Antoine Séjourné

University of Paris-Saclay · Geosciences

This paper presents results on testing polydisperse melamine material versus sand for laboratory ice-rich layered soil system under thawing conditions. We demonstrate the potential of using polydisperse melamine particles in the aim of mimicking the permafrost geomorphological degradations and landslide found in periglacial field environments. We s...

Located in a poorly studied zone of the rear arc in the Transitional Southern Volcanic Zone, the Overo volcano presents a complete record of syn-glacial, inter-glacial, and post-glacial activity, marked by significant changes in eruptive mechanisms over time. Following pre-glacial units, an effusive syn-glacial basaltic phase was succeeded by an ex...

In evaluating the unique geomorphology of Hebrus Valles on Mars, an outflow channel southeast of Utopia Planitia, we investigated the role of fluvial dynamics in forming subsurface conduits. Unlike typical Martian channels that terminate under younger sediment rocks, Hebrus Valles retains its downstream features, thus offering a window into surface...

In the Arctic, thawing of ice-rich Yedoma permafrost has geomorphological and geochemical consequences. Carbon initially stored in permafrost, could be reintroduced in the active carbon cycle. This study aimed at identifying the origin of dissolved organic carbon (DOC) and particulate organic carbon (POC) of thermokarst lakes in Central Yakutia (Ea...

Widespread ice-rich Yedoma permafrost is known to store an important amount of carbon whose liberation will have a positive feedback on climate. Even though it covers only 1% of the permafrost area, its characteristics are diverse and studying its impacts due to thermokarst in different regions is needed. This study aims at identifying the biogeoch...

Arctic regions are highly impacted by the global temperature rising and its consequences and influences on the thermo-hydro processes and their feedbacks. Theses processes are especially not very well understood in the context of river–permafrost interactions and permafrost degradation. This paper focuses on the thermal characterization of a river–...

The current rate and magnitude of temperature rise in the Arctic are disproportionately high compared to global averages. Along with other natural and anthropogenic disturbances, this warming has caused widespread permafrost degradation and soil subsidence, resulting in the formation of thermokarst (thaw) lakes in areas of ice-rich permafrost. Thes...

Rapid permafrost degradation is observed in northern regions as a result of climate change and expanding economic development. Associated increases in active layer depth lead to thermokarst development, resulting in irregular surface topography. In Central Yakutia, significant areas of the land surface have been deteriorated by thermokarst; however...

Aims. The nucleus of comet 67P/Churyumov-Gerasimenko (67P) is ice rich and shows evidence of morphologies driven by sublimation processes. In particular, the fine-particle deposits (FPD) that cover its surface reveal depressions of many tens of meters. A detailed analysis of these morphologies and of the properties of the fine-particle deposits cou...

What was the nature of the Late Hesperian climate, warm and wet or cold and dry? Formulated this way the question leads to an apparent paradox since both options seem implausible. A warm and wet climate would have produced extensive fluvial erosion but few valley networks have been observed at the age of the Late Hesperian. A too cold climate would...

Recent evidence has shown that Arctic regions have warmed about twice as much as elsewhere on the planet over the last few decades, and that high-latitude permafrost–periglacial processes and hydrological systems are notably responsive to rising temperatures. The aim of this paper is to report on the thermal regime of islands located along the Lena...

Morphometrical comparative analysis of sublimation-shaped depressions on 67P's surface.

This volume represents the proceedings of the homonymous international conference on all aspects of impact cratering and planetary science, which was held in October 2019 in Brasília, Brazil. This volume contains a sizable suite of contributions dealing with regional impact records (Australia, Sweden), impact craters and impactites, early Archean i...

The Rosetta mission provided us with detailed data of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko.In order to better understand the physical processes associated with the comet activity and the surface evolution of its nucleus, we performed a detailed comparative morphometrical analysis of two depressions located in the Ash region...

Aims. The Rosetta mission provided us with detailed data of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko. In order to better understand the physical processes associated with the comet activity and the surface evolution of its nucleus, we performed a detailed comparative morphometrical analysis of two depressions located in the Ash...

In the ice-rich permafrost of the Arctic regions, thermokarst erosion on slopes induces the formation of large-scale retrogressive thaw slumps (RTS). They have significant geomorphological, hydrological, and biogeochemical impacts on the landscape. Further research is thus needed to better understand the respective effect of ice content and permafr...

In the ice‐rich permafrost area of Central Yakutia (Eastern Siberia, Russia), climate warming and other natural and anthropogenic disturbances have caused permafrost degradation and soil subsidence, resulting in the formation of numerous thermokarst (thaw) lakes. These lakes are hotspots of greenhouse gas emissions, but with substantial spatial and...

Thumbprint terrain was first recognized in Viking Orbiter data and described as sets of alternating continuous parallel ridges and depressions up to several tens of kilometres in length, with high and low albedo respectively. We performed a geomorphological analysis of these features using both Context Camera and High Resolution Imaging Science Exp...

The global-scale crustal structure of Mars is shaped by impact basins, volcanic provinces, and a hemispheric dichotomy with a thin crust beneath the northern lowlands and a thick crust beneath the southern highlands. The southern highlands are commonly treated as a coherent terrain of ancient crust with a common origin and shared geologic history,...

tIn a previous study, we demonstrated with a comparative morphometrical analysis the first morpho-metric evidence of a glacial landscape composed of glacial cirques and glacial valleys in the south ofTerra Sabaea at an elevation > 1000 m in two impact craters and one mountain. The purpose of this studyis to use the same method to seek other geomorp...

Recent research suggests that major meteorite impact events into a Late Hesperian/Early Amazonian ocean likely produced a mega‐tsunami that would have resurfaced coastal areas in northwestern Arabia Terra. The orientations of the associated lobate deposits, a conspicuous type of landforms called Thumbprint Terrain, suggests that if an impact event...

The climate of early Mars remains unclear and the debate is topical. Recently, climatic models have suggested a cold climate during the Noachian/ Early Hesperian on Mars, which goes against the wet and warm climate often put forward. The purpose of this study is to seek geomorphologic evidence of this early cold climate. To achieve this, a step-by-...

Martian gullies have been widely studied, but their formation mechanism is still under debate. Their channels generally trend straight downslope, but some display sinuosity. Seasonally active gullies are common on sand dunes and their channels have been reported to develop sinuosity. Here, we perform a detailed analysis of a gully on a dune within...

We used a grid‐mapping technique to analyze the distribution of 13 water‐ and ice‐related landforms in Acidalia Planitia as part of a joint effort to study the three main basins in the northern lowlands of Mars, that is, Acidalia, Utopia, and Arcadia Planitiae. The landforms were mapped at full Context Camera resolution along a 300‐km‐wide strip fr...

This work in Utopia Planitia is the first continuous regional mapping of ice‐related landforms integrated into an effort to study the three main basins (Arcadia, Acidalia, and Utopia Planitiae) in the northern plains. The distribution and morphotypes of these landforms, SHAllow RADar detections, and crater size‐frequency distribution measurements (...

A project of mapping ice‐related landforms was undertaken to understand the role of subsurface ice in the northern plains. This work is the first continuous regional mapping from CTX (ConTeXt Camera, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centered on the 170°W line of long...

We present a new research project related to permafrost and greenhouse gas (GHG) dynamics in Central Yakutia (Siberia). The main goal is to quantify fluxes, sources and ages of GHGs emitted from aquatic systems in response to permafrost degradation. We highlight five interconnected research axes, each defining a related ‘work package’ (WP). In addi...

The thermal imprint of a typical river in the continuous permafrost of Central Yakutia (Siberia, Russia) is studied by active layer thickness measurements along six cross sections, either directly or with geophysical methods. Ground-Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) measurements provide permafrost depths comparable...

We report on the detection and characterization of more than 6300 polygons on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera onboard Rosetta between August 2014 and March 2015. They are found in consolidated terrains and grouped in localized networks. They are present at all latitudes (from...

The increased volume, spatial resolution, and areal coverage of high-resolution images of Mars over the past 15 years have led to an increased quantity and variety of small-scale landform identifications. Though many such landforms are too small to represent individually on regional-scale maps, determining their presence or absence across large are...

The identification of lobate debris deposits in Arabia Terra, along the proposed paleoshoreline of a former northern ocean, has renewed questions about the existence and stability of ocean-sized body of water in the early geologic history of Mars. The potential occurrence of impact-generated tsunamis in a northern ocean was investigated by comparin...

The large size and complexity of planetary data acquired by spacecraft during the last two decades create a demand within the planetary community for access to the archives of raw and high level data and for the tools necessary to analyze these data. Among the different targets of the Solar System, Mars is unique as the combined datasets from the V...

The present day evolution of this spectacular meandering gully is formed following three different phases: 1) Sand material accumulation (not seasonal) occurred on the alcove. 2) Seasonal frost deposits, composed of CO2 and water, can be observed on pole facing slopes in autumn and winter. 3) Sudden defrost-ing of seasonal deposits during the middl...

The present day evolution of this spectacular meandering gully is formed following three different phases: 1) Sand material accumulation (not seasonal) occurred on the alcove. 2) Seasonal frost deposits, composed of CO2 and water, can be observed on pole facing slopes in autumn and winter. 3) Sudden defrost-ing of seasonal deposits during the middl...

During the past 15 years, evidence for an ice-rich planet Mars has rapidly mounted, become increasingly varied in terms of types of deposits and types of observational data, and has become more widespread across the surface. The mid-latitudes of Mars, especially Utopia Planitia, show many types of interesting landforms similar to those in periglaci...

Since their first observation by Malin and Edgett (2000) [1], martian gullies have been abundantly studied, but their formation mechanism is still under debate [e.g. 2, 3, 4, 5, 6]. Gullies are generally composed of an alcove, a channel and an apron [1, 7] and some of them are active today [8]. Here, we present our study of one specific gully, whic...

The Tharsis region is the largest volcanic complex on Mars and in the Solar System. Young lava flows cover its surface (from the Amazonian period, less than 3 billion years ago) but its growth started during the Noachian era (more than 3.7 billion years ago). Its position has induced a reorientation of the planet with respect to its spin axis (true...

As observed in most regions in the Arctic, the thawing of ice-rich permafrost (thermokarst) has been developing in Central Yakutia. However, the relationship between thermokarst development and climate variations is not well understood in this region, in particular the development rate of thaw slumps. The objective of this paper is to understand th...

Introduction: Many young landforms in mid-and high-latitudes on Mars are thought to be related to ice [1], but their exact distribution and origin are still poorly understood. In an attempt to determine their extent and identify possible spatial relationships and genetic links between them, we mapped their distribution across a N-S traverse across...

This study is part of the activities of an ISSI International Team, which intends to produce new geomorphological maps of the northern lowlands of Mars along three long traverses across Acidalia, Utopia, and Arcadia Planitiae [1]. We aim at identifying the evolutionary history and the stratigraphy of sediments and other material and their relation...

Grid mapping provides a new, efficient and scalable approach to collecting data on large quantities of small landforms over large areas.

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Introduction: In our recent study of mid Utopia Planitia (UP; ~30-60 0 N; Fig. 1) [1-3] we used all rele-vant HiRISE (High Resolution Imaging Science Ex-periment), MOC (Mars Orbiter Camera), THEMIS (Thermal Emission Imaging System) and CTX (Con-text Camera) to map a spatial assemblage of putatitive periglacial landforms (PPLs): flat-floored and sca...

About 50 locations ('cold spots') where permafrost (Arctic and Antarctic) in situ monitoring has been taking place for many years or where field stations are currently established (through, for example the Canadian ADAPT program) have been identified. These sites have been proposed to WMO Polar Space Task Group as focus areas for future monitoring...

On Earth, permafrost containing a high ice volume (referred as ice-rich) are sensible to climate change, they have been regionally degraded (thermokarst) during the early Holocene climatic optimum forming numerous thermokarst lakes in Central Yakutia (eastern Siberia). Recent temperature increases in the Arctic and Subarctic have been significantly...

Flat-floored depressions with scalloped-shapes and spatially associated small-sized polygons (diameter <∼100 m) dot the landscape of western Utopia Planitia (centered at 45°N–95°E). The scalloped depressions are thought to be the result of ice-rich regolith undergoing degradation by sublimation or thaw. Current models suggest that the formation and...

Abrupt climate-changes in the periglacial environments on Earth such as Central Yakutia (Siberia) deeply modified the landscape. This region is underlined by a continuous permafrost that is ice-rich, ~40-80% of ice by volume. The permafrost was formed during the last Pleistocene glaciation. A unique assemblage of landforms is observed: ice-wedge po...