. and {Politi}, R. and {Ignatiev}, N.~I. and {Plainaki}, C. and 
	{Lebonnois}, S. and {Wolkenberg}, P. and {Montabone}, L. and 
	{Migliorini}, A. and {Piccioni}, G. and {Drossart}, P.},
  title = {{The Venus nighttime atmosphere as observed by the VIRTIS-M instrument. Average fields from the complete infrared data set}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Venus, Planetary atmospheres},
  year = 2014,
  volume = 119,
  pages = {837-849},
  abstract = {{We present and discuss here the average fields of the Venus atmosphere
derived from the nighttime observations in the 1960-2350 cm$^{-1}$
spectral range by the VIRTIS-M instrument on board the Venus Express
satellite. These fields include: (a) the air temperatures in the 1-100
mbar pressure range (\~{}85-65 km above the surface), (b) the altitude of
the clouds top, and (c) the average CO mixing ratio. A new retrieval
code based on the Bayesian formalism has been developed and validated on
simulated observations, to statistically assess the retrieval
capabilities of the scheme once applied to the VIRTIS data. The same
code has then been used to process the entire VIRTIS-M data set.
Resulting individual retrievals have been binned on the basis of local
time and latitude, to create average fields. Air temperature fields
confirm the general trends previously reported in Grassi et al. (2010),
using a simplified retrieval scheme and a more limited data set. At the
lowest altitudes probed by VIRTIS (\~{}65 km), air temperatures are
strongly asymmetric around midnight, with a pronounced minima at 3LT,
70{\deg}S. Moving to higher levels, the air temperatures first become
more uniform in local time (\~{}75 km), then display a colder region on the
evening side at the upper boundary of VIRTIS sensitivity range (\~{}80 km).
As already shown by Ignatiev et al. (2008) for the dayside, the cloud
effective altitude increases monotonically from the south pole to the
equator. However, the variations observed in night data are consistent
with an overall variation of just 1 km, much smaller than the 4 km
reported for the dayside. The cloud altitudes appear slightly higher on
the evening side. Both observations are consistent with a less vigorous
meridional circulation on the nightside of the planet. Carbon monoxide
is not strongly constrained by the VIRTIS-M data. However, average
fields present a clear maximum of 80 ppm around 60{\deg}S, well above the
retrieval uncertainty. Once the intrinsic low sensitivity of VIRTIS data
in the region of cold collar is kept in mind, this datum is consistent
with a [CO] enrichment toward the poles driven by meridional
  doi = {10.1002/2013JE004586},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Takagi}, H. and {Houweling}, S. and {Andres}, R.~J. and {Belikov}, D. and 
	{Bril}, A. and {Boesch}, H. and {Butz}, A. and {Guerlet}, S. and 
	{Hasekamp}, O. and {Maksyutov}, S. and {Morino}, I. and {Oda}, T. and 
	{O'Dell}, C.~W. and {Oshchepkov}, S. and {Parker}, R. and {Saito}, M. and 
	{Uchino}, O. and {Yokota}, T. and {Yoshida}, Y. and {Valsala}, V.
  title = {{Influence of differences in current GOSAT X$_{CO}$$_{2}$ retrievals on surface flux estimation}},
  journal = {\grl},
  keywords = {CO$_{2}$ sources and sinks, surface fluxes, inverse modeling, GOSAT, column CO$_{2}$ concentration},
  year = 2014,
  volume = 41,
  pages = {2598-2605},
  abstract = {{We investigated differences in the five currently-available datasets of
column-integrated CO$_{2}$ concentrations (XCO2) retrieved from
spectral soundings collected by Greenhouse gases Observing SATellite
(GOSAT) and assessed their impact on regional CO$_{2}$ flux
estimates. We did so by estimating the fluxes from each of the five XCO2
datasets combined with surface-based CO$_{2}$ data, using a single
inversion system. The five XCO2 datasets are available in raw and
bias-corrected versions, and we found that the bias corrections diminish
the range of the five coincident values by \~{}30\% on average. The
departures of the five individual inversion results (annual-mean
regional fluxes based on XCO2-surface combined data) from the
surface-data-only results were close to one another in some terrestrial
regions where spatial coverage by each XCO2 dataset was similar. The
mean of the five annual global land uptakes was 1.7 {\plusmn} 0.3 GtC
yr$^{-1}$, and they were all smaller than the value estimated from
the surface-based data alone.
  doi = {10.1002/2013GL059174},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Galli}, A. and {Guerlet}, S. and {Butz}, A. and {Aben}, I. and 
	{Suto}, H. and {Kuze}, A. and {Deutscher}, N.~M. and {Notholt}, J. and 
	{Wunch}, D. and {Wennberg}, P.~O. and {Griffith}, D.~W.~T. and 
	{Hasekamp}, O. and {Landgraf}, J.},
  title = {{The impact of spectral resolution on satellite retrieval accuracy of CO$_{2}$ and CH$_{4}$}},
  journal = {Atmospheric Measurement Techniques},
  year = 2014,
  volume = 7,
  pages = {1105-1119},
  abstract = {{The Fourier-transform spectrometer on board the Japanese GOSAT
(Greenhouse gases Observing SATellite) satellite offers an excellent
opportunity to study the impact of instrument resolution on retrieval
accuracy of CO$_{2}$ and CH$_{4}$. This is relevant to
further improve retrieval accuracy and to optimize the cost-benefit
ratio of future satellite missions for the remote sensing of greenhouse
gases. To address this question, we degrade GOSAT measurements with a
spectral resolution of {\ap} 0.24 cm$^{-1}$ step by step to a
resolution of 1.5 cm$^{-1}$. We examine the results by comparing
relative differences at various resolutions, by referring the results to
reference values from the Total Carbon Column Observing Network (TCCON),
and by calculating and inverting synthetic spectra for which the true
CO$_{2}$ and CH$_{4}$ columns are known. The main impacts of
degrading the spectral resolution are reproduced for all approaches
based on GOSAT measurements; pure forward model errors identified with
simulated measurements are much smaller. 

For GOSAT spectra, the most notable effect on CO$_{2}$ retrieval accuracy is the increase of the standard deviation of retrieval errors from 0.7 to 1.0\% when the spectral resolution is reduced by a factor of six. The retrieval biases against atmospheric water abundance and air mass become stronger with decreasing resolution. The error scatter increase for CH$_{4}$ columns is less pronounced. The selective degradation of single spectral windows demonstrates that the retrieval accuracy of CO$_{2}$ and CH$_{4}$ is dominated by the spectral range where the absorption lines of the target molecule are located. For both GOSAT and synthetic measurements, retrieval accuracy decreases with lower spectral resolution for a given signal-to-noise ratio, suggesting increasing interference errors. }}, doi = {10.5194/amt-7-1105-2014}, adsurl = {}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }
  author = {{Forget}, F. and {Leconte}, J.},
  title = {{Possible climates on terrestrial exoplanets}},
  journal = {Philosophical Transactions of the Royal Society of London Series A},
  archiveprefix = {arXiv},
  eprint = {1311.3101},
  primaryclass = {astro-ph.EP},
  year = 2014,
  volume = 372,
  pages = {20130084-20130084},
  abstract = {{What kind of environment may exist on terrestrial planets around other
stars? In spite of the lack of direct observations, it may not be
premature to speculate on exoplanetary climates, for instance to
optimize future telescopic observations, or to assess the probability of
habitable worlds. To first order, climate primarily depends on 1) The
atmospheric composition and the volatile inventory; 2) The incident
stellar flux; 3) The tidal evolution of the planetary spin, which can
notably lock a planet with a permanent night side. The atmospheric
composition and mass depends on complex processes which are difficult to
model: origins of volatile, atmospheric escape, geochemistry,
photochemistry. We discuss physical constraints which can help us to
speculate on the possible type of atmosphere, depending on the planet
size, its final distance for its star and the star type. Assuming that
the atmosphere is known, the possible climates can be explored using
Global Climate Models analogous to the ones developed to simulate the
Earth as well as the other telluric atmospheres in the solar system. Our
experience with Mars, Titan and Venus suggests that realistic climate
simulators can be developed by combining components like a ``dynamical
core'', a radiative transfer solver, a parametrisation of subgrid-scale
turbulence and convection, a thermal ground model, and a volatile phase
change code. On this basis, we can aspire to build reliable climate
predictors for exoplanets. However, whatever the accuracy of the models,
predicting the actual climate regime on a specific planet will remain
challenging because climate systems are affected by strong positive
destabilizing feedbacks (such as runaway glaciations and runaway
greenhouse effect). They can drive planets with very similar forcing and
volatile inventory to completely different states.
  doi = {10.1098/rsta.2013.0084},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lauritzen}, P.~H. and {Bacmeister}, J.~T. and {Dubos}, T. and 
	{Lebonnois}, S. and {Taylor}, M.~A.},
  title = {{Held-Suarez simulations with the Community Atmosphere Model Spectral Element (CAM-SE) dynamical core: A global axial angular momentum analysis using Eulerian and floating Lagrangian vertical coordinates}},
  journal = {Journal of Advances in Modeling Earth Systems},
  keywords = {angular momentum, vertical discretization, spectral elements, Galerkin methods, hyperviscosity, dynamical core},
  year = 2014,
  volume = 6,
  pages = {129-140},
  abstract = {{In this paper, an analysis of the global AAM conservation properties of
NCAR's Community Atmosphere Model Spectral Element (CAM-SE) dynamical
core under Held-Suarez forcing is presented. It is shown that the
spurious sources/sinks of AAM in CAM-SE are 3 orders of magnitude
smaller than the parameterized (physical) sources/sinks. The effect on
AAM conservation by changing various numerical aspects of the dynamical
core (e.g., different vertical coordinates, reduced formal order of
accuracy, increased dissipation, and decreased divergence damping) is
investigated. In particular, it is noted that changing from Eulerian
(hybrid-sigma) to floating Lagrangian vertical coordinates does not
alter the global AAM conservation properties of CAM-SE.
  doi = {10.1002/2013MS000268},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Samuel}, B. and {Leconte}, J. and {Rouan}, D. and {Forget}, F. and 
	{Léger}, A. and {Schneider}, J.},
  title = {{Constraining physics of very hot super-Earths with the James Webb Telescope. The case of CoRot-7b}},
  journal = {\aap},
  archiveprefix = {arXiv},
  eprint = {1402.6637},
  primaryclass = {astro-ph.EP},
  keywords = {planets and satellites: atmospheres, planet-star interactions, planets and satellites: physical evolution, planets and satellites: fundamental parameters, planets and satellites: composition, planets and satellites: surfaces},
  year = 2014,
  volume = 563,
  eid = {A103},
  pages = {A103},
  abstract = {{Context. Transit detection from space using ultra-precise photometry led
to the first detection of super-Earths with solid surfaces: CoRot-7b and
Kepler-10b. Because they lie only a few stellar radii from their host
stars, these two rocky planets are expected to be extremely hot. 
Aims: Assuming that these planets are in a synchronous rotation state and receive strong stellar winds and fluxes, previous studies have suggested that they must be atmosphere-free and that a lava ocean is present on their hot dayside. In this article, we use several dedicated thermal models of the irradiated planet to study how observations with NIRSPEC on the James Webb Space Telescope (JWST) could further confirm and constrain, or reject the atmosphere-free lava ocean planet model for very hot super-Earths.
Methods: Using CoRoT-7b as a working case, we explore the consequences on the phase-curve of a non tidal-locked rotation, with the presence/absence of an atmosphere, and for different values of the surface albedo. We then simulate future observations of the reflected light and thermal emission from CoRoT-7b with NIRSPEC-JWST and look for detectable signatures, such as time lag, of those peculiarities. We also study the possibility to retrieve the latitudinal surface temperature distribution from the observed SED.
Results: We demonstrate that we should be able to constrain several parameters after observations of two orbits (42 h) thanks to the broad range of wavelengths accessible with JWST: i) the Bond albedo is retrieved to within {\plusmn}0.03 in most cases. ii) The lag effect allows us to retrieve the rotation period within 3 h of a non phase-locked planet, whose rotation would be half the orbital period; for longer period, the accuracy is reduced. iii) Any spin period shorter than a limit in the range 30-800 h, depending on the thickness of the thermal layer in the soil, would be detected. iv) The presence of a thick gray atmosphere with a pressure of one bar, and a specific opacity higher than 10$^{-5}$ m$^{-2}$ kg$^{-1}$ is detectable. v) With spectra up to 4.5 {$\mu$}m, the latitudinal temperature profile can be retrieved to within 30 K with a risk of a totally wrong solution in 5\% of the cases. This last result is obtained for a signal-to-noise ratio around 5 per resel, which should be reached on Corot-7 after a total exposure time of \~{}70 h with NIRSPEC and only three hours on a V = 8 star.
Conclusions: We conclude that it should thus be possible to distinguish the reference situation of a lava ocean with phase-locking and no atmosphere from other cases. In addition, obtaining the surface temperature map and the albedo brings important constraints on the nature or the physical state of the soil of hot super-Earths. }}, doi = {10.1051/0004-6361/201321039}, adsurl = {}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }
  author = {{Hartmann}, W.~K. and {Ansan}, V. and {Berman}, D.~C. and {Mangold}, N. and 
	{Forget}, F.},
  title = {{Comprehensive analysis of glaciated martian crater Greg}},
  journal = {\icarus},
  year = 2014,
  volume = 228,
  pages = {96-120},
  abstract = {{The 66-km diameter martian crater, Greg, east of Hellas, hosts various
distinctive features, including dendritic valleys filled with
chevron-textured masses (south wall), and lobate tongues a few
kilometers long (north wall). We analyze these features by various
quantitative techniques to illuminate martian geologic and climatic
history. Crater retention model ages indicate that Greg is at least
1-3 Gy old, but surface layers of mantles and glacial features are
orders of magnitude younger. Properties of the dendritic valleys,
combined with climate models, suggest that fluvial activity began under
a thicker, warmer atmosphere, soon after the crater's formation. The
oldest exposed fluvial systems have surface crater retention ages of a
few hundred My, indicating runoff in recent geologic time. Much of Greg
is covered by ice-rich mantle deposits, for which we infer gradual
accumulation and depths of order 30-85 m; they mask pre-existing
landforms. The lobate tongues are interpreted as glaciers with mean
slope of 10.2 {\plusmn} 2.3{\deg} and average thickness of 33 {\plusmn} 19
m. Our calculations and data suggest that these glaciers were originally
ice-rich and that their surface layers have been depleted by volatile
loss. The glaciers probably formed when ice-rich mantle deposits reached
critical thickness and flowed downhill. The top 5-10 m of the
mantle and glaciers show crater survival times of order a few My to
{\tilde}15 My, which, remarkably, is the time since the last 1-4
episodes of obliquity $\gt$45{\deg}. Global climate models affirm that
Greg lies in one of two non-polar areas with extremes of ice deposition
during high-obliquity epochs. This match with observations supports the
use of such models in studies of planetary climate change.
  doi = {10.1016/j.icarus.2013.09.016},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Reiss}, D. and {Spiga}, A. and {Erkeling}, G.},
  title = {{The horizontal motion of dust devils on Mars derived from CRISM and CTX/HiRISE observations}},
  journal = {\icarus},
  year = 2014,
  volume = 227,
  pages = {8-20},
  abstract = {{We derived the horizontal motion (speed and direction) of dust devils
from time-delayed Mars Reconnaissance Orbiter (MRO) coordinated image
data sets of the Compact Reconnaissance Imaging Spectrometer for Mars
(CRISM) to the Context Camera (CTX) and/or the High Resolution Imaging
Science Experiment (HiRISE) acquired between 2008 and 2011. In total, 47
dust devils were observed in 15 regions with diameters ranging from 15
to 280 m with an average diameter of 100 m and heights from 40 to 4400
m. Horizontal speeds of 44 dust devils range from 4 to 25
ms$^{-1}$ with average speeds of 12 ms$^{-1}$.
The majority of dust devils were observed in the northern hemisphere
(79\%), mainly in Amazonis Planitia (67.5\% from the northern hemisphere
dust devils). Seasonal occurrence of dust devils in the northern
hemisphere is predominant in early and mid spring (76\%). We compared our
measured dust devil horizontal speeds and directions of motion to the
Climate Database (MCD) derived from General Circulation Model (GCM)
predictions. There is a broad agreement between dust devil horizontal
speeds and MCD wind speed predictions within the Planetary Boundary
Layer (PBL) as well as dust devil directions of motion and MCD predicted
wind directions occurring within the PBL. Comparisons between dust devil
horizontal speeds and MCD near-surface wind speed predictions at 10 m
height above the surface do not correlate well: dust devils move about a
factor of 2 faster than MCD near-surface wind predictions. The largest
offsets between dust devil motion and MCD predictions were related to
three dust devils occurring near the Phoenix landing site when the
lander was still active. The offsets could be explained by a regional
weather front passing over the Phoenix landing site. In general, the
good agreement between dust devil horizontal speeds and directions of
motion, and ambient wind speeds and directions predicted within the PBL
through GCM, show that dust devils on Mars move with ambient winds in
the PBL, hence faster than near surface winds.
  doi = {10.1016/j.icarus.2013.08.028},
  adsurl = {},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}