A document by Antoine Lucas. Click on the document to view its contents.

Motivation: On May 5, 2022, the martian SEIS seismometer recorded an unprecedented M Ma W 4.7 Marsquake. The epicenter is located at 3.0 • S, 171.9 • E. The areas is barely flat with only a few N-S tectonic-like features. Most unfilled impact craters and ridges show dust avalanches (a.k.a. Slope streaks). We investigate the post-seismic outcomes in terms of avalanche triggering under today's Mars conditions in the framework of the s1222a event.

One of the long-standing question in geoscience is whether there is a topographical signature of life. Recent development of space-borne LiDAR has led to massive data depicting planetary topographies, opening up unprecedented opportunities to make progress in answering this question. This is what we set out to do in an ongoing project named í µí±ƒí µí°´í µí±í µí°¾í µí°¸í µí±. A key step of PARKER is to find topograph-ical features that are potentially relevant to intrinsic differences between Earth and alien worlds. Due to the huge data volume, sequential feature extraction cannot meet our needs in PARKER. Hence, in this work we propose a GPU-accelerated framework for fast feature extraction of planetary LiDAR, which as far as we know is the first GPU-based solution for this task. Faced with multi-scale features and limited GPU memory, we present a novel pseudo-one-pass sweep (POPS) approach, leveraging memory-aware data grouping and incremental data transfer to address these challenges. We also develop a GPU-based solution to aggregate features extracted by POPS. Experiments on real and simulated data show that our algorithms are 2-3 orders of magnitude faster than their sequential counterparts and 1-2 orders of magnitude faster than MPI-based multi-core parallelism, enabling near real-time analytics of datasets with almost a billion points. Based on POPS, we have been able to efficiently evaluate the relevance of topographical features to intrinsic inter-planetary differences. So far, we have assessed the abilities of two feature extractions methods, PCA and STAT, to capture differences between Earth and Mars. Results show that PCA features on scales of 300-500m can best capture such differences. Thanks to the generic nature of POPS, we will be able to expand our studies to new feature extraction methods and other alien worlds than Mars in the next phase of PARKER.

Extreme precipitation events play a pivotal role in shaping Earth’s surface through their influences on hillslope processes and sediment transport in rivers. In this study, we focus on understanding the implications of such events on sediment transport, using Réunion Island as a natural laboratory due to its intense tropical rainfall regime. Through photogrammetric techniques and subsequent sediment volume estimates spanning decades as well as cosmogenic 3He measurements, we assessed the spatio-temporal evolution of the canyon bed of the ephemeral Rivière des Remparts and the drainage of products from major landslides and/or rock avalanches between 1950 and 2011. Results show that 39.6 Mm3 of sediment was transported out of the watershed in 62 years. Furthermore, we modeled the flow dates of this ephemeral river and show that such an export of material actually happened during only 391 days over the 62 years, at an average rate of 0.1 Mm3/day. Our investigation confirms that sediment transport coincides with officially recorded extreme meteorological events such as cyclones. Moreover, our findings reveal that sediment transport predominantly occurs on days corresponding to high-percentile rank precipitation events, demonstrating that all transport is concentrated during these intense rainfall periods. Finally, this study underscores the extremely fast conveyance of material from slopes to deep-sea fans, facilitated in Réunion by the absence of a coastal platform. This rapid transfer has implications for CO2 consumption, as it should enhance the transport and burial of organic matter particles, potentially contributing significantly to the island’s overall CO2 consumption efficiency.

A document by Antoine Lucas. Click on the document to view its contents.

A document by Antoine Lucas. Click on the document to view its contents.

In recent decades, with the placement of LiDAR remote sensing instruments in orbit, we now have global coverage of the bare-ground elevation on the Earth, Mars and beyond. Encoded in such planetary LiDAR data are interesting landscape features that promise to further our knowledge of planetary topography. However, discovery of such features entails 3 major challenges: 1) massive data; 2) the need for local multi-scale features; 3) sensitivity to interfering factors. To address these challenges, we propose FARMYARD, a generic pipeline for \underline{F}e\underline{a}ture Discove\underline{r}y Fro\underline{m} Planetar\underline{y} LiD\underline{AR} \underline{D}ata Data. To our knowledge, this is the first time such a pipeline has been proposed, which provides a brand new methodology for comparative studies of planetary topography. Specifically, drawing on the parallel computing power of the Graphics Processing Unit (GPU), we propose a novel pseudo-on-pass sweep (POPS) framework for fast and memory-efficient feature extraction for massive planetary LiDAR data, a two-level division scheme for local regions with support for multi-scale features, and a Domain-Shifted Partition (DSP) scheme for feature evaluation that is robust against interfering factors. To showcase the utility of our FARMYARD pipeline, we deploy it to a real-world research project, which seeks to find topographical signatures of life by discovering features that can potentially distinguish between the Earth and alien worlds with no known life activity. We also highlight the efficiency of our POPS framework with experiments on both synthetic and real data, which can be thousands of times faster than its CPU-based counterpart, including a multi-core parallel solution.

On the seasonal time scale, for accessible locations and when manpower is available, direct observations and field survey are the most useful and standard approaches. However very limited studies have been conducted on direct observation at the decennial to century time-scale due to observational constrains. Here, we present an open and reproducible pipeline based on historical aerial images (up to 70 yrs time span) that includes sensor calibration, dense matching and elevation reconstruction over two areas of interest that represent pristine examples for tropical and alpine environments. The Remparts Canyon and Langevin River in Reunion Island, and the Bossons glacier in the French Alps share a limited accessibility (in time and space) that can be overcome only from remote-sensing. We reach a metric to sub-metric resolution close to the nominal images spatial sampling. This provides elevation time series with a better resolution to most recent satellite images such as Pleiades over decennial time period.

The NASA InSight mission to Mars successfully landed on November 26th, 2018 in Elysium Planitia. It aims to characterize the seismic activity and constrain the internal structure of Mars. We focus on the Cerberus Fossae region, a giant fracture network of ~1200 km long situated east of the InSight landing site, and where M~3 marsquakes were detected during the past two years. It is formed of five main fossae located on the southeast of the Elysium Mons volcanic rise. We perform a detailed mapping of the entire system based on high resolution satellite images and Digital Elevation Models. The refined cartography reveals a range of morphologies associated with dike activities at depth. Width and throw measurements of the fossae are linearly correlated, suggesting a possible tectonic control on the shapes of the fossae. Widths and throws decrease toward the east, indicating the long-term direction of propagation of the dike-induced graben system. They also give insights into the geometry at depth and how the possible faults and fractures are rooted in the crust. The exceptional preservation of the fossae allows us to detect up to four scales of segmentation, each formed by a similar number of 3-4 segments/subsegments. This generic distribution is comparable to continental faults and fractures on Earth. We anticipate higher stress and potential for marsquakes within intersegment zones and at graben tips.

Orbital and surface observations demonstrate that aeolian activity is occurring on Mars. Here we report the aeolian changes observed in situ by NASA's InSight lander during the first 400 sols of operations. Aeolian changes include creep of grains with diameters of up to 3 mm, dust removal, dark trails left by passing vortices and possible saltation. InSight has observed such changes by using, for the first time, simultaneous imaging and continuous, high-frequency meteorological, seismological, and magnetic measurements. We show that this multi-instrument combination constrains both the timing, and specific atmospheric conditions during which, aeolian changes occur. The observed changes are infrequent and episodic, consistently occur between noon and 3 pm, and are systematically associated with the passage of convective vortices. The sudden onset of peak vortex wind speeds promotes particle motion during sequences of enhanced vortex activity and stronger ambient winds. Aeolian changes are correlated with excursions in ground acceleration and magnetic field strength, suggesting vortex-induced ground deformation and charged-particle motion.

Mountainous landscape evolution under tropical and alpine environments is mainly dictated by climatic forcing which influences underlying mechanisms of geomorphic transport (e.g., soil formation, river dynamics, slope stability and mass wasting). The time scale over which this influence acts ranges from seasonal to decennial time span. On the seasonal time scale, for accessible locations and when manpower is available, direct observations and field survey are the most useful and standard approaches. While very limited studies have been focused on the the decennial and century scale due to observational constrains. Here, we present an open and reproducible pipeline based on historical aerial images (up to 70yrs time span) that includes sensor calibration, dense matching and elevation reconstruction over two areas of interest that represent pristine examples for tropical and alpine environments: The Rempart Canyon in Reunion Island, and the Bossons glacier in the French Alps share a limited accessibility (in time and space) that can be overcome only from remote-sensing. We reach unprecedented resolution: the aero-triangulation falls at sub-metric scale based on ground truth, which is comparable to the initial images spatial sampling. This provides elevation time series with a better resolution to most recent satellite images such as Pleiades. In the case of the Rempart Canyon, we identified and quantified the results of 2 landslides that occurred in 1965 and 2001, and characterized the landslides dynamics. As for the alpine case, we highlight the effect of the temperature plateau occurred during 1939-1970 in Europe before the well known accelerated retreat during the post-industrial period. In both cases, we emphasize the strong effect of extreme events over multi-decennial to century time-scales.