International Journal of Geophysics
Volume 2016 (2016), Article ID 4703168, 13 pages
http://dx.doi.org/10.1155/2016/4703168

Review Article

Planetary Sciences, Geodynamics, Impacts, Mass Extinctions, and Evolution: Developments and Interconnections

Jaime Urrutia-Fucugauchi and Ligia Pérez-Cruz

Programa Universitario de Perforaciones en Océanos y Continentes, Departamento de Geomagnetismo y Exploración Geofísica, Instituto de Geofísica, Universidad Nacional Autónoma de México, Delegación Coyoacán, 04510 Mexico City, DF, Mexico

Received 29 September 2015; Accepted 23 March 2016

Academic Editor: Robert Tenzer

Copyright © 2016 Jaime Urrutia-Fucugauchi and Ligia Pérez-Cruz. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Research frontiers in geophysics are being expanded, with development of new fields resulting from technological advances such as the Earth observation satellite network, global positioning system, high pressure-temperature physics, tomographic methods, and big data computing. Planetary missions and enhanced exoplanets detection capabilities, with discovery of a wide range of exoplanets and multiple systems, have renewed attention to models of planetary system formation and planet’s characteristics, Earth’s interior, and geodynamics, highlighting the need to better understand the Earth system, processes, and spatio-temporal scales. Here we review the emerging interconnections resulting from advances in planetary sciences, geodynamics, high pressure-temperature physics, meteorite impacts, and mass extinctions.

1. Introduction

In the 16th and 17th centuries, physics encompassed a wide field of inquiry with significant advances coming from many widely separated endeavors in what are now astronomy, optics, mechanics, gas chemistry, thermodynamics, and so forth. They included development of the heliocentric model for the solar system, formulation of the laws of planetary motion, experimental and mathematical descriptions of pendular and parabolic motion, the law of universal gravitation, inertial reference frame and laws of motion, the pressure-volume Boyle law, and the ideal gas law, among many other discoveries. Modern research in physics continues to encompass a wide field of inquiry, which is reflected into the different disciplines and emerging frontiers.

Increased awareness on the role of interactions among the Earth’s components of the atmosphere, hydrosphere, lithosphere, ionosphere, and biosphere (Figure 1) leads to integrative approaches in Earth system science. This has led to better understanding of interactions, component flow, and feedback mechanisms acting with distinct spatial-temporal scales and manifested in the geochemical cycles, surface processes, and Earth’s climate. Recent advances in the study of the Earth’s interior and external processes in the near Earth environment and the solar system are resulting in broad integrative approaches.

Figure 1: Earth system components connecting the Earth’s deep interior, core, mantle, lithosphere, atmosphere, oceans, magnetosphere, and ionosphere with external processes like asteroid impacts, cosmic radiation, and solar winds (credits: International Scientific Continental Drilling Program (ICDP) website: http://www.icdp-online.org).

Recent and long standing questions are being investigated using technological and theoretical developments, which include high performance computing, big data analysis, satellite observation system, instrumental networks, and planetary missions. Planetary missions to the solar system and the discovery of exoplanets and multiple systems provide a broad context for Earth’s studies, integrating studies and challenging models and theories. Here, we review developments in geodynamics, high pressure mineral physics, meteorite impacts, mass extinctions, and planetary sciences and in the emerging interconnections as fields develop.

2. Geodynamics and Earth’s Deep Interior

In the 1960s and early 1970s, development of plate tectonics provided a new paradigm for the Earth sciences, with Earth’s upper layer divided into several plates undergoing large-scale plate motions [1]. Plate tectonics integrated surface tectonic processes with the Earth’s interior and deep energy sources, linking magmatism, seismicity, mountain building, and metallogeny in a unified way. The theory integrated the rich long-held archive of geological and geophysical data on the continents with the more recently acquired information on the oceans, particularly on the mid-ocean ridges, fracture zones, and trenches [2–4]. Plate tectonics provides a kinematic framework building on a global synthesis of geologic mapping, structural geology, stratigraphy, paleontology, petrology, geochemistry, seismology, paleomagnetism, geodesy and marine geology, and geophysics.

In the past three decades, plate tectonics has proved highly successful, prompting multi- and interdisciplinary studies. Understanding how the planet works has however remained a challenge, with the dynamics of deep and surface processes, mechanisms, and energy sources only partly investigated. Key aspects of plate dynamics, mantle convection, hotspot magmatism, mantle layered structure, convection, core-mantle, intraplate deformation, vertical motions, polar wandering, and plate driving forces still remain only partly understood.

Plate tectonics provide a global model for the lithosphere, which is broken into several plates undergoing relative motion at plate boundaries (Figure 2(a)). Oceanic lithosphere is created at ridges and recycled back into the mantle at subduction zones. The advent of international and regional broadband seismological and GPS networks has provided instantaneous plate motion data. This has opened new ways to study plate kinematics, with improved spatial and temporal resolution. Plate models integrating geological and geodetic data are being constructed, which permit analyzing plate reorganizations for the past few million years and evaluating plate deformation and diffuse plate boundaries. The recent synthesis by DeMets et al. [5] incorporates 27 plates, including six small plates not directly linked to the ridge system, and gives a high resolution plate kinematic model (Figure 2(b)). Their results confirm the rigid plate assumption and provide constraints on plate deformation resulting from thermal contraction and wide plate boundaries.

Figure 2: The Earth’s lithosphere is divided into several tectonic plates that undergo relative motion. Plate boundaries are divergent boundaries (seafloor spreading ridges), convergent boundaries (subduction zones), and transform boundaries (transform faults). (a) Plate tectonic boundaries. Structural information on normal and reverse faults and volcanic centers is added (credits: NASA Earth Observatory and Goddard Space Flight Center website: http://earthobservatory.nasa.gov). (b) Global plate model incorporating 27 plates in a high resolution plate kinematic model (adapted from DeMets et al. [5]).

Over long time scales, plate motions have undergone major changes and plate reorganizations with ocean basins closing and opening, which relate to deep processes and mantle convection [6]. Geological estimates of plate motion using the marine magnetic anomalies, fracture zones, hotspot tracks, and paleomagnetic directions have been used to reconstruct plate kinematics for the past 200 Ma. Studies of oceanic plateaus, igneous provinces, orogenic belts, and volcanic arcs provide tight constraints on plate motions and mantle convection for the Phanerozoic and Precambrian, with formation of supercontinent assemblies and continental breakup [7]. The role of deep mantle structures in plate tectonics can be observed on the residual geoid long wavelength characteristics and shear wave velocity zones in the deep mantle and core-mantle boundary.

The challenge is how to use the improved resolution on plate kinematics for modeling plate dynamics [8]. The forces that control plate motion and the relation to deep processes in the mantle, the nature of hotspots, fate of subducted lithosphere, and processes at the core-mantle D′′ zone are in general poorly constrained. Earth’s deep structure, mineral composition, convection, high pressure/temperature physics, and energy sources remain as a major frontier [9, 10].

Advances are being made from seismological analyses imaging velocity anomalies, wave polarization, and seismic anisotropy features in the mantle and core [11]. Seismic wave attenuation anomalies have been documented with depth, which correlate with estimates from mantle viscosity from geodynamic modeling. Measurements of attenuation and other anelastic properties have been linked to rheological properties, which are investigated in theoretical models and laboratory experiments. The layered structure of Earth’s interior is characterized by increase of pressure and temperature, with variation of physical properties and mineralogy and phase changes. Pressure increases from about 24 GPa in the crust to 364 GPa in the inner core (Figure 3). Recently, physical and compositional structural mineral properties are being determined at increasing pressure and temperature using diamond-anvil cells, laser beams, noble gas graphite furnaces, and synchrotron sources. MgSiO-rich perovskite is the main constituent of the lower mantle down to 2900 km. This mantle mineral undergoes a phase transformation to denser postperovskite at core-mantle conditions, characterizing the physical properties at the D′′ layer. Iron and iron-silica alloys are investigated at simulated outer and inner core conditions, with pressures and temperatures up to 257 GPa and 2400 K [12] and 364 GPa and 5500 K [13]. Experiments on high pressure mineral physics are providing novel data on the mineralogy and physical properties like anelasticity and plasticity, which are coupled from first principles calculations in constraining phase transformations and depth variations [14–16].

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Figure 3: Density and seismic velocity variation with depth in Earth’s interior (adapted from Romanowicz [9]).

Computer modeling of convection permits testing different boundary conditions, property contrasts, and geometries, including those long explored of whole-mantle and double-layer convection. Dynamo modeling for geomagnetic field generation simulates short- and long-term variations observed at the surface in secular variation and regional anomalies, including polarity reversals. Thermal boundary conditions play major roles in dynamo behavior. Increasing computational power permits simulating fine mesh geometries with higher resolution. The field of geodynamic modeling, coupled to deep interior models for layered convection, mantle viscosity, and physical property contrast regional anomalies, has greatly expended in recent years showing large potential for further developments [17].

Plate boundaries are locations for active exchange interactions from the deep mantle to the surface, which manifest in seismicity, heat flow, and magmatic activity (Figure 4). Regional instrumental networks, geophysical surveys, and modeling on zones like the San Andreas transform fault in western United States, the Dead Sea and Anatolian faults in the Middle East, or the Honshu subduction zone in Japan are providing fresh high resolution data. Studies also address the economic implications, where significant mineral and energy resources concentrate at plate boundaries and related hazards associated with earthquakes and volcanic eruptions [18, 19]. Research on earthquakes, slow slip events, and volcanic eruptions provides enhanced understanding of mechanisms and developing new monitoring tools. Studies are addressing megathrust earthquakes like the Tokai-Oki magnitude 9.0 earthquake and the plate subduction process [20]. Active volcanoes present special challenges, particularly to model magma inside the conduits and deep connections in the mantle, which has prompted development of a range of methods of remote sensing, GPS, tiltmeters, broadband seismic networks, and integrated potential field and electromagnetic surveys. New tools being added include muons tomography exploiting secondary cosmic rays produced in the upper atmosphere with enhanced capabilities for imaging deep volcano structures [21, 22].

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Figure 4: (a) Seismicity and plate boundaries, with focal depth distribution. (b) Global seismic networks (adapted from Romanowicz [9]).

3. Impacts, Mass Extinctions, and Evolution

The evolution of life had been mostly studied from the fossil record, which provides evidence on past living organisms preserved along Earth’s history. Paleontological studies have built a broad picture of life evolution from the single-celled organisms in the Precambrian to the multicellular organism in the Phanerozoic, providing a spatial-temporal reference system incorporated into the geological time scale. The field moved from stratigraphic, fossilization, and taxonomic based studies to exploring the ecosystems, physiology, reproductive traits, organism diseases, climate and environmental interactions, and feedbacks. With the introduction of isotope geochemistry and molecular studies the paleobiology field is being expanded, becoming increasingly multi- and interdisciplinary.

The extinction rates have been climbing as a result of the effects of climate and environmental changes and anthropogenic activity. The global warming, ocean acidification, deforestation, and pollution are affecting the ecosystems, with the extinction of species in the land and marine realms. Over a longer time span from the last deglaciation at the Late Pleistocene and Holocene transition, a large number of species including many land and marine vertebrates has disappeared. The extinction rates and magnitude has increased interest in studying past extinction events, particularly those associated with the five mass extinctions in the Phanerozoic (Figure 5). Mass extinctions are characterized by being above the rates of background extinction levels, occurring over a relatively short time [23, 24]. Barnosky et al. [25] have analyzed the recent extinctions in a geological context and compared them with the past five events. Most of the species that have ever developed are extinct, so studies of extinction rates and mechanisms are critical for understanding the evolution processes.

Figure 5: Number of families as a function of geologic time, showing the five major extinction events marked by sharp biodiversity decrease (adapted from Raup and Sepkoski [23]).

The end-Cretaceous mass extinction, the second in severity in the Phanerozoic and most recent one, is being intensely studied. It affected significant numbers of species and genera, with extinction of the dinosaurs, pterosaurs, ammonites and numerous marine microorganisms, causing the disappearance of about 75% of the species. The mass extinction marks the end of the Mesozoic Era. The Cretaceous/Paleogene (K/Pg) boundary is recognized by a globally distributed thin clay layer (Figure 6), which represents the fine-grain-sized fraction of the ejecta from the Chicxulub impact [26–28]. The K/Pg boundary layer is a global stratigraphic marker, which permits unprecedented temporal resolution and lateral correlation of events.

Figure 6: Cretaceous/Paleogene (K/Pg) boundary sections for distal, intermediate, proximal, and very proximal sites. Schematic K/Pg boundary sections (b). (a) Distribution of K/Pg boundary sites (Schulte et al. [26]).

The K/Pg layer is a few millimeter-to-centimeters thick, formed by a basal spherulitic layer, representing parabolic-emplaced melted droplets or condensates from a high temperature ejecta cloud, and the clay representing the fine-grained ejecta emplaced in the upper stratosphere (Figure 6). In the Gulf of Mexico-Caribbean Sea region, it has a more complex structure with high-energy tsunami deposit and a high temperature layer. Analyses of the layer distribution, composition, and physical properties permit reconstructing the dynamics of the impact event. Studies of K/Pg boundary sections provide data on the climatic and environmental changes and effects on the biota. Studies include analyses on the extinct species, ecosystem disruption, surviving species, short- and long-term postimpact effects, recovery patterns, and diversification. The problem in interpreting the mechanisms of extinction and effects on the biota has been the precision needed in dating and correlation. Separating events on the scale of seconds to months involved in the impact event in the geologic record are a major challenge, which has sparked attempts in refining the dating methods and stratigraphy. The most recent analysis by Renne et al. [29] has reduced the uncertainties in dating the K/Pg boundary to within ~30 ka, which represents a sharp improvement in dating capabilities.

Studies on the K/Pg boundary, impact event, and mass extinction are expanding, addressing life evolution at short and long time scales. One of the processes investigated addresses the evolution on maximum body size of terrestrial mammals, which coexisted with dinosaurs during most of the Mesozoic. For about 140 Ma mammals coexisted with the dinosaurs, restricted to small body sizes and ecosystems. Following the extinction of dinosaurs, first the birds increased their size, including some large predators. Later, mammals started to diversify and increase their maximum body size during the Paleocene and early Eocene. Smith et al. [30] have analyzed the evolution of maximum body size for terrestrial mammals showing that the groups increase their body mass by the late Eocene, irrespective of the landmass.

The fossil record provides a punctuated view of life evolution, biased to certain geological settings, environments, and life forms that are more easily preserved. Dating and lateral correlation of rock strata present a further complication, with less resolution as we go back in time. High resolution stratigraphic methods, making use of multiproxy methods integrating statistical, spectral, and numerical simulation analyses, are being developed. Radiometric dating has improved, which is being applied combined with astronomical, magnetic polarity, and cyclostratigraphy, resulting in high resolution chronologies. The developments are applied to calibrating the geological time scale with increased precision.

Studies of the fossil record and evolution are closely related to the climatic and environmental factors, which are linked from the early beginnings in the Precambrian with the oxygenation of the atmosphere and oceans, the advent of the eukaryotes and evolution of life, and climate and environment during the Phanerozoic. Studies are focusing on early life forms, formation of the iron banded formations, global glaciations, and the construction of the life tree. New tools for climate reconstruction with increased high resolution are being developed using a wide range of biological, chemical, isotopic, and physical proxies. In Mexico and North and Central America, studies assess the effects, mechanisms, and interconnections of the Inter-tropical Convergence Zone latitudinal migration, North American monsoon, El Niño-Southern Oscillation, Pacific Decadal Oscillation, solar irradiance, and teleconnections [31, 32]. The studies are addressing climate evolution at different spatial and temporal scales, which are coupled with computational simulations and theoretical models for millennial, centennial to decadal resolution. Recent studies explore the links and influence of climatic and environmental factors on evolutionary patterns and the interconnections of the biosphere with climate [33].

A major development has come from the molecular clocks, which have significantly impacted methods to calibrate evolutionary time [34, 35]. Modeling tools for molecular tree analysis have rapidly evolved, providing estimates for branching events that are calibrated against the minimum ages from the fossil record. Improved understanding of the different genomes and rates of change has remained a major challenge in using molecular clocks to provide absolute dates. Given the advances in instrumentation and methods that are capable of providing vast amounts of data and processing power, the molecular clock will provide higher resolution in investigating evolutionary time. Multigene clocks applied to multitaxa are already giving unprecedented details in branching points, integrating phylogenetic reconstructions, the fossil record, and constraints on genome evolutionary rates [36].

Molecular analysis is well suited for studying macroevolutionary evolution, for instance, the appearance of eukaryotes, which in the fossil record appear at about 800 Ma when global changes in the oceans and climate were occurring. The molecular estimates for the early eukaryotic diversification are younger at around 1866 to 1679 Ma [36]. This older date is consistent with reports on eukaryotic microfossils, indicating a long time span in the diversification of the major eukaryotic lineages [33, 36]. Studies are addressing evolutionary traits at genomic level, investigating eukaryotic evolution over million-year periods across species. Organism complexity is related to genomic features such as cell type number, gene contents, protein length, proteome disorder, and protein interactivity, which are being quantified [37, 38]. In the 1.4 Ga evolution of eukaryotes, alternative splicing has steadily increased with organism complexity [38].

4. Planetary Sciences

Exploration of the solar system using Earth based multispectral remote sensing and space probes has opened new research frontiers. Planetary missions to the terrestrial planets and moons of the gas giant planets have provided data on the structure, surface morphology, magmatic activity, tectonic styles, and deep interiors.

Observations of the surfaces of the inner planets and moons show that they are characterized by craters of different sizes and morphologies. They have been formed by collision of asteroid and cometary fragments over time, from small sized impacts to the large peak ring and multiring basin impacts. Large impacts produce deep transient excavation cavities in the curst, fragmenting and removing large volumes of rock and redistributing crustal material. On Earth, the active tectonic environment and erosion have effectively erased the record of impacts, with a relatively small number of craters documented and only three large multiring basins [39]. The Chicxulub crater, with a ~200 km rim diameter formed at the K/Pg boundary, is the youngest of the multiring basins and the only one with the ejecta preserved [26, 27, 29]. The other two structures formed in Precambrian times: Sudbury at about 1.8 and Vredefort at about 2 Ga ago. Chicxulub crater is located in the Yucatan platform in the southern Gulf of Mexico. The structure is covered by carbonate sediments and is being investigated by geophysical methods and deep drilling (Figure 7) [40, 41].

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Figure 7: Chicxulub impact crater. (a) Gulf of Mexico and location of Chicxulub crater in the Yucatan platform. (b) Satellite interferometric radar image of Yucatan peninsula (credits: JPL-Caltech NASA), showing surface features associated with the buried crater structure. (c) Bouguer gravity anomaly of the Chicxulub crater (Sharpton et al. [40]). (d) Schematic lithological columns and lateral correlation for deep boreholes in the Chicxulub crater area, plotted as a function of relative distance to crater center (Urrutia-Fucugauchi et al. [27, 41]).

Impacts produce deformation at various depths, generating thermal anomalies and forming long-lived hydrothermal systems. The craters showing hydrothermal alteration are being investigated for manifestations of life forms, forming part of the exobiology programs. Studies of impact craters in the terrestrial record and elsewhere are enhancing understanding of these highly energetic phenomena in shaping planetary surfaces, including those in the asteroid belt.

Analysis of frequency, density, and size distribution of craters permits estimating the age of the planetary surfaces, with ancient surfaces marked by high density of craters, often including the large multiring basins [39]. The size-frequency crater relationships are also related to the geodynamics and deep structure. Plate tectonics appears restricted to Earth [10, 42]. Magmatic activity is observed in other bodies, including Mars, Venus, and Io. Mars lithosphere appears not being fragmented and under relative motion. Venus shows intense deformation and experienced a catastrophic resurfacing event about 500 Ma ago.

Evidence on the deep structure, thermal state, and convection comes from studies of meteorites, magnetic fields, and core dynamos. Meteorites have long been used for studying the origin and early stages of evolution of the planetary system (Figure 8). Analyses of chondrites and other primitive meteorites have documented the age of the first solids represented by refractory inclusions and chondrules, chemical composition of the solar nebula, and formation of planetesimals [43]. Studies are providing increasing resolution on the evolutionary stages (e.g., [43, 44]). Studies on chondrites and iron and stony-iron meteorites support that their planetesimals had differentiated iron cores capable of sustaining dynamo action for ~10 Ma periods [45–49]. The paleomagnetic record of main group pallasites supports the fact that they come from near the core-mantle boundary of differentiated planetesimals that sustained internal magnetic fields [47]. Partly differentiated planetesimals might have been relatively abundant in the early stages of the solar system [48]. Many were destroyed by energetic collisions, and a fraction of them are preserved in the asteroid belt. Recent analyses show that asteroid Vesta had a convecting iron core in the early stages [49].

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Figure 8: Schematic model of formation of chondrules and calcium-aluminium inclusions CAIs. (a) Protoplanetary disk. (b) Chondrule types with different morphologies and internal structures (adapted from Scott [43]). (c) Scanning electron microscopy images of individual chondrules from the Allende meteorite, showing the different morphologies, internal structures, and Fe, Ni, and S compositions. Numbers refer to laboratory sample identifications (Urrutia-Fucugauchi et al. [45]).

Planetary exploration is one of the most rapidly expanding frontiers in geophysics, with new data coming from the solar system missions and new exciting findings of exoplanets and planetary systems. The recent discoveries of exoplanets and multiple systems challenge the models for formation and early evolution of planetary systems based on observations of our solar system [50]. The large number of exoplanets discovered revives interest in planetary models with distinct formation zones for gas-icy giants and rocky planets within given regions of the accretion disk and models involving large-scale planet migration.

With increasing resolution and detection capacity, smaller Earth-sized planets are being detected. The Kepler space-based telescope mission is currently analyzing thousands of candidates, including several small mass planets. Recently, Quintana et al. [51] reported the finding of Kepler-186f, a 1.11 Earth-radius exoplanet in an orbit within the habitable zone around a M1-type dwarf star of the main sequence (Figure 9). Kepler-186f is the outermost planet of a five-planet system characterized by coplanar orbits. The multiplanet system is compatible with formation in a protoplanetary disk, with planets formed from accretion of local material and/or collisional growth of planetesimals. Numerical simulations conducted by Quintana and coauthors [51] for the Kepler-186 system show that too steep density configurations, with dense accretion disk close to the star, are required. These results suggest that planets underwent inward migration while forming or a late stage perturbation.

Figure 9: Schematic artistic representation of Kepler-186 multiple system compared with the inner solar system. Kepler-186 is a five-planet system located ~500 light-years away orbiting an M star half the Sun mass (Quintana et al. [51]) (credits: NASA Ames/SETI Institute/JPL-Caltech).

Detection methods focus mainly on large planets close to the star, so most discoveries are large gas planets in orbits close to their stars. Detecting small Earth-like planets remains a challenge. Robertson et al. [52] analyzed the system around the M dwarf Gliese 581 star, showing that stellar activity might cause interference resulting in false exoplanet detection. Their results show that the signal for GJ 581 g, one of the four exoplanets in the system, depends on the eccentricity assumed for the companion GJ 581 d.

A major challenge in studying exoplanets lies in constraining the mass, density, composition, and orbital parameters. Recent developments start to provide new tools and data. Rocky planets are expected to have smaller sizes than gas and icy planets, but additional observations are required, which can be explored from the star metallicity. Buchhave et al. [53] analyzed the abundance of elements heavier than hydrogen and helium for 405 exoplanet host stars, finding that the exoplanet sizes separate into three metallicity regions. The three populations are interpreted in terms of rocky, gas dwarf, and gas-icy giant exoplanets. Another field of intense scrutiny is the detection of atmospheres for the super-Earths, gas dwarfs, and icy-gas giants [54]. Recent studies using transmission spectroscopy data report absorption features giving details on the atmosphere properties, confirming clouds in a super-Earth [55]. Considering that a significant fraction of exoplanets so far detected range in size between Earth and Neptune, the new studies open an interesting research field.

Determining the orbital parameters and spin provides important constraints on the planet ambient characteristics. Many exoplanets detected show orbits close to the stars, which are easier to detect with current methods. Spectroscopy observations can provide data on the spin velocity, which has been recently reported for gas giant planet β Pictoris b [56]. The exoplanet is located far from the star, about twice the distance of Jupiter in our system, and is quite bright. The spin determination comes from (blue) shifted carbon monoxide spectral signals from the planet, which gives an estimate of 25 km/s. In the solar system, spin correlates with the mass, showing a broad trend with the exception of Mercury and Venus. The fast rotation velocity, about 2 and 50 times greater than Jupiter’s and Earth’s, fits well with the planet mass. The study adds an interesting tool for characterizing multiplanet systems, which can provide constraints for models of planetary formation.

Interest in extraterrestrial life, which for a long time remained limited to theoretical analyses, has led to studies of organisms in extreme environments. Studies of extremophile communities from the deep crust, ocean thermal vents, hyperarid deserts, or polar caps have expanded understanding on food webs, energy sources, reproductive strategies, and metabolic states. Planetary missions are being directed to extraterrestrial life searches. Several missions have been directed to Mars, since the Viking missions experiments have tested the properties of the soils and atmosphere looking for evidence on liquid water and organic compounds. Recent missions are expanding the characterization of surface liquid water, hydrothermal activity, organic compounds, and fossil clues. New missions and spectroscopy observations use remote sensing clues of life activity in the planetary atmospheres.

Until the mid-1990s, the only planetary system known was our own. Models for evolution of planetary nebula predicted the formation of planets from planetary disks, but no observational evidence was available. The recent reports of hundreds of exoplanets and multiple planet systems and the observations on their sizes, orbits, and star characteristics are drastically changing and expanding theories and models for formation of planets and planetary systems [57–60].

5. Conclusions

New tools like the Earth observation satellite network, the global positioning system, planetary missions, high pressure/temperature experiments, high resolution tomography, and high performance computing play a major role in expanding research frontiers in geophysics. Increased interest in understanding Earth processes and new developments in instrumentation, modeling, and observation capabilities also comes from population growth and demographic changes, which increase global demand for minerals, water, and energy resources, resulting in pollution, land use changes, deforestation, environmental degradation, organism extinction, changes in atmospheric gas composition, and global warming. In this context, understanding Earth’s subsystems of the atmosphere, oceans, continents, ionosphere, magnetosphere, biosphere, and deep interior, their interconnections, cycles, spatio-temporal scales, and feedback mechanisms has become a major priority. The anthropogenic induced changes are comparable to those caused by geologic forces on the planet, highlighting the importance of integrated research. This has prompted global approaches in Earth system science and development of research fields, many of them at cross-disciplinary borders like biogeosciences, environmental geophysics, exobiology, and planetary sciences.

In a broad general context, the developments in high performance computing power, personal computers, telecommunications, electronics, and advent of the internet are profoundly changing the scientific research enterprise. The developments touch practically every area related to research with electronic databases, publications, electronic archives, search engines, software, and personal and group interactions. The capacity for analyzing massive data sets using supercomputers and computer networks facilitates using numerical methods and complex simulations. High performance computing allows modeling of the complex climate system, core and mantle tomography, Earth observational satellite multispectral data, or exoplanet detection systems with the massive data sets from the space-telescope Kepler and other search missions.

Studies in widely different fields are interconnected with the recent developments, opening bridges across previously separated endeavors. Studies on the origin and evolution of the solar system are linked to the new areas of planetary sciences, which challenge current models opening new questions. Most of the exoplanets discovered are in the size range between Earth and Neptune, for which there are no analogs in the solar system. Studies of the structure and properties, orbital characteristics, and formation mechanisms for the super-Earths and gas giants are giving fresh insights on planetary evolution [58]. Studies are addressing finer details in the characteristics of exoplanets in addition to size, orbit, and mass, such as the spin, surface temperature, and presence and composition of atmospheres and clouds [59, 60]. The mass-spin relation in the solar system is related to the breakup velocity and impacts added angular momentum. The estimation of the fast spin for β Pictoris b, which fits with the trend for fast spin and large mass, opens the link of impacts in the formation of planets [57, 59]. β Pictoris b is a young planet still contracting and cooling, towards a size comparable to Jupiter. Determination of the spin characteristics for a larger group of exoplanets will allow investigating how planets form and evolve in different protoplanetary disks environments.

Exoplanet research and planetary missions connect with investigation of the cratering record on Earth and in other bodies of the solar system, including the large impacts during the early stages of planet formation. Satellites in the solar system show different characteristics of the rocky and gas-icy planets, with small satellites in large planets and larger satellites in small planets. Studies on the tectonics and deep structure on Earth are now related to planetary research on the planet interiors, planet formation models, and thermal states [42]. Results from high pressure and temperature mineral physics [11–15] relate and constrain models of formation of super-Earth and giant icy-gas exoplanets [51–60], as well as the planets in the solar system [50]. We have similar links between studies of life on extreme terrestrial environments, origin, and evolution of life in the young Earth and studies of exobiology [61]. Studies are uncovering relationships and exploring new questions and interconnections.

Competing Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

The authors thank Ana Escalante and Miguel Angel Diaz for assistance with the figures. This study forms part of National University of Mexico Programs on the Chicxulub Impact, the Cretaceous/Paleogene Boundary, and MeteorPlan. Partial support comes from Papiit IG-101115 and Conacyt grants.

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