A Passive Probe for Subsurface Oceans and Liquid Water in Jupiter's Icy Moons

We describe an interferometric reflectometer method for passive detection of subsurface oceans and liquid water in Jovian icy moons using Jupiter's decametric radio emission (DAM). The DAM flux density exceeds 3,000 times the galactic background in the neighborhood of the Jovian icy moons, providing a signal that could be used for passive radio sounding. An instrument located between the icy moon and Jupiter could sample the DAM emission along with its echoes reflected in the ice layer of the target moon. Cross-correlating the direct emission with the echoes would provide a measurement of the ice shell thickness along with its dielectric properties. The interferometric reflectometer provides a simple solution to sub-Jovian radio sounding of ice shells that is complementary to ice penetrating radar measurements better suited to measurements in the anti-Jovian hemisphere that shadows Jupiter's strong decametric emission. The passive nature of this technique also serves as risk reduction in case of radar transmitter failure. The interferometric reflectometer could operate with electrically short antennas, thus extending ice depth measurements to lower frequencies, and potentially providing a deeper view into the ice shells of Jovian moons.Comment: Submitted to Icaru

Potentiel du radar de pénétration du sol pour la caractérisation de la nappe phréatique peu profonde dans la région de Mnasra au Maroc

Morocco is a water-scarce country confronted with a severe dependence on rain-fed agriculture and dwindling groundwater reserves. Since 1995, new water regulation laws and management strategies have been promulgated providing a comprehensive framework for an integrated management. Moreover, water managers should have precise data on the current state of water tables depth in strategic aquifers. Unfortunately, the main source of these data are sporadic wells with no automated monitoring systems making the assessment of  water table dynamics, costly, time consuming and out-phased with decision maker needs. In this respect, this paper focuses on the capability of Ground Penetrating Radar to determine the depth of shallow water table in Mnasra region, located in the Gharb region of Morocco as a pilot study to generalize its use in the future for groundwater dynamic monitoring purposes in Morocco. The experiment was undertaken using Mala 800 MHz shielded antennas and was able to probe the depth of the upper fresh water table at 3.75 m deep in the Mnasra aquifer in semi-arid conditions. Data collected by GPR can be used as substitute for well logs to enhance the monitoring of water tables in stressed areas during droughts and excessive recharges during rainy season. Keywords : Ground Penetrating Radar, Shallow water table, Mnasra, Gharb Region, Mala 800 Mhz Antenna, Monitoring of water table.  Le Maroc est un pays à ressources en eau limitées confronté à une dépendance à l’agriculture pluviale et une diminution des réserves des eaux souterraines. Depuis 1995, de nouvelles lois de règlementation d’eau et des stratégies de gestion ont été promulguées fournissant un cadre global de gestion intégrée. Par ailleurs, les gestionnaires doivent disposer de données précises et actualisées sur le niveau des nappes stratégiques. Malheureusement, la principale source des données est celle des puits sporadiques sans systèmes de suivi automatisés rendant l’évaluation des dynamiques des nappes coûteuse, exigeante en temps et en déphasage avec les besoins des décideurs. Ainsi, cet article se focalise sur la capacité des sondeurs radar (GPR) à déterminer la profondeur de la nappe souterraine de Mnasra, zone pilote située dans la région du Gharb au Maroc pour généraliser son utilisation dans le suivi des nappes au Maroc. Il était possible de sonder, en utilisant des antennes Mala 800 MHz, le niveau de la nappe à une profondeur de 3.75 m dans des conditions semi-arides. Les données GPR collectées peuvent être utilisées comme substitut des puits pour rehausser le suivi des nappes dans les zones arides pendant les périodes de sécheresse et de recharge intense. Mots-clés : Sondeur Radar, nappe non profonde, Mnasra, Région de Gharb, Antenne Mala 800 Mhz, suivi des nappe

An Extended Field of Crater Structures in Egypt: Observations and Hypotheses

We detected more than 1000 crater structures in the Western Egyptian Desert, distributed over 40000 km2, among which 62 were studied on the field. Two hypotheses are proposed for their origin: hydrothermal vent complexes or impact craters generated by a rubble-pile asteroid

Potentiel du radar de pénétration du sol pour la caractérisation de la nappe phréatique peu profonde dans la région de Mnasra au Maroc

Morocco is a water-scarce country confronted with a severe dependence on rain-fed agriculture and dwindling groundwater reserves. Since 1995, new water regulation laws and management strategies have been promulgated providing a comprehensive framework for an integrated management. Moreover, water managers should have precise data on the current state of water tables depth in strategic aquifers. Unfortunately, the main source of these data are sporadic wells with no automated monitoring systems making the assessment of  water table dynamics, costly, time consuming and out-phased with decision maker needs. In this respect, this paper focuses on the capability of Ground Penetrating Radar to determine the depth of shallow water table in Mnasra region, located in the Gharb region of Morocco as a pilot study to generalize its use in the future for groundwater dynamic monitoring purposes in Morocco. The experiment was undertaken using Mala 800 MHz shielded antennas and was able to probe the depth of the upper fresh water table at 3.75 m deep in the Mnasra aquifer in semi-arid conditions. Data collected by GPR can be used as substitute for well logs to enhance the monitoring of water tables in stressed areas during droughts and excessive recharges during rainy season. Keywords : Ground Penetrating Radar, Shallow water table, Mnasra, Gharb Region, Mala 800 Mhz Antenna, Monitoring of water table.  Le Maroc est un pays à ressources en eau limitées confronté à une dépendance à l’agriculture pluviale et une diminution des réserves des eaux souterraines. Depuis 1995, de nouvelles lois de règlementation d’eau et des stratégies de gestion ont été promulguées fournissant un cadre global de gestion intégrée. Par ailleurs, les gestionnaires doivent disposer de données précises et actualisées sur le niveau des nappes stratégiques. Malheureusement, la principale source des données est celle des puits sporadiques sans systèmes de suivi automatisés rendant l’évaluation des dynamiques des nappes coûteuse, exigeante en temps et en déphasage avec les besoins des décideurs. Ainsi, cet article se focalise sur la capacité des sondeurs radar (GPR) à déterminer la profondeur de la nappe souterraine de Mnasra, zone pilote située dans la région du Gharb au Maroc pour généraliser son utilisation dans le suivi des nappes au Maroc. Il était possible de sonder, en utilisant des antennes Mala 800 MHz, le niveau de la nappe à une profondeur de 3.75 m dans des conditions semi-arides. Les données GPR collectées peuvent être utilisées comme substitut des puits pour rehausser le suivi des nappes dans les zones arides pendant les périodes de sécheresse et de recharge intense. Mots-clés : Sondeur Radar, nappe non profonde, Mnasra, Région de Gharb, Antenne Mala 800 Mhz, suivi des nappe

Comparing dune migration measured from remote sensing with sand flux prediction based on weather data and model, a test case in Qatar

This study explores validating and calibrating the wind regime predicted by Global Circulation Models (GCM) on Earth and other planets using optical remote sensing of dune dynamics. We use Spot-5 images to track the migration of 64 Barchan dunes in Qatar using the COSI-Corr technique. We estimate the volume of the dunes using a scaling law calibrated from one particular dune, which was surveyed in the field. Using volume and migration rate, we determine the sand flux from a single dune, Q_(Dunes), and scale this estimate to the whole dune field. We compare the measured sand flux with those derived from wind velocity measurements at a local meteorological station as well as with those predicted from ERA-Interim (a Global Circulation Model). The comparison revealed that the wind velocity predicted by ERA-Interim is inappropriate to calculate the sand flux. This is due to the 6-h sampling rate and to systematic bias revealed by a comparison with the local wind data. We describe a simple procedure to correct for these effects. With the proposed correction, similar sand flux are predicted using the local and ERA-Interim data, independently of the value of the value of the shear velocity threshold, u_(*t). The predicted sand flux is about 65% of Q_(Dunes). The agreement is best assuming the value u_(*t)=0.244 m/s, which is only slightly larger than the value of u_(*t)=0.2612 m/s estimated based in the sand granulometry measured from field samples. The influence of the dune topography on the wind velocity field could explain the underestimation. In any case, the study demonstrates the possibility of validating GCM model and calibrating aeolian sand transport laws using remote sensing measurements of dune dynamics and highlights the caveats associated to such an approach

Hydrometeorology: Review of Past, Present and Future Observation Methods

Hydrometeorology aims at measuring and understanding the physics, chemistry, energy and water fluxes of the atmosphere, and their coupling with the earth surface environmental parameters. Accurate hydrometeorological records and observations with different timelines are crucial to assess climate evolution and weather forecast. Historical records suggest that the first hydrometeorological observations date back to ca 3500 BC. Reviewing these observations in the light of our modern knowledge of the dynamic of atmospheres is critical as it can reduce the ambiguities associated to understanding major fluctuations or evolutions in the earth climate. Today, the ambiguities in hydrometeorological observations have significantly improved due to the advances in monitoring, modeling, and forecasting of processes related to the land-atmosphere coupling and forcing. Numerical models have been developed to forecast hydrometeorological phenomena in short-, medium- and long-term horizons, ranging from hourly to annual timescales. We provide herein a synthetic review of advances in hydrometeorological observations from their infancy to today. In particular, we discuss the role of hydrometeorological records, observations, and modeling in assessing the amplitude and time-scale for climate change and global warming

Decline in Iran’s groundwater recharge

Groundwater recharge feeds aquifers supplying fresh-water to a population over 80 million in Iran—a global hotspot for groundwater depletion. Using an extended database comprising abstractions from over one million groundwater wells, springs, and qanats, from 2002 to 2017, here we show a significant decline of around −3.8 mm/yr in the nationwide groundwater recharge. This decline is primarily attributed to unsustainable water and environmental resources management, exacerbated by decadal changes in climatic conditions. However, it is important to note that the former’s contribution outweighs the latter. Our results show the average annual amount of nationwide groundwater recharge (i.e., ~40 mm/yr) is more than the reported average annual runoff in Iran (i.e., ~32 mm/yr), suggesting the surface water is the main contributor to groundwater recharge. Such a decline in groundwater recharge could further exacerbate the already dire aquifer depletion situation in Iran, with devastating consequences for the country’s natural environment and socio-economic development

The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling

The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples

Robotic Follow-Up for Human Exploration

We are studying how "robotic follow-up" can improve future planetary exploration. Robotic follow-up, which we define as augmenting human field work with subsequent robot activity, is a field exploration technique designed to increase human productivity and science return. To better understand the benefits, requirements, limitations and risks associated with this technique, we are conducting analog field tests with human and robot teams at the Haughton Crater impact structure on Devon Island, Canada. In this paper, we discuss the motivation for robotic follow-up, describe the scientific context and system design for our work, and present results and lessons learned from field testing