Ondřej Šrámek

Charles University in Prague | CUNI · Department of Geophysics

Although the effect of ionising radiation on prebiotic chemistry is often overlooked, primordial natural radioactivity might have been an important source of energy for various chemical transformations. Estimates of the abundances of short-lived radionuclides on early Earth suggest that the primordial intensity of endogenous terrestrial radioactivi...

The Jiangmen Underground Neutrino Observatory~(JUNO) features a 20~kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent experiment for $^8$B solar neutrino measurements, such as its low-energy threshold, its high energy resolution compared to water Cherenkov detectors, and its mu...

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolut...

The role of heat flow coming from the core is often overlooked or underestimated in simple models of Earth's thermal evolution. Throughout most of Earth's history, the mantle must have been extracting from the core at least the amount of heat that is required to operate the geodynamo. In view of recent laboratory measurements and theoretical calcul...

Debate continues on the amount and distribution of radioactive heat producing elements (i.e., U, Th, and K) in the Earth, with estimates for mantle heat production varying by an order of magnitude. Constraints on the bulk‐silicate Earth's (BSE) radiogenic power also places constraints on overall BSE composition. Geoneutrino detection is a direct me...

Geoneutrinos are electron neutrinos and antineutrinos emitted in radioactive decays of radionuclides naturally occurring in the Earth. Thanks to experimental advances in fundamental neutrino research, geoneutrinos from ²³²Th and ²³⁸U decay chains have now been independently measured by two experiments, and more measurements are expected in the comi...

We report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short-lived radionuclides (SLR) and long-lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of the beta spectra. We carefully account for all branches in K...

Debate continues on the amount and distribution of radioactive heat producing elements (i.e., U, Th, and K) in the Earth, with estimates for mantle heat production varying by an order of magnitude. Constraints on the bulk-silicate Earth's (BSE) radiogenic power also places constraints on overall BSE composition. Geoneutrino detection is a direct me...

In response to the growing need for low-radioactivity argon, community experts and interested parties came together for a 2-day workshop to discuss the worldwide low-radioactivity argon needs and the challenges associated with its production and characterization. Several topics were covered: experimental needs and requirements for low-radioactivity...

Models that envisage successful subduction channel transport of upper crustal materials below 300 km depth, past a critical phase transition in buoyant crustal lithologies, are capable of accumulating and assembling these materials into so-called "second continents" that are gravitationally stabilized at the base of the Transition Zone, at some 600...

Radioactive decay of potassium (K), thorium (Th), and uranium (U) power the Earth's engine, with variations in 232Th/238U recording planetary differentiation, atmospheric oxidation, and biologically mediated processes. We report several thousand $^{232}$Th/$^{238}$U ($\kappa$) and time-integrated Pb isotopic ($\kappa$$_{Pb}$) values and assess thei...

The China Jinping Underground Laboratory (CJPL), which has the lowest cosmic-ray muon flux and the lowest reactor neutrino flux of any laboratory, is ideal to carry out low-energy neutrino experiments. With two detectors and a total fiducial mass of 2000 tons for solar neutrino physics (equivalently, 3000 tons for geo-neutrino and supernova neutrin...

The Earth's engine is driven by unknown proportions of primordial energy and heat produced in radioactive decay. Unfortunately, competing models of Earth's composition reveal an order of magnitude uncertainty in the amount of radiogenic power driving mantle dynamics. Recent measurements of the Earth's flux of geoneutrinos, electron antineutrinos fr...

Accurate understanding of the subsurface production of radionuclide $^{39}$Ar rate is necessary for argon dating techniques and noble gas geochemistry of the shallow and the deep Earth, and is also of interest to the WIMP dark matter experimental particle physics community. Our new calculations of subsurface production of neutrons, $^{21}$Ne, and $...

We present the current status of geo-neutrino measurements and their implications for radiogenic heating in the mantle. Earth models predict different levels of radiogenic heating and, therefore, different geo-neutrino fluxes from the mantle. Seismic tomography reveals features in the deep mantle possibly correlated with radiogenic heating and caus...

This issue’s “News in Brief” article takes a look at recent emerging research in neutrino geoscience. Geochemist William F. McDonough and geophysicist Ondřej Šrámek from the Department of Geology at the University of Maryland provide considerable insight into the research work and advancements on Earth’s heat budget and interior using geoneutrino m...

Knowledge of the amount and distribution of radiogenic heating in the mantle is crucial for understanding the dynamics of the Earth, including its thermal evolution, the style and planform of mantle convection, and the energetics of the core. Although the flux of heat from the surface of the planet is robustly estimated, the contributions of radiog...

Neutrino geophysics is an emerging interdisciplinary field with the potential to map the abundances and distribution of radiogenic heat sources in the continental crust and deep Earth. To date, data from two different experiments quantify the amount of Th and U in the Earth and begin to put constraints on radiogenic power in the Earth available for...

In early Solar System during the runaway growth stage of planetary formation, the distribution of planetary bodies progressively evolved from a large number of planetesimals to a smaller number of objects with a few dominant embryos. Here, we study the possible thermal and compositional evolution of these planetesimals and planetary embryos in a se...

A recently proposed model links the formation and early evolution of the Tharsis volcanic province on Mars to the preexisting hemispheric dichotomy (Zhong, 2009). A key aspect of this model is the assumption of a deep lithospheric root below the thicker crust of the southern highlands. We implemented a parameterization of partial melting into the 3...

Knowledge of the abundances and spatial distribution of heat producing elements in the Earth's interior is crucial for understanding the heat budget of the Earth, its thermal evolution, the style and planform of mantle convection and the overall architecture of the mantle. However, mantle composition and heat budget remain poorly constrained. The p...

Recent dating of iron meteorites shows that they were formed almost as early as the oldest known objects of the solar system, the CAIs. Moreover, several meteorites show a magnetization that is thought to originate from the action of a dynamo at the early stages of the planetesimals evolution. Core formation requires melting of the metal which then...

Core formation, crystal/melt separation, mingling of immiscible magmas, and diapirism are fundamental geological processes that involve differential motions driven by gravity. Diffusion modifies the composition or/and temperature of the considered phases while they travel. Solid particles, liquid drops and viscous diapirs equilibrate while sinking/...

The Tharsis bulge is the largest magmatic/volcanic center on Mars and in the solar system, having a volume of ~3×108km3, with the majority of its mass emplaced more than 3.7billion years ago. The igneous history of Tharsis has been implicated in the generation of an atmosphere and hydrosphere capable of clement conditions on early Mars. It has been...

We investigate the effect of partial melt residue stiffening on the plume-lithosphere dynamics on Mars, in order to further test a self-consistent endogenic model of dichotomy formation by partial melting and the subsequent Tharsis evolution.

The hemispheric crustal dichotomy and the Tharsis volcanic province are major global physiographic features on Mars, whose origin has not yet been satisfactorily explained. Hypotheses for the dichotomy origin invoke both external causes (i.e., a giant impact) and mechanisms of internal dynamics (e.g., long-wavelength mantle convection, or a large-s...

A dynamic link between the early evolution of Tharsis and the crustal dichotomy on Mars was recently proposed by Zhong (2009). We address in detail the fundamental aspects of the proposed model using 3-D spherical shell modeling of convection. We investigate the conditions under which a spherical harmonic degree 1 flow is produced in the mantle of...

In early Solar System during the runaway growth stage of planetary planetary formation, the distribution of planetary bodies progressively evolved from a large number of planetesimals to a smaller number of objects with a few dominant planetary embryos. Over a few millions years after the condensation of the first solids in the solar nebula, the gr...

The differentiation of solid planets with segregation of metal from silicates happens during the Hadean time while the planet is still growing by accretion. The separation of metal occurs when at least the metallic phase is liquid and proceeds by a combination of transport by diapiric instabilities and by more diffuse percolation flow. In this pape...

We present a series of models to test the ``rotation of the lithosphere'' hypothesis of Zhong (2009 Nature Geosci.) that links the evolution of Tharsis to the hemispheric dichotomy on Mars.

The hemispheric dichotomy and Tharsis volcanic province are dominant planetary scale features on Mars. The formation mechanism of the dichotomy remains unclear and arguments have been made for both exogenic (i.e., giant impact) and endogenic (i.e., related to internal dynamics) origin. A recently proposed model by Zhong (2009) aims to link the form...

The differentiation of terrestrial planets with segregation of metal from silicates took place contemporaneously with the last stage of planetary accretion and was likely completed in few tens of Myrs. The separation of metal occurs when at least the metallic phase is liquid and proceeds via a combination of transport by diapiric instabilities, a m...

A classic scenario of core formation suggests that growing proto-planets are heated by the impacts of accreting planetesimals at their surface until their shallow layers reach the melting temperature of their metallic components or even of the silicates. In this partially molten shell, metal and silicates differentiate and the metallic phase ponds...

We compute dynamic stresses at martian surface in the model of rotation of the lithosphere and we will discuss the implications for the martian tectonics.

Endogenic and exogenic formation mechanisms for the crustal dichotomy and their consequences on mantle dynamics, melting and volcanism are critically compared and examined.

La fusion partielle et le transport des magmas jouent un rôle majeur dans la formation et l’évolution de la planète Terre. Le transport de la chaleur, la rhéologie de roches et la distribution des éléments chimiques majeurs et mineurs, ainsi que de volatils sont tous affectés par la présence et la migration de magmas. La fusion partielle et l’extra...

Melt generation and extraction are typically modelled using the two-phase equations developed by McKenzie or Scott and Stevenson. Various approximations are often made to simplify the problem which may lead to some unphysical results (e.g. thermodynamically inconsistent conditions of melting and unrealistic porosity profiles). We discuss a generali...

Melting and deformation that accompanies segregation and extraction of melts are usually decoupled in geodynamical models, so that the effect of material flow on the thermodynamic conditions of melting is neglected. Moreover, often the extent and spacial distribution of melting are a priori prescribed, or melting is considered instantaneous, such t...

Melt generation and extraction are often modeled using the two-phase equations developed by McKenzie (1984). Usually the generation of melt and its subsequent propagation are treated independently which may lead to some unphysical results. Here, we discuss a generalized version of the set of equations introduced by Bercovici et al. (2001) that allo...

The observed long-wavelength non-hydrostatic geoid is usually interpreted as a re- sult of long-term convection processes in the Earth’s mantle. Contributions of other dynamic processes, such as postglacial rebound, are usually neglected. We attempt to quantify the error of such approach. On the basis of ICE-3G deglaciation model we solve the forwa...