Nature Astronomy / 3, 916–921 (2019)
Abstract: The surface of the dwarf planet Ceres is considered to be dominated by geological processes typical of small bodies or medium-sized icy bodies, such as impact cratering; there are also features of putative cryovolcanic origin as well as those related to flow of near-surface ice. Extensional features include regional linear troughs, fractures and pit chains, fractures associated with impact craters and with crater floors, and polygonal craters whose walls seem to be structurally controlled. However, no contractional features, which are related to thrust fault activity more typical of large silicate bodies, have been described. Here we report the presence of scarps, ridges and fractures associated with thrust faults, tectonically raised terrains and thrusted craters—all contractional features. These structures closely resemble thrust-fault-related lobate scarps on Mercury and Mars, albeit with lower displacement. They seem more abundant in high-latitude ancient terrains, perhaps owing to illumination effects that aid identification. The observed deformation implies that the crustal material is stronger than water ice but weaker than silicate rocks, consistent with our current knowledge of crustal composition and rheology. These features suggest that large-scale contraction, possibly related to differentiation processes, occurred in the history of Ceres.
Abstract: Elysium Planitia and Oxia Planum are plains located near the Martian dichotomy. Lately, both regions have been extensively analyzed due to the major role that they play in the InSight and ExoMars missions. InSight landed in Elysium Planitia and will obtain the first direct measurement of surface heat flow on Mars. Similarly, the Rosalind Franklin rover on ExoMars 2020 will also provide useful information to understand the thermal state of the planet from data acquired in Oxia Planum, which is the preferred landing site. The proximity of the Martian dichotomy to the area surrounding both landing locations is an important source of spatial variability. In this work, we have modeled the heat flow and the subsurface temperature in the regions adjacent to both landing sites considering the regional context. In order to do so, we have solved the heat conduction equation by means of a finite element analysis and by taking into account topography, crustal composition, and crustal and megaregolith thicknesses. Our results indicate that the spatial variation in these parameters for the region surrounding the InSight landing site involves maximum differences in subsurface temperatures and surface heat flows between highlands and lowlands of about 67% and 16%, respectively. In regard to the area surrounding ExoMars landing site, these differences can reach 28% for subsurface temperatures, and 3% for surface heat flows. Crustal and megaregolith thicknesses together with the thermal properties of the megaregolith layer are the most influential factors affecting heat flows and temperature patterns. We also find that regional variations related to the dichotomy boundary are unlikely to have a large effect on the geothermal heat flux at the InSight and ExoMars landing sites.
Ruiz, J., Jiménez-Díaz, A., Egea-González, I., Parro, L. M., Mansilla, F.
Icarus / 322, 221-226 (2019)
Abstract: Two recent papers, by Karimi et al. (2016, Icarus 272, 102–113) and Karimi and Dombard (2017, Icarus 282, 34–39), tried to deduce paleo-heat flows for, respectively, Mars and Venus from modeling the viscoelastic relaxation of large impact craters. Indeed, crater relaxation would be consequence of the flow of the lower crust and uppermost mantle. This flow is dependent on temperature, permitting the link with the calculation of thermal profiles and heat flows. Both papers used conductive thermal profiles and constant thermal conductivities for both the crust and upper mantle (equivalent to using linear thermal gradients given there were no mention to crustal or mantle heat sources), and appropriate rheological laws. In the present discussion, we show that the background heat flows contemporaneous to impact craters formation and relaxation obtained by Karimi and co-workers, when used along with the assumptions made by these authors, lead to temperatures that produce massive (even total) lower crust melting in all and at least a substantial part of the cases for, respectively, Venus and Mars. It is clear that the heat flow results presented by Karimi and co-workers suffer of inconsistency between model requirements explicitly indicated (a crust free of melting) and the implications of the obtained basal heat flows (a lowermost crust partially or totally molten). Thus, we consider that the papers by Karimi and co-workers do not give reliable information on the thermal history of Mars and Venus.
Scientific Reports / 7, 45629 (2017)
Abstract: Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m−2, with an average value of 19 mW m−2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7–0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic.
Icarus / 288, 53-68 (2017)
Abstract: The circum-Hellas area of Mars borders Hellas Planitia, a giant impact ∼4.0–4.2 Ga old making the deepest and broadest depression on Mars, and is characterized by a complex pattern of fracture sets, lobate scarps, grabens, and volcanic plains. The numerous lobate scarps in the circum-Hellas region mainly formed in the Late Noachian and, except Amenthes Rupes, have been scarcely studied. In this work, we study the mechanical behavior and thermal structure of the crust in the circum-Hellas region at the time of lobate scarp formation, through the modeling of the depth of faulting beneath several prominent lobate scarps. We obtain faulting depths between ∼13 and 38 km, depending on the lobate scarp and accounting for uncertainty. These results indicate low surface and mantle heat flows in Noachian to Early Hesperian times, in agreement with heat flow estimates derived from lithospheric strength for several regions of similar age on Mars. Also, faulting depth and associate heat flows are not dependent of the local crustal thickness, which supports a stratified crust in the circum-Hellas region, with heat-producing elements concentrated in an upper layer that is thinner than the whole crust.
Planetary and Space Science / 130, 24-29 (2016)
Abstract: Chaos terrains are among the most prominent landforms of Europa, and are generally among the youngest features recorded on the surface. Chaos units were formed by to endogenic activity, maybe related to solid-state convection and thermal diapirism in the ice shell, perhaps aided by melting of salt-rich ice bodies below the surface. In this work, we analyze the different units of chaotic terrain in a portion of Argadnel Regio, a region located on the anti-Jovian hemisphere of Europa, and their possible timing in the general stratigraphic framework of this satellite. Two different chaos units can be differentiated, based on surface texture, morphology, and cross-cutting relationships with other units, and from interpretations based on pre-existing surface restoration through elimination of a low albedo band. The existence of two stratigraphically different chaos units implies that conditions for chaos formation occurred during more than a single discreet time on Europa, at least in Argadnel Regio, and perhaps in other places. The existence of older chaos units on Europa might be related to convective episodes possibly favored by local conditions in the icy shell, such as variations in grain size, abundance of non-water ice-components, or regional thickness of the brittle lithosphere or the entire ice shell.
Selected Conference Abstracts/Presentations
(2019) Ruiz, J., Jiménez-Díaz, A., Mansilla, F., Parro, L. M., Egea-González, I., Küppers, M. Thrust faulting and contraction of Ceres. VI CPESS. Madrid, Spain.
(2018) Parro, L.M., Mansilla, F., Herrero-Gil, A. Viajando por Planetas en la Semana de la Ciencia: Un proyecto de divulgación de las Ciencias Planetarias. XIII SEA. Salamanca, Spain.
(2018) Egea-Gonzalez, I., Parro, L.M., Jiménez-Díaz, A., Mansilla, F., Herrero-Gil, I., Ruiz., J. Local heat flow and subsurface temperature in InSight landing-site. XIII SEA. Salamanca, Spain.
(2018) Parro, L.M., Jiménez-Díaz, A., Egea-Gonzalez, I., Mansilla, F., Ruiz., J. Marte: Evolución térmica y estructura de su corteza. XIII SEA. Salamanca, Spain.
(2018) Parro, L.M., A. Jiménez-Díaz, F. Mansilla, I. Egea-González, J. Ruiz. Heat flow and thermal structure of the Martian lithosphere. Scientific Workshop: “From Mars Express to ExoMars”, Madrid, Spain.
(2017) Jiménez-Díaz, A., Egea-González, I., Parro, L.M., Tasaka, M., Ruiz, J. On the structure of the lithosphere of Mars: New insights from crustal composition and rheology of the upper mantle. EPSC 2016, Riga, Latvia.
(2017) Galvez, F. Ballesteros, A. García-Frank, S. Gil, A. Gil-Ortiz, M. Gómez-Heras, J. Martínez-Frías, L. M. Parro, V. Parro, E. Pérez-Montero, V. Raposo, and J. A. Vaquerizo. Inclusive Planetary Science Outreach and Education: a Pioneering European Experience. EPSC 2016, Riga, Latvia.
(2017) Parro, L.M., Jiménez-Díaz, A., Ruiz, J. El estudio integrado de la litosfera de Marte. V CPESS. Madrid, Spain.
(2017) Jiménez-Díaz, A., Egea-González, I., Parro, L.M., Ruiz, J. La corteza de Marte y su influencia sobre las propiedades térmicas y mecánicas de la litosfera. V CPESS. Madrid, Spain.
(2017) Ruiz, J., Egea-González, I., Fernández, C., Herrero-Gil, A., Jiménez-Diaz, A., López, V., Mansilla, F., Parro, L., Romeo, I., Williams, J.-P. “Follow the scarps”: claves sobre la evolución y propiedades de los cuerpos planetarios aportadas por escarpes asociados a grandes fallas inversas. V CPESS. Madrid, Spain.
(2017) Jiménez-Díaz, A., Egea-González, I., Parro, L.M., Ruiz, J. On the thermo-mechanical structure of the Martian lithosphere: the role of the crust. 48th LPSC, The Woodlands, TX, USA.
(2016) Parro, L.M., Jiménez-Díaz, A., Mansilla, F., Ruiz, J. The present-day heat flow structure of Mars. AGU Fall Meeting 2016, San Francisco, CA, USA.
(2015) Parro, L.M., Jiménez-Díaz, A., Ruiz, J. Current thermal state of Mars from scaled models of surface heat flow. EPSC 2015, Nantes, France.
(2015) Parro, L. M., Jiménez-Díaz, A., Ruiz, J. Investigación del estado térmico actual de Marte, a partir de modelos de producción de calor y flujo térmico. IV CPESS. Alicante, Spain.
(2015) M. A. López-Valverde, F. González-Galindo, B. Funke, M. García-Comas, M. López-Puertas, J. J. López-Moreno, S. Jimenez-Monferrer, J. Ruiz, L. M. Parro, A. Jimenez-Diaz and the UPWARDS team. UPWARDS: An integral study of Mars in preparation for Exomars. IV CPESS. Alicante, Spain.
(2014) Parro, L. M., Pappalardo, R. T., Ruiz, J. Chaos units in Argadnel Regio, Europa, and implications for geological history. EPSC 2014, Cascais, Portugal.
(2014) Álvarez-Gómez, J. A., Parro, L. M., Aniel-Quiroga, I., González, M., Al-Yahyai, S., Martínez, J., Méndez, F., Rueda, A., Medina, R. Tsunamigenic seismic sources characterization in the Zagros fold and thrust belt. Implications for tsunami threat in the Persian Gulf. EGU 2014, Vienna, Austria.
(2014) Parro, L. M., Ruiz, J., Pappalardo, R. T. Chaos units in Argadnel Regio, Europa: implications for timing of chaos formation. 45th LPSC, The Woodlands, TX, USA.
(2013) Parro, L. M., Ruiz, J., Pappalardo, R. T. Terrenos caóticos e historia geológica en Argadnel Regio, Europa. III CPESS. Madrid, Spain.
(2013) Pimentel, C., Alloza, L. J., Caravantes, G., Jiménez-Díaz, A., López, V., Martín-Herrero, Á., Parro, L. M., Romeo, I., Ruiz, J. Grupo de Ciencias Planetarias de Madrid (GCPM). III CPESS. Madrid, Spain.
(2013) Ruiz, J., McGovern, P. J., Parro, L. M., López, V. Paleo-heat flow and the magnetic and climatic history of Mars. 44th LPSC, The Woodlands, TX, USA.