Stochastic hyperbola fitting, probabilistic inversion, reverse-time migration and clustering: A novel interpretation toolbox for in-situ planetary radar

Ground-penetrating radar (GPR) is becoming a mainstream tool in planetary exploration, and one of the few in-situ planetary geophysical methods. There are currently three missions (Perseverance, Tianwen-1, Chang'E-4) with GPR-equipped rovers, and two future missions (Chang'E-7, ExoMars) that will include GPR in their scientific payload. The large number of GPR data, combined with the novel setup of the measurements, creates the need for new data processing and interpretation techniques to address the unique challenges of in-situ planetary radar. The current paper proposes an interpretation pipeline that starts with a novel stochastic hyperbola fitting that estimates the probability kernel density of the bulk permittivity at different depths. Subsequently, the bulk permittivity distribution is transformed via a novel probabilistic inversion to a 1-dimensional (1D) permittivity profile. The inverted 1D permittivity profile is then used as an input to a bespoke reverse-time migration (RTM) using the finite-difference time-domain (FDTD) method. RTM using FDTD does not assume a clinical homogeneous half-space; instead, it accounts for the expected layered structure of the investigated medium. Lastly, the migrated radargram is clustered in order to identify subsurface targets and distinguish them from the background medium. Each of the processing steps has never been reported in planetary radar; and together act as a complete processing toolbox tuned for planetary science. The suggested interpretation pipeline is validated numerically in a 1D case study with a complex layered structure and multiple subsurface targets. The proposed processing scheme is then applied to the GPR data from the Chang'E-4 mission at the Von Karman crater, revealing a previously unseen layered structure and a complex distribution of rocks/boulders

Human vision is determined based on information theory

Acknowledgements A.D.-B. wants to acknowledge to the Energy research program of Fundación Iberdrola España for the 2015 Fellowship award which partially funded this investigation.Peer reviewedPublisher PD

Abiotic Input of Fixed Nitrogen by Bolide Impacts to Gale Crater During the Hesperian: Insights From the Mars Science Laboratory

Molecular hydrogen (H2) from volcanic emissions is suggested to warm the Martian surface when carbon dioxide (CO2) levels dropped from the Noachian (4100 to 3700 Myr) to the Hesperian (3700 to 3000 Myr). Its presence is expected to shift the conversion of molecular nitrogen (N2) into different forms of fixed nitrogen (N). Here we present experimental data and theoretical calculations that investigate the efficiency of nitrogen fixation by bolide impacts in CO2‐N2 atmospheres with or without H2. Surprisingly, nitric oxide (NO) was produced more efficiently in 20% H2 in spite of being a reducing agent and not likely to increase the rate of nitrogen oxidation. Nevertheless, its presence led to a faster cooling of the shock wave raising the freeze‐out temperature of NO resulting in an enhanced yield. We estimate that the nitrogen fixation rate by bolide impacts varied from 7 × 10−4 to 2 × 10−3 g N·Myr−1·cm−2 and could imply fluvial concentration to explain the nitrogen (1.4 ± 0.7 g N·Myr−1·cm−2) detected as nitrite (NO2 −) and nitrate (NO3 −) by Curiosity at Yellowknife Bay. One possible explanation is that the nitrogen detected in the lacustrine sediments at Gale was deposited entirely on the crater's surface and was subsequently dissolved and transported by superficial and ground waters to the lake during favorable wet climatic conditions. The nitrogen content sharply decreases in younger sediments of the Murray formation suggesting a decline of H2 in the atmosphere and the rise of oxidizing conditions causing a shortage in the supply to putative microbial life.We acknowledge the NASA Mars Science Laboratory Program, Centre National d'Études Spatiales, the Universidad Nacional Autónoma de México (PAPIIT IN109416, IN111619, and PAPIME PE103216), and the Consejo Nacional de Ciencia y Tecnología de México (CONACyT 220626) for their support

High-resolution dynamical downscaling of re-analysis data over the Kerguelen Islands using the WRF model

We have used theWeather Research and Forecasting (WRF) model to simulate the climate of the Kerguelen Islands (49° S, 69° E) and investigate its inter-annual variability. Here, we have dynamically downscaled 30 years of the Climate Forecast System Reanalysis (CFSR) over these islands at 3-km horizontal resolution. The model output is found to agree well with the station and radiosonde data at the Port-aux-Français station, the only location in the islands for which observational data is available. An analysis of the seasonal mean WRF data showed a general increase in precipitation and decrease in temperature with elevation. The largest seasonal rainfall amounts occur at the highest elevations of the Cook Ice Cap in winter where the summer mean temperature is around 0 °C. Five modes of variability are considered: conventional and Modoki El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Subtropical IOD (SIOD) and Southern Annular Mode (SAM). It is concluded that a key mechanism by which these modes impact the local climate is through interaction with the diurnal cycle in particular in the summer season when it has a larger magnitude. One of the most affected regions is the area just to the east of the Cook Ice Cap extending into the lower elevations between the Gallieni and Courbet Peninsulas. The WRF simulation shows that despite the small annual variability, the atmospheric flow in the Kerguelen Islands is rather complex which may also be the case for the other islands located in the Southern Hemisphere at similar latitudes

Middle atmosphere OH NLTE model and spectroscopy sensitivity study

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Should We Invest in Martian Brine Research to Reduce Mars Exploration Costs?

Peer reviewedPublisher PD

Evaluación de la toxicidad de metilparabeno en Artemia franciscana: efectos sobre crecimiento, supervivencia y biomarcadores

En la actualidad se utiliza a diario gran cantidad de productos con parabenos en su composición. Debido a su uso masivo, cada vez se detectan mayores cantidades de parabenos en medios acuáticos. En este estudio se analiza la toxicidad de un contaminante emergente, como es el metilparabeno, en Artemia franciscana, dada la presencia de este compuesto en zonas costeras y salinas mediterráneas. Para ello, se realizó un diseño experimental para determinar la toxicidad aguda (LC50), así como el efecto crónico tras la exposición a dos concentraciones subletales (0.05 y 0.1 ppm) durante 9 días, sobre diferentes parámetros fisiológicos y bioquímicos, tales como la supervivencia, crecimiento, actividad de las enzimas colinesterasa y glutatión-S-transferasa y ratio de RNA/DNA. Los nauplios de A. franciscana son poco sensibles al MeP, (LC50-24 h de 131.4 ppm). El metilparabeno afecta significativamente a la supervivencia y crecimiento en exposiciones crónicas a las concentraciones subletales ensayadas (0.05 y 0.1 ppm). Además, éstas causan alteraciones significativas de la actividad colinesterasa, mientras que no se observa ningún efecto sobre la actividad glutatión-S-transferasa y la ratio RNA/DNA. Estos resultados indican que A. franciscana es resistente al metilparabeno, aunque exposiciones crónicas (hasta 9 días) a concentraciones subletales sí producen alteraciones en supervivencia y crecimiento. Además, la actividad colinesterasa es un biomarcador sensible a este compuesto mientras que la actividad glutatión-S-transferasa y la ratio RNA/DNA no presentan alteraciones.Peer Reviewe

The Impact of the Spectral Radiation Environment on the Maximum Absorption Wavelengths of Human Vision and Other Species

Funding: This research was funded by the Knut and Alice Wallenberg Foundation, The County Administrative Board of Norrbotten and Luleå University of Technology. M.-P.Z.’s research at CAB was partially supported by the Spanish State Research Agency (AEI), project no. MDM-2017-0737 Unidad de Excelencia ‘María de Maeztu’- Centro de Astrobiología (INTA-CSIC). Acknowledgments: The authors acknowledge support from the Wallenberg Foundation (KAW 2016.0346).Peer reviewedPublisher PD

Millimeter-wave aperture synthesis radiometry for snow and ice mapping

An outline design for a dual-band mm-wave polarimetric SAIR has been presented and is considered to be tractable. The envisaged application is for snow and ice mapping and ocean wind vector measurement. The vastly increased complexity of the high-frequency waveband may not be justified by the scientific benefit and operation at an additional lower frequency such as 18 GHz may give improved classification, though with reduced spatial resolution. The authors describe the outline design for a polarimetric, mm-wave SAIR. One-dimensional aperture synthesis employs a hybrid technique in which a long linear array of real-aperture stick antennas form over-lapping fan beams on the ground and aperture synthesis within the fan beams enables synthesis of the mm-wave image. Critical aspects for building a high-resolution, mm-wave ESTAR are system calibration and the construction of stick antennas that will be 3 m long and about half a wavelength wide.Peer ReviewedPostprint (published version

Experimental investigation of the atmosphere‐regolith water cycle on present‐day mars

Funding: The Kempe Foundation (SMK-1934) funded the design and fabrication of the SpaceQ chamber. M.-P.Z. has been partially funded by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu”- Centro de Astrobiología (INTA-CSIC) and by the Spanish Ministry of Science and Innovation (PID2019-104205GB-C21). A.V.R. and J.M.-T. acknowledge support from the Knut and Alice Wallenberg Foundation (KAW 2016.0346). Acknowledgments: We acknowledge the support from the Kurt J. Lesker Company on its construction. We thank Roberto Mantas Nakhai and Juan Antonio Ramírez Luque for their help in the data processing.Peer reviewedPublisher PD