Mars' polar layered deposits (PLD) are comprised of layers of varying dust-to-water ice volume mixing ratios (VMR) that may record astronomically-forced climatic variation over Mars' recent orbital history. Retracing the formation of these layers by quantifying the sensitivity of deposition rates of polar material to astronomical forcing is critical for the interpretation of this record. Using a Mars global climate model (GCM), we investigate the sensitivity of annual polar water ice and dust surface deposition to various obliquities and surface water ice distributions at zero eccentricity, providing a reasonable characterization of the evolution of the PLD during recent low-eccentricity epochs. For obliquities between 15° - 35°, predicted net annual accumulation rates range from -1 to +14 mm/yr for water ice and from +0.003 to +0.3 mm/yr for dust. GCM-derived rates are ingested into an integration model that simulates polar accumulation of water ice and dust over 5 consecutive obliquity cycles (~700 kyrs) during a low eccentricity epoch. A subset of integration simulations predict combined accumulation of water ice and dust in the north at time averaged rates that are near the observationally-inferred value of 0.5 mm/yr. Three types of layers are produced per obliquity cycle: a ~30 m-thick dust-rich (~25% dust VMR) layer forms at high obliquity, a ~0.5 m-thick dust lag forms at low obliquity, and two ~10 m-thick dust-poor (~3%) layers form when obliquity is increasing/decreasing. The ~30 m-thick dust-rich layer is reminiscent of a ~30 m feature derived from visible imagery analysis the north PLD, while the ~0.5 m-thick dust lag is a factor of ~2 smaller than observed "thin layers". Overall, this investigation provides further evidence for obliquity forcing in the PLD climate record, and demonstrates the importance of ice-on-dust nucleation in polar depositional processes.
We performed numerical simulations of the obliquity evolution of Mars during the Noachian era, at which time the giant planets were on drastically different orbits than today. For the preferred primordial configuration of the planets we find that there are two large zones where the Martian obliquity is stable and oscillates with an amplitude lower than 20$^\circ$. These zones occur at obliquities below 30$^\circ$ and above 60$^\circ$; intermediate values show either resonant or chaotic behaviour depending on the primordial orbits of the terrestrial planets.
The Martian obliquity cycle is predominately influenced by Solar and Jovian tidal forces. The present-day axial tilt of Mars (25 degrees) is predicted to cycle between 0 degrees and 60 degrees (Mischna & Richardson 2005) with excursions up to 80 degrees(Laskar et al. 2004). We focused on Arabia Terra, a region especially well-suited for studying glacial migration due to its location in the northern mid-latitude (20-40 degrees North, 0-30 degrees East) zone, and its heavily cratered terrain. We created glacial and fluvial morphology distribution maps with the ESRI Aeronautical Reconnaissance Co…
We use observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of the north polar cap during late summer for two Martian years, to monitor the complete summer cycle of albedo and water ice grain size in order to place quantitative limits of the amount of water ice deposited in late summer. We establish here for the first time the complete spring to summer cycle of water ice grain sizes on the north polar cap. The apparent grain sizes grow until Ls=132, when they appear to shrink again, until they are obscured at the end of summer by the north polar hood. Under the as…
The spectral signature of water ice was observed on Martian south polar cap in 2004 by the Observatoire pour l'Mineralogie, l'Eau les Glaces et l'Activite (OMEGA) (Bibring et al., 2004). Three years later, the OMEGA instrument was used to discover water ice deposited during southern summer on the polar cap (Langevin et al., 2007). However, temporal and spatial variations of these water ice signatures have remained unexplored, and the origins of these water deposits remains an important scientific question. To investigate this question, we have used observations from the Compact Reconnaissance …
Mars' transition from an early "warm and wet" to the "cold and dry" environment left fingerprints on the geological record of fluvial activity on Mars. The morphological and mineralogical observations of aqueous activity provided varying constraints on the condition and duration of liquid water on martian surface. In this study, we surveyed the mineralogy of martian alluvial fans and deltas and investigated the hydrated silica-bearing deposits associated with these landforms. Using CRISM data, we identified 35 locations across Mars with hydrated silica in proximity to fan/deltas, where the spe…
Exposed scarps images and ice-penetrating radar measurements in the North Polar Layered Deposits (NPLD) of Mars show alternating layers that provide an archive of past climate oscillations, that are thought to be linked to orbital variations, akin to Milankovitch cycles on Earth. We use the Laboratoire de Meteorologie Dynamique (LMD) Martian Global Climate Model (GCM) to study paleoclimate states to enable a better interpretation of the NPLD physical and chemical stratigraphy. When a tropical ice reservoir is present, water vapor transport from the tropics to the poles at low obliquity is modu…
The paper deals with the investigation of the Mars subsurface by means of data collected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding working at few MHz frequencies. A data processing strategy, which combines a simple inversion model and an accurate procedure for data selection is presented. This strategy permits to mitigate the theoretical and practical difficulties of the inverse problem arising because of the inaccurate knowledge of the parameters regarding both the scenario under investigation and the radiated electromagnetic field impinging on the Mars surface. The re…
On the basis of geological evidence, it is often stated that the early martian climate was warm enough for liquid water to flow on the surface thanks to the greenhouse effect of a thick atmosphere. We present 3D global climate simulations of the early martian climate performed assuming a faint young sun and a CO2 atmosphere with pressure between 0.1 and 7 bars. The model includes a detailed radiative transfer model using revised CO2 gas collision induced absorption properties, and a parameterisation of the CO2 ice cloud microphysical and radiative properties. A wide range of possible climates …
A key outstanding question in Martian science is 'are the polar caps gaining or losing mass and what are the implications for past, current and future climate?' To address this question, we use observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of the north polar cap during late summer for multiple Martian years, to monitor the summertime water cycle in order to place quantitative limits on the amount of water ice deposited and sublimed in late summer. We establish here for the first time the summer cycle of water ice absorption band signatures on the north pola…
Recent discoveries of anomalously bright radar reflections below the Mars South Polar Layered Deposit (SPLD) have sparked new speculation that liquid water may be present below the ice cap. The reflections, discovered in data acquired by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board the Mars Express orbiter, were interpreted as reflections from damp materials or even subsurface ponds and lakes similar to those found beneath Earth's ice sheets. Recent studies, however, have questioned the feasibility of melting and maintaining liquid water below the SPLD. Her…
The gullies on Mars were discovered in the year 1999.Since then several hypotheses have appeared trying to explain the presence of these gullies. The main hypotheses are the ones which suggest that some liquid, water or CO2, was responsible for modeling the gullies and ones that propose dry flows as the modeling agents. The aim of this work is to develop an alternative hypotetical mechanism of formation of Martian gullies.Our model proposes that the Martian gullies were formed as a result of a fluidization process of the material deposited on the slopes of the impact craters, plateaux and othe…
The Mars Atmosphere-Ice Coupler MAIC-2 is a simple, latitudinal model, which consists of a set of parameterisations for the surface temperature, the atmospheric water transport and the surface mass balance (condensation minus evaporation) of water ice. It is driven directly by the orbital parameters obliquity, eccentricity and solar longitude (Ls) of perihelion. Surface temperature is described by the Local Insolation Temperature (LIT) scheme, which uses a daily and latitude-dependent radiation balance. The evaporation rate of water is calculated by an expression for free convection, driven by…
CO2+H2 greenhouse warming has recently emerged as a promising scenario to sufficiently warm the early martian surface to allow the formation of valley networks and lakes. Here we present numerical 3-D global climate simulations of the early martian climate that we have performed assuming dense CO2+H2 atmospheres. Our climate model, derived from earlier works by Forget et al. (2013) and Wordsworth et al. (2013), is coupled to an asynchronous model of the long-term evolution of martian glaciers and lakes. Simulations were carried out at 40° obliquity to investigate how (i) water content and (ii)…
Bright basal reflectors in radargram from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) of the Martian south polar layered deposits (SPLD) have been interpreted to be evidence of subglacial lakes. However, this interpretation is difficult to reconcile with the low Martian geothermal heat flow and the frigid surface temperature at the south pole. We conduct a comprehensive thermophysical evolution modeling of the SPLD and show that subglacial lakes may only form under exceptional circumstances. Subglacial lakes may form if the SPLD contains more than 60 % dust volumetr…
The layered polar caps of Mars have long been thought to be related to variations in orbit and axial tilt. We dynamically link Mars's past climate variations with the stratigraphy and isotopic composition of its ice by modeling the exchange of H2O and HDO among three reservoirs. The model shows that the interplay among equatorial, mid-latitude, and north-polar layered deposits (NPLD) induces significant isotopic changes in the cap. The diffusive properties of the sublimation lags and dust content in our model result in a cap size consistent with current Mars. The layer thicknesses are mostly c…
Dark deposits visible from orbit appear in the Martian south polar region during the springtime. These are thought to form from explosive jets of carbon dioxide gas breaking through the thawing seasonal ice cap, carrying dust and dirt which is then deposited onto the ice as dark 'blotches', or blown by the surface winds into streaks or 'fans'. We investigate machine learning (ML) methods for automatically identifying these seasonal features in High Resolution Imaging Science Experiment (HiRISE) satellite imagery. We designed deep Convolutional Neural Networks (CNNs) that were trained and teste…
There is growing evidence suggesting the presence of aqueous environment on ancient Mars, raising the question of the possibility of life in such an environment. Subsequently, with the erosion of the Martian atmosphere resulting in drastic changes in its climate, surface water disappeared, shrinking habitable spaces on the planet, with only a limited amount of water remaining near the surface in form of brines and water-ice deposits. Life, if it ever existed, would have had to adapt to harsh modern conditions, which includes low temperatures and surface pressure, and high radiation dose. Prese…
Properties of Seasonal Ice at Sisyphi Cavi and Implications for Current Modification of Martian Gullies
Institut d’Astrophysique Spatiale（空间天体物理研究所）；Université Paris-Saclay（巴黎萨克雷大学）；CNRS, GEOPS（法国国家科学研究中心，地球、行星科学与宇宙学实验室）；Dept. d’Astrophysique/AIM, CEA/IRFU, CNRS/INSU（天体物理学部/天体物理学与星际介质实验室，CEA/IRFU，法国国家科学研究中心/欧洲核子研究组织）；Laboratoire d’Astrophysique de Marseille（马赛天体物理实验室）；Aix Marseille Université（艾克斯-马赛大学）；Laboratoire de Panétologie et Géosciences（泛生态学及地质科学实验室）；Université de Nantes（南特大学）；Institut Universitaire de France（法兰西学院）
The time variations of spectral properties of dark martian surface features are investigated using the OMEGA near-IR dataset. The analyzed period covers two Mars years, spanning from early 2004 to early 2008 (includes the 2007 global dust event). Radiative transfer modeling indicates that the apparent albedo variations of low to mid-latitude dark regions are consistent with those produced by the varying optical depth of atmospheric dust as measured simultaneously from the ground by the Mars Exploration Rovers. We observe only a few significant albedo changes that can be attributed to surface p…
We present a model of radiative transfer through atmospheric particles based on Monte Carlo methods. This model can be used to analyze and remove the contribution of aerosols in remote sensing observations. We have developed a method to quantify the contribution of atmospheric dust in near-IR spectra of the Martian surface obtained by the OMEGA imaging spectrometer on board Mars Express. Using observations in the nadir pointing mode with significant differences in solar incidence angles, we can infer the optical depth of atmospheric dust, and we can retrieve the surface reflectance spectra fre…
The detection of liquid water by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) at the base of the south polar layered deposits in Ultimi Scopuli has reinvigorated the debate about the origin and stability of liquid water under present-day Martian conditions. To establish the extent of subglacial water in this region, we acquired new data, achieving extended radar coverage over the study area. Here, we present and discuss the results obtained by a new method of analysis of the complete MARSIS dataset, based on signal processing procedures usually applied to terrestrial…
Remote sensing data from orbiter missions have proposed that ground ice may currently exist on Mars, although the volume is still uncertain. Recent analyses of Martian meteorites have suggested that the water reservoirs have at least three distinct hydrogen isotope compositions (D/H ratios): primordial and high D/H ratios, which are approximately the same and six times that of ocean water on Earth, respectively, and a newly identified intermediate D/H ratio, which is approximately two to three times higher than that in ocean water on Earth. We calculate the evolution of the D/H ratios and the …
The distribution of subsurface water ice on Mars is a key constraint on past climate, while the volumetric concentration of buried ice (pore-filling versus excess) provides information about the process that led to its deposition. We investigate the subsurface of Arcadia Planitia by measuring the depth of terraces in simple impact craters and mapping a widespread subsurface reflection in radar sounding data. Assuming that the contrast in material strengths responsible for the terracing is the same dielectric interface that causes the radar reflection, we can combine these data to estimate the …
The presence of liquid water at the base of the Martian polar caps has long been suspected but not observed. We surveyed the Planum Australe region using the Mars Advanced Radar for Subsurface and Ionosphere Sounding, a low-frequency radar on the Mars Express spacecraft. Radar profiles collected between May 2012 and December 2015, contain evidence of liquid water trapped below the ice of the South Polar Layered Deposits. Anomalously bright subsurface reflections were found within a well-defined, 20km wide zone centered at 193°E, 81°S, surrounded by much less reflective areas. Quantitative anal…
We present the results of a systematic mapping of seasonally sculpted terrains on the South Polar region of Mars with the Planet Four: Terrains (P4T) online citizen science project. P4T enlists members of the general public to visually identify features in the publicly released Mars Reconnaissance Orbiter CTX images. In particular, P4T volunteers are asked to identify: 1) araneiforms (including features with a central pit and radiating channels known as 'spiders'); 2) erosional depressions, troughs, mesas, ridges, and quasi-circular pits characteristic of the South Polar Residual Cap (SPRC) wh…
We present improved Mars Odyssey Neutron Spectrometer (MONS) maps of near-surface Water-Equivalent Hydrogen (WEH) on Mars that have intriguing implications for the global distribution of "excess" ice, which occurs when the mass fraction of water ice exceeds the threshold amount needed to saturate the pore volume in normal soils. We have refined the crossover technique of Feldman et al. (2011) by using spatial deconvolution and Gaussian weighting to create the first globally self-consistent map of WEH. At low latitudes, our new maps indicate that WEH exceeds 15% in several near-equatorial regio…
The Martian climate is governed by an annual cycle, that results in the condensation of CO$_{2}$ ice during winter, up to a meter thick at the pole and thousands of kilometers in extension. Water and dust may be trapped during the condensation and freed during the sublimation. In addition, ice may be translucent or granular depending on the deposition process (snow vs direct condensation), annealing efficiency, and dust sinking process. The determination of ice translucency is of particular interest to confirm or reject the cold jet model (also known as Kieffer model). This work is focused on …
