Persona: Martínez, Germán M.
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Centro de Astrobiologia
El Centro de Astrobiología (CAB) es un centro mixto de investigación en astrobiología, dependiente tanto del Instituto Nacional de Técnica Aeroespacial (INTA) como del Consejo Superior de Investigaciones Científicas (CSIC).
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Martínez
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Germán M.
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Publicación Acceso Abierto In Situ UV Measurements by MSL/REMS: Dust Deposition and Angular Response Corrections(Springer Link, 2020-07-21) Vicente Retortillo, Álvaro; Martínez, Germán M.; Rennó, N. O.; Lemmon, M. T.; De la Torre Juárez, M.; Gómez Elvira, J.; NASA Jet Propulsion Laboratory (JPL); Retortillo, A. V. [0000-0002-4553-7624]; Gómez Elvira, J. [0000-0002-9068-9846]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737Measurements by the REMS/UV sensor onboard the MSL Curiosity rover constitute the first in situ dataset of UV radiation flux at the surface of Mars. Due to its position on the Curiosity deck, the UV sensor has been directly exposed to dust deposition. Inaccuracies in the original angular response calibration functions have led to discrepancies between measured and physically-expected UV fluxes when the solar zenith angle (theta) relative to the rover frame is between 20 degrees and 55 degrees. Here we present a methodology to correct UV fluxes when theta < 55 degrees for both effects, and show results of the corrected data set for the first 2003 sols (similar to 3 Martian Years, MY) of the MSL mission, from L-s similar to 151 degrees in MY 31 to L-s similar to 149 degrees in MY 34. Close to noon, when. values are typically < 30 degrees, relative differences between corrected and original UV fluxes are similar to 35 - 40% on average. Outside hours close to noon, when theta is typically > 30 degrees, relative differences are greater than 100%. Measurements acquired when 20 degrees < theta < 55 degrees represent similar to 45% of the whole dataset with theta < 90 degrees. UV fluxes generated in this study are available in the NASA Planetary Data System (https://atmos.nmsu.edu/PDS/data/mslrem_1001/DATA_UV_CORRECTED/), and are important to study the effect of UV radiation on the variability of atmospheric constituents, to recreate accurate UV doses for biological laboratory experiments, to perform combined analyses of satellite and ground-based measurements, and to allow comparisons of the UV radiation environment at different locations with the upcoming ExoMars 2020 and Mars 2020 missions.Publicación Acceso Abierto The Mars Environmental Dynamics Analyzer, MEDA. A Suite of Environmental Sensors for the Mars 2020 Mission(Springer Link, 2021-04-13) Rodríguez Manfredi, J. A.; De la Torre Juárez, M.; Alonso, A.; Apéstigue, Víctor; Arruego, Ignacio; Atienza, T.; Banfield, D.; Boland, J.; Carrera, M. A.; Castañer, L.; Ceballos Cáceres, J.; Chen Chen, H.; Cobos, A.; Conrad, Pamela G.; Cordoba, E.; Del Río Gaztelurrutia, T.; Vicente Retortillo, Álvaro; Domínguez Pumar, M.; Espejo, S.; Fairén, Alberto G.; Fernández Palma, A.; Ferrándiz, Ricardo; Ferri, F.; Fischer, E.; García Manchado, A.; García Villadangos, M.; Genzer, María; Giménez, Á.; Gómez Elvira, J.; Gómez, Felipe; Guzewich, Scott; Harri, Ari-Matti; Hernández, C. D.; Hieta, M.; Hueso, R.; Jaakonaho, I.; Jiménez Martín, Juan José; Jiménez, V.; Larman, A.; Leiter, R.; Lepinette Malvitte, A.; Lemmon, M. T.; López, G.; Madsen, Soren N.; Mäkinen, T.; Marín Jiménez, M.; Martín Soler, J.; Martínez, Germán M.; Molina, A.; Mora Sotomayor, L.; Moreno Álvarez, J. F.; Navarro López, Sara; Newman, C. E.; Ortega, Cristina; Parrondo, María Concepción; Peinado, V.; Peña, A.; Pérez Grande, I. ; Pérez Hoyos, S.; Pla García, J.; Polkko, J.; Postigo, M.; Prieto-Ballesteros, Olga; Rafkin, Scot C. R.; Ramos, Miguel; Richardson, M. I.; Romeral, J.; Romero Guzmán, Catalina; Runyon, Kirby; Saiz López, A.; Sánchez Lavega, Agustín; Sard, I.; Schofield, J. T.; Sebastián, E.; Smith, Michael D.; Sullivan, Robert; Tamppari, L. K.; Thompson, A. D.; Toledo, D.; Torrero, F.; Torres, J.; Urquí, R.; Velasco, T.; Viúdez Moreiras, Daniel; Zurita, S.; Agencia Estatal de Investigación (AEI); European Research Council (ERC); Gobierno Vasco; Rodríguez Manfredi, J. A. [0000-0003-0461-9815]; Saiz López, A. [0000-0002-0060-1581]; Chen, H. [0000-0001-9662-0308]; Pérez Hoyos, S. [0000-0002-2587-4682]NASA’s Mars 2020 (M2020) rover mission includes a suite of sensors to monitor current environmental conditions near the surface of Mars and to constrain bulk aerosol properties from changes in atmospheric radiation at the surface. The Mars Environmental Dynamics Analyzer (MEDA) consists of a set of meteorological sensors including wind sensor, a barometer, a relative humidity sensor, a set of 5 thermocouples to measure atmospheric temperature at ∼1.5 m and ∼0.5 m above the surface, a set of thermopiles to characterize the thermal IR brightness temperatures of the surface and the lower atmosphere. MEDA adds a radiation and dust sensor to monitor the optical atmospheric properties that can be used to infer bulk aerosol physical properties such as particle size distribution, non-sphericity, and concentration. The MEDA package and its scientific purpose are described in this document as well as how it responded to the calibration tests and how it helps prepare for the human exploration of Mars. A comparison is also presented to previous environmental monitoring payloads landed on Mars on the Viking, Pathfinder, Phoenix, MSL, and InSight spacecraft.Publicación Acceso Abierto Convective Vortices and Dust Devils Detected and Characterized by Mars 2020(AGU Advancing Earth and Space Science, 2023-02-10) Hueso, R.; Newman, C. E.; Del Río Gaztelurrutia, T.; Munguira, A.; Sánchez Lavega, Agustín; Toledo, D. ; Apéstigue, Víctor; Arruego, Ignacio; Vicente Retortillo, Álvaro; Martínez, Germán M.; Lemmon, M. T.; Lorenz, Ralph; Richardson, M. I.; Viúdez Moreiras, Daniel; De la Torre Juárez, M.; Rodríguez Manfredi, J. A.; Tamppari, L. K.; Murdoch, N.; Navarro López, Sara; Gómez Elvira, J.; Baker, M.; Pla García, J.; Harri, Ari-Matti; Hieta, M.; Genzer, María; Polkko, J.; Jaakonaho, I.; Makinen, Terhi; Stott, Alexander; Mimoun, D.; Chide, B.; Sebastián Martínez, Eduardo; Banfield, D.; Lepinette Malvitte, A.; Gobierno Vasco; Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Los Alamos National Laboratory (LANL); Arizona State University (ASU); Universities Space Research Association (USRA); NASA Jet Propulsion Laboratory (JPL); Comunidad de Madrid; Academy of Finland (AKA); Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737We characterize vortex and dust devils (DDs) at Jezero from pressure and winds obtained with the Mars Environmental Dynamics Analyzer (MEDA) instrument on Mars 2020 over 415 Martian days (sols) (Ls = 6°–213°). Vortices are abundant (4.9 per sol with pressure drops >0.5 Pa correcting from gaps in coverage) and they peak at noon. At least one in every five vortices carries dust, and 75% of all vortices with Δp > 2.0 Pa are dusty. Seasonal variability was small but DDs were abundant during a dust storm (Ls = 152°–156°). Vortices are more frequent and intense over terrains with lower thermal inertia favoring high daytime surface-to-air temperature gradients. We fit measurements of winds and pressure during DD encounters to models of vortices. We obtain vortex diameters that range from 5 to 135 m with a mean of 20 m, and from the frequency of close encounters we estimate a DD activity of 2.0–3.0 DDs km−2 sol−1. A comparison of MEDA observations with a Large Eddy Simulation of Jezero at Ls = 45° produces a similar result. Three 100-m size DDs passed within 30 m of the rover from what we estimate that the activity of DDs with diameters >100 m is 0.1 DDs km−2sol−1, implying that dust lifting is dominated by the largest vortices in Jezero. At least one vortex had a central pressure drop of 9.0 Pa and internal winds of 25 ms−1. The MEDA wind sensors were partially damaged during two DD encounters whose characteristics we elaborate in detail.Publicación Restringido Radiometric and angular calibration tests for the MEDA-TIRS radiometer onboard NASA’s Mars 2020 mission(Elsevier BV, 2020-11-02) Sebastián, E.; Martínez, Germán M.; Ramos, Miguel; Haenschke, F.; Ferrándiz, Ricardo; Fernández Sampedro, M.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Fernández Sampedro, M. [0000-0003-1932-7591]; Rodríguez Manfredi, J. A. [0000-0003-0461-9815]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737This article describes a comprehensive testing method for the radiometric and angular calibration of the Thermal InfraRed Sensor (TIRS) onboard NASA’s Mars 2020 mission. First, details of the TIRS opto-mechanical design, construction aspects of the IR detectors, and an update of the mathematical model used for the calculation of sensor internal IR fluxes are provided. Then, a set of sequential calibration tests to identify the radiometer model parameters are defined. The test setups are described, highlighting their limitations and restrictions based on differences between simulated and actual Martian environmental conditions. Finally, the uncertainty sources and potential systematic errors associated with the calibration tests are quantified and compared with the radiometer scientific requirements established by the Mars 2020 science team.Publicación Restringido Model Update and Surface Operation Performance of the MEDA-TIRS Radiometer Onboard NASA’s Mars 2020 Perseverance Rover(Springer Nature, 2025-07-14) Sebastián Martínez, Eduardo; Martínez, Germán M.; Smith, Michael; Peinado, V.; Mora Sotomayor, L.; Vicente Retortillo, Álvaro; Rodríguez Manfredi, J. A.; Ministerio de Economía y Competitividad (MINECO); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); National Aeronautics and Space Administration (NASA); Instituto Nacional de Técnica Aeroespacial (España); Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737We describe new updates in the data retrieval process of the Mars Environmental Dynamics Analyzer Thermal-InfraRed Sensor (MEDA-TIRS) onboard NASA’s Mars 2020 Perseverance rover and analyze its performance under these new updates for the first 700 sols of this mission. The primary goal of these updates is to reduce the uncertainty in each of the quantities measured by TIRS, thereby improving its performance in measuring atmospheric and ground temperature, reflected shortwave solar radiation, and the upwelling and downwelling longwave irradiances across the entire spectrum. Our updates include results from new modeling efforts and tests conducted during the cruise and operational phase on Mars to characterize the electronic conditioning system and to calculate new noise and offset values. Based on the annual degradation rates of the TIRS channel detectors due to dust deposition, we compare projected values of resolution and accuracy to pre-flight requirements. These projections are useful for estimating the radiometer’s lifetime and for using its data in the context of the future Mars Sample Return and other future mission.Publicación Acceso Abierto Lander and rover histories of dust accumulation on and removal from solar arrays on Mars(Elsevier, 2021-11-01) Lorenz, R. D.; Martínez, Germán M.; Spiga, A.; Vicente Retortillo, Álvaro; Newman, C. E.; Murdoch, N.; Forget, F.; Millour, E.; Pierron, T.; National Aeronautics and Space Administration (NASA); Agence Nationale de la Recherche (ANR); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737The degradation in electrical output of solar arrays on Mars landers and rovers is reviewed. A loss of 0.2% per Sol is typical, although observed rates of decrease in ‘dust factor’ vary between 0.05% and 2% per Sol. 0.2%/Sol has been observed throughout the first 800 Sols of the ongoing InSight mission, as well as the shorter Mars Pathfinder and Phoenix missions. This rate was also evident for much of the Spirit and Opportunity missions, but the degradation there was episodically reversed by cleaning events due to dust devils and gusts. The enduring success of those rover missions may have given an impression of the long-term viability of solar power on the Martian surface that is not globally-applicable: the occurrence of cleaning events with an operationally-useful frequency seems contingent upon local meteorological circumstances. The conditions for significant cleaning events have apparently not been realized at the InSight landing site, where, notably, dust devils have not been detected in imaging. Optical obscuration by dust deposition and removal has also been observed by ultraviolet sensors on Curiosity, with a similar (but slightly higher) degradation rate. The observations are compared with global circulation model (GCM) results: these predict a geographically somewhat uniform dust deposition rate, while there is some indication that the locations where cleaning events were more frequent may be associated with weaker background winds and a deeper planetary boundary layer. The conventional Dust Devil Activity metric in GCMs does not effectively predict the different dust histories.Publicación Acceso Abierto Dust Devil Frequency of Occurrence and Radiative Effects at Jezero Crater, Mars, as Measured by MEDA Radiation and Dust Sensor (RDS)(GU Advancing Earth and Space Science, 2023-01-17) Toledo, D.; Apéstigue, Víctor; Arruego, Ignacio; Lemmon, M. T.; Gómez Martín, L.; Montoro, F.; Hueso, R.; Newman, C. E.; Smith, Michael D.; Viúdez Moreiras, Daniel; Martínez, Germán M.; Vicente Retortillo, Álvaro; Sánchez Lavega, Agustín; De la Torre Juárez, M.; Rodríguez Manfredi, J. A.; Carrasco, I.; Yela González, Margarita; Jiménez Martín, Juan José; García-Menéndez, Elisa; Navarro López, Sara; Gómez Elvira, J.; Harri, Ari-Matti; Polkko, J.; Hieta, M.; Genzer, María; Murdoch, N.; Sebastián, E.; Agencia Estatal de Investigación (AEI); Ministerio de Ciencia e Innovación (MICINN); Ministerio de Economía y Competitividad (MINECO); NASA Jet Propulsion Laboratory (JPL); National Aeronautics and Space Administration (NASA); Gobierno VascoThe Mars Environmental Dynamics Analyzer, onboard the Perseverance rover, is a meteorological station that is operating on Mars and includes, among other sensors, the radiometer Radiation and Dust Sensor (RDS). From RDS irradiance observations, a total of 374 dust devils (DDs) were detected for the first 365 sols of the mission (Ls = 6°–182°), which along with wind and pressure measurements, we estimated a DD frequency of formation at Jezero between 1.3 and 3.4 DD km−2 sol−1 (increasing as we move from spring into summer). This frequency is found to be smaller than that estimated at the Spirit or Pathfinder landing sites but much greater than that derived at InSight landing site. The maximum in DD frequency occurs between 12:00 and 13:00 local true solar time, which is when the convective heat flux and lower planetary boundary layer IR heating are both predicted to peak in Jezero crater. DD diameter, minimum height, and trajectory were studied showing (a) an average diameter of 29 m (or a median of 25 m) and a maximum and minimum diameter of 132 ± 63.4 and 5.6 ± 5.5 m; (b) an average minimum DD height of 231 m and a maximum minimum-height of 872 m; and (c) the DD migration direction is in agreement with wind measurements. For all the cases, DDs decreased the UV irradiance, while at visible or near-IR wavelengths both increases and decreases were observed. Contrary to the frequency of formation, these results indicate similar DD characteristics in average for the studied period.Publicación Acceso Abierto Drying of the Martian mesosphere during aphelion induced by lower temperatures(Springer Nature, 2024-11-20) Toledo, D.; Rannou, P.; Apéstigue, Víctor; Rodríguez Veloso, Raúl; Rodríguez Manfredi, J. A.; Arruego, Ignacio; Martínez, Germán M.; Tamppari, L. K.; Munguira, A.; Lorenz, Ralph; Stcherbinine, Aurélien; Montmessin, F.; Sánchez Lavega, Agustín; Patel, P.; Smith, Michael D.; Lemmon, M. T.; Vicente Retortillo, Álvaro; Newman, C. E.; Viúdez Moreiras, Daniel; Hueso, R.; Bertrand, T.; Pla García, J.; Yela González, Margarita; De la Torre Juárez, M.; Ministerio de Ciencia e Innovación (MICINN); Jet Propulsion Laboratory (JPL); National Aeronautics and Space Administration (NASA); Gobierno Vasco; Agencia Estatal de Investigación (AEI); Unidad de Excelencia Científica María de Maeztu Instituto de Astrofísica de Cantabria, MDM-2017-0765The formation of water ice clouds or hazes on Mars imposes substantial limitations on the vertical transport of water into the middle-upper atmosphere, impacting the planet’s hydrogen loss. Recent observations made by the Mars Environmental Dynamics Analyzer instrument onboard Mars 2020 Perseverance rover have shown a marked decline in water ice abundance within the mesosphere (above 35-40 km) when Mars is near its aphelion (near the northern summer solstice), notably occurring during solar longitudes (Ls) between Ls 70∘ and 80∘. Orbital observations around the same latitudes indicate that temperatures between ~ 30-40 km reach a minimum during the same period. Using cloud microphysics simulations, we demonstrate that this decrease in temperature effectively increases the amount of water cold-trapped at those altitudes, confining water ice condensation to lower altitudes. Similarly, the reinforcement of the cold trap induced by the lower temperatures results in significant reductions in the water vapor mixing ratio above 35–40 km, explaining the confinement of water vapor observed around aphelion from orbiters.Publicación Acceso Abierto In-flight calibration of the MEDA-TIRS instrument onboard NASA's Mars2020 mission(Elsevier, 2024-11-09) Sebastián, E.; Martínez, Germán M.; Ramos, Miguel; Smith, Michael D.; Peinado, V.; Mora Sotomayor, L.; Lemmon, M. T.; Vicente Retortillo, Álvaro; de Lucas Veguillas, Javier; Ferrándiz, Ricardo; Rodríguez Manfredi, J. A.This article describes a novel procedure and algorithm used for the in-flight calibration of the Thermal Infrared Sensor (TIRS) onboard the Mars 2020 mission. The purpose is to recalibrate the responsivity of TIRS’ IR detectors as they degrade following surface operations and exposure to harsh environmental conditions. Using data from in-flight calibration campaigns conducted through sol 800 of this mission, we report the time evolution of the responsivity for the different IR detectors, as well as the final performance achieved by the algorithm in the real operating environment. Moreover, we analyzed changes in responsivity as a function of TIRS geometric design and environmental factors, e.g., detector orientation, direct exposure to prevailing winds and solar radiation, electrostatic properties of the detector filter, and atmospheric dust concentration. We concluded that dust deposition on the detectors' filter during landing, and later during operation is the most likely cause of the degradation observed in the various channels, with gravitational sedimentation and the capacity of the filters to accumulate electrostatic charge being key factors. The relative and absolute degradation of the TIRS is similar to those reported by other Martian missions and instruments with similar orientations, and to date, it has shown no signs of cleaning after more than a year on the surface of Mars. Accounting for changes in responsivity during the mission is critical to maintaining the reliability of TIRS measurements, which will later be made available in NASA's Planetary Data System for the benefit of the scientific community.Publicación Restringido Background levels of methane in Mars’ atmosphere show strong seasonal variations(Science, 2018-06-08) Webster, Christopher R.; Mahaffy, Paul R.; Atreya, Sushil K.; Moores, John E.; Flesch, Gregory J.; Malespin, Charles A.; McKay, Christopher P.; Martínez, Germán M.; Smith, Christina L.; Martín Torres, Javier; Gómez Elvira, J.; Zorzano, María-Paz; Wong, Michael H.; Trainer, Melissa G.; Steele, Andrew; Archer, Doug; Sutter, Brad; Coll, Patrice J.; Freissinet, Caroline; Meslin, Pierre-Yves; Gough, Raina V.; House, Christopher H.; Pavlov, Alexander; Eigenbrode, Jennifer L.; Glavin, Daniel P.; Pearson, John C.; Keymeulen, Didier; Christensen, Lance E.; Schwenzer, Susanne P.; Navarro González, R.; Pla García, J.; Rafkin, Scot C. R.; Vicente Retortillo, Álvaro; Kahanpää, H.; Viúdez Moreiras, Daniel; Smith, Michael D.; Harri, Ari-Matti; Genzer, María; Hassler, Donald M.; Lemmon, M. T.; Crisp, Joy; Sander, Stanley P.; Zurek, Richard W.; Vasavada, Ashwin R.; National Aeronautics and Space Administration (NASA)Variable levels of methane in the martian atmosphere have eluded explanation partly because the measurements are not repeatable in time or location. We report in situ measurements at Gale crater made over a 5-year period by the Tunable Laser Spectrometer on the Curiosity rover. The background levels of methane have a mean value 0.41 ± 0.16 parts per billion by volume (ppbv) (95% confidence interval) and exhibit a strong, repeatable seasonal variation (0.24 to 0.65 ppbv). This variation is greater than that predicted from either ultraviolet degradation of impact-delivered organics on the surface or from the annual surface pressure cycle. The large seasonal variation in the background and occurrences of higher temporary spikes (~7 ppbv) are consistent with small localized sources of methane released from martian surface or subsurface reservoirs.
