Terrestrial Bodies Research Articles

Computational Millimeter Wave Imaging: Problems, progress, and prospects

Imaging using millimeter waves (mmWs) has many advantages and applications in the defense, security, and aviation markets. All terrestrial bodies emit mmW radiation, and these wavelengths are able to penetrate smoke, blowing dust or sand, fog/clouds/marine layers, and even clothing. However, there are many obstacles to imaging in this spectrum that have to be overcome before mmW imaging systems can be successfully realized for surveillance and defense applications. Recent developments in computational imaging have the potential to significantly improve capabilities of mmW imaging systems. Our article provides an overview of computational imaging and its implication to mmW imaging in various operation modes. We discuss the merits and drawbacks of available computational mmW imaging approaches and identify avenues of research in this rapidly evolving field.

MAPPING OF INNER AND OUTER CELESTIAL BODIES USING NEW GLOBAL AND LOCAL TOPOGRAPHIC DATA DERIVED FROM PHOTOGRAMMETRIC IMAGE PROCESSING

New estimation of fundamental geodetic parameters and global and local topography of planets and satellites provide basic coordinate systems for mapping as well as opportunities for studies of processes on their surfaces. The main targets of our study are Europa, Ganymede, Calisto and Io (satellites of Jupiter), Enceladus (a satellite of Saturn), terrestrial planetary bodies, including Mercury, the Moon and Phobos, one of the Martian satellites. In particular, based on new global shape models derived from three-dimensional control point networks and processing of high-resolution stereo images, we have carried out studies of topography and morphology. As a visual representation of the results, various planetary maps with different scale and thematic direction were created. For example, for Phobos we have produced a new atlas with 43 maps, as well as various wall maps (different from the maps in the atlas by their format and design): basemap, topography and geomorphological maps. In addition, we compiled geomorphologic maps of Ganymede on local level, and a global hypsometric Enceladus map. Mercury’s topography was represented as a hypsometric globe for the first time. Mapping of the Moon was carried out using new images with super resolution (0.5-1 m/pixel) for activity regions of the first Soviet planetary rovers (Lunokhod-1 and -2). New results of planetary mapping have been demonstrated to the scientific community at planetary map exhibitions (Planetary Maps Exhibitions, 2015), organized by MExLab team in frame of the International Map Year, which is celebrated in 2015-2016. Cartographic products have multipurpose applications: for example, the Mercury globe is popular for teaching and public outreach, the maps like those for the Moon and Phobos provide cartographic support for Solar system exploration.

Урожайность топинамбура (Helianthus Tuberosus L.) в условиях Таджикистана

Jerusalem artichoke (Helianthus tuberosus L.) is a perennial herbaceous plant height from 40 cm to 2.5 m high with erect branched, leafy stem. The length of the growing season is 4.5–5 months. The yield of tubers in average 15 t/ha, the total productivity of terrestrial bodies – 70...90 t/ha. In Tajikistan, the Jerusalem artichoke began to be cultivated in 40–50 years of the last century. In the conditions of the Gissar valley at an experimental plot of the Institute of botany, physiology and plant genetics of the Academy of Sciences of the Republic of Tajikistan, located in the Eastern part of Dushanbe at the altitude of 840 m above sea level, and carried out the planting of Jerusalem artichoke tubers in midApril. In the conditions of Rasht valley (Jirgatol district at altitudes of 2100 and 2700 m above sea level and the Rasht district, at an altitude of 2300 m above sea level) planting tubers of Jerusalem artichoke was conducted in the third week of may. Identification of the general size a biomass sun artichoke on the irrigation fields of Gissar and Rasht valleys fluctuates within from 66.5 to 94.2 t/hec. and on rein field from 30.4 to 72.5 t/hec., yield of tubers from 24.95 to 38.4 t/hec. on the irrigation fields and from 11.85 to 22.95 t/hec. on rein fields. On the Jerusalem artichoke average the biomass on the irrigation fields makes 78.8 t/hec. and on rein fields 47.4 t/hec, and a crop of tubers accordingly 30.63 and 15.73 t/hec. that testifies to efficiency of cultivation sun artichoke in irrigation and rein fields of our republic. The irrigation promote increase of biomass yield of american artichoke on 30.4 t/hec. (64.1 %), yield of tubers – on 14.9 t/hec.( 94.7 %) in comparison with cultivation without irrigation.

A comparative analysis of the magnetic field signals over impact structures on the Earth, Mars and the Moon

An improved description of magnetic fields of terrestrial bodies has been obtained from recent space missions, leading to a better characterization of the internal fields including those of crustal origin. One of the striking differences in their crustal magnetic field is the signature of large impact craters. A comparative analysis of the magnetic characteristics of these structures can shed light on the history of their respective planetary-scale magnetic dynamos. This has motivated us to identify impact craters and basins, first by their quasi-circular features from the most recent and detailed topographic maps and then from available global magnetic field maps. We have examined the magnetic field observed above 27 complex craters on the Earth, 34 impact basins on Mars and 37 impact basins on the Moon. For the first time, systematic trends in the amplitude and frequency of the magnetic patterns, inside and outside of these structures are observed for all three bodies. The demagnetization effects due to the impact shock wave and excavation processes have been evaluated applying the Equivalent Source Dipole forward modeling approach. The main characteristics of the selected impact craters are shown. The trends in their magnetic signatures are indicated, which are related to the presence or absence of a planetary-scale dynamo at the time of their formation and to impact processes.The low magnetic field intensity at center can be accepted as the prime characteristic of a hypervelocity impact and strongly associated with the mechanics of impact crater formation. In the presence of an active internal field, the process of demagnetization due to the shock impact is associated with post-impact remagnetization processes, generating a more complex magnetic signature.

Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

Recent planetary space missions, new experimental data, and advanced numerical techniques have helped to improve our understanding of the deep interiors of the terrestrial planets and moons. In the present review, we summarize recent insights into the state and composition of their iron (Fe)-rich cores, as well as recent findings about the magnetic field evolution of Mercury, the Moon, Mars, and Ganymede. Crystallizing processes in iron-rich cores that differ from the classical Earth case (i.e., Fe snow and iron sulfide (FeS) crystallization) have been identified and found to be important in the cores of terrestrial bodies. The Fe snow regime occurs at pressures lower than that in the Earth’s core on the iron-rich side of the eutectic, where iron freezes first close to the core–mantle boundary rather than in the center. FeS crystallization, instead, occurs on the sulfur-rich side of the eutectic. Depending on the core temperature profile and the pressure range considered, FeS crystallizes either in the core center or close to the core–mantle boundary. The consequences of the various crystallizing mechanisms for core dynamics and magnetic field generation are discussed. For the Moon, revised paleomagnetic data obtained with advanced techniques suggest a peculiar history of its internal dynamo, with an early strong field persisting between 4.25 and 3.5 Ga, and subsequently a much weaker field. In addition, the long-lasting dynamo and the possible presence of an inner core, as inferred from a revised interpretation of Apollo seismic data, suggest core crystallization as a viable process of magnetic field generation for a substantial period during lunar evolution. The present-day magnetic fields of Mercury and Ganymede (if they occur on the iron-rich side of the Fe–FeS eutectic) and the related dynamo action are likely generated in the Fe snow regime and seem to be recent features. An earlier dynamo in Mercury would have been powered differently. For Mercury, MESSENGER data further suggest core formation under reducing conditions that may have resulted in an Fe–S–Si composition, further complicating the core crystallization process. Mars, with its early and strong paleo-field, likely has not yet started to freeze out an inner iron core.

Statistical analysis of mineral diversity and distribution: Earth's mineralogy is unique

Earth's mineralogical diversity arises from both deterministic processes and frozen accidents. We apply statistical methods and comprehensive mineralogical databases to investigate chance versus necessity in mineral diversity-distribution relationships. Hundreds of mineral species, including most common rock-forming minerals, distinguish an “Earth-like” planet from other terrestrial bodies. However, most of Earth's ∼5000 mineral species are rare, known from only a few localities. We demonstrate that, in spite of deterministic physical, chemical, and biological factors that control most of our planet's mineral diversity, Earth's mineralogy is unique in the cosmos.

Early stages of core segregation recorded by Fe isotopes in an asteroidal mantle

Ureilite meteorites are achondrites that are debris of the mantle of a now disrupted differentiated asteroid rich in carbon. They provide a unique opportunity to study the differentiation processes of such a body. We analyzed the iron isotopic compositions of 30 samples from the Ureilite Parent Body (UPB) including 29 unbrecciated ureilites and one ureilitic trachyandesite (ALM-A) which is at present the sole large crustal sample of the UPB. The δ56Fe of the whole rocks fall within a restricted range, from 0.01 to 0.11‰, with an average of +0.056±0.008‰, which is significantly higher than that of chondrites. We show that this difference can be ascribed to the segregation of S-rich metallic melts at low degrees of melting at a temperature close to the Fe–FeS eutectic, and certainly before the onset of the melting of the silicates (<1100°C), in agreement with the marked S depletions, and the siderophile element abundances of the ureilites. These results point to an efficient segregation of S-rich metallic melts during the differentiation of small terrestrial bodies.

Mid-infrared optical constants of clinopyroxene and orthoclase derived from oriented single-crystal reflectance spectra

We have determined the mid-IR optical constants of one alkali feldspar and four pyroxene compositions in the range of 250–4000 cm−1. Measured reflectance spectra of oriented single crystals were iteratively fit to modeled spectra derived from classical dispersion analysis. We present the real and imaginary indices of refraction ( n and k ) along with the oscillator parameters with which they were modeled. While materials of orthorhombic symmetry and higher are well covered by the current literature, optical constants have been derived for only a handful of geologically relevant monoclinic materials, including gypsum and orthoclase. Two input parameters that go into radiative transfer models, the scattering phase function and the single scattering albedo, are functions of a material’s optical constants. Pyroxene is a common rock-forming mineral group in terrestrial bodies as well as meteorites and is also detected in cosmic dust. Hence, having a set of pyroxene optical constants will provide additional details about the composition of Solar System bodies and circumstellar materials. We follow the method of Mayerhofer et al. (2010), which is based on the Berreman 4 × 4 matrix formulation. This approach provides a consistent way to calculate the reflectance coefficients in low-symmetry cases. Additionally, while many models assume normal incidence to simplify the dispersion relations, this more general model applies to reflectance spectra collected at non-normal incidence.

Viscosity of liquid fayalite up to 9 GPa

The viscosity of liquid fayalite (Fe2SiO4) was determined up to 9.2GPa and 1850°C using in situ falling sphere viscometry and X-ray radiography imaging. The viscosity of liquid fayalite was found to decrease both along the melting curve and an isotherm, therefore temperature is thought to have little effect on liquid fayalite viscosity at high pressure. The results are in contrast with previous studies on depolymerised silicate melts which found viscosity to increase with pressure. In accordance with recent in situ structural measurements on liquid fayalite, the viscosity decrease is likely a result of the increase in Fe–O coordination with pressure. The results show that liquid silicate viscosities need to be considered on an individual basis and can be strongly dependent on the melt structure and composition. This has important implications for models of planetary differentiation. In particular, terrestrial bodies with high Fe contents and reducing mantle conditions are likely to have had very mobile melts at depth.

Long‐lived explosive volcanism on Mercury

AbstractThe duration and timing of volcanic activity on Mercury are key indicators of the thermal evolution of the planet and provide a valuable comparative example for other terrestrial bodies. The majority of effusive volcanism on Mercury appears to have occurred early in the planet's geological history (~4.1–3.55 Ga), but there is also evidence for explosive volcanism. Here we present evidence that explosive volcanism occurred from at least 3.9 Ga until less than a billion years ago and so was substantially more long‐lived than large‐scale lava plains formation. This indicates that thermal conditions within Mercury have allowed partial melting of silicates through the majority of its geological history and that the overall duration of volcanism on Mercury is similar to that of the Moon despite the different physical structure, geological history, and composition of the two bodies.

The chronostratigraphy of protoplanet Vesta

In this paper we present a time-stratigraphic scheme and geologic time scale for the protoplanet Vesta, based on global geologic mapping and other analyses of NASA Dawn spacecraft data, complemented by insights gained from laboratory studies of howardite–eucrite–diogenite (HED) meteorites and geophysical modeling. On the basis of prominent impact structures and their associated deposits, we propose a time scale for Vesta that consists of four geologic time periods: Pre-Veneneian, Veneneian, Rheasilvian, and Marcian. The Pre-Veneneian Period covers the time from the formation of Vesta up to the Veneneia impact event, from 4.6Ga to >2.1Ga (using the asteroid flux-derived chronology system) or from 4.6Ga to 3.7Ga (under the lunar-derived chronology system). The Veneneian Period covers the time span between the Veneneia and Rheasilvia impact events, from >2.1 to 1Ga (asteroid flux-derived chronology) or from 3.7 to 3.5Ga (lunar-derived chronology), respectively. The Rheasilvian Period covers the time span between the Rheasilvia and Marcia impact events, and the Marcian Period covers the time between the Marcia impact event until the present. The age of the Marcia impact is still uncertain, but our current best estimates from crater counts of the ejecta blanket suggest an age between ∼120 and 390Ma, depending upon choice of chronology system used. Regardless, the Marcia impact represents the youngest major geologic event on Vesta. Our proposed four-period geologic time scale for Vesta is, to a first order, comparable to those developed for other airless terrestrial bodies.

Moon, Mars, Mercury: Basin formation ages and implications for the maximum surface age and the migration of gaseous planets

Basin formation ages for Moon, Mars and Mercury are determined by cratering statistics, compared and evaluated with respect to their maximum surface ages and available isotope ages, and two possible Solar System evolution models. Both Mars and Mercury appear to have undergone significant resurfacing, so that at least the first 200–400 million years are not recorded on their surfaces. Basin frequency and crater frequencies below 150 km indicate that the Moon has the oldest surface, Mercury has an intermediate age, and Mars has the youngest preserved terrain. An offset between the basin size-frequency distribution, the smaller crater size-frequency distribution and the main belt asteroid size-frequency distribution is observed in all three cases, suggesting an age difference of about 150 Ma between basin and smaller crater distribution-based ages. I interpreted this in terms of lack of understanding of the basin formation process, and suggest that one possible explanation for the apparently under-representative basin frequency could be a different (lower) average impact velocity compatible with the ‘Nice’ flux model. The basin formation pattern derived with the standard monotonically decaying or the sawtooth-like Nice-model flux does not reveal a coherent picture according to the late heavy bombardment idea. This is here attributed to an incomplete understanding of the cratering rate ratios between the planetary bodies considered here. Because of the Moon's unique formation history, I also suggest that it is questionable whether the Moon is a suitable analogue for the formation, evolution and cratering record of the other terrestrial bodies.

Formation and Suppression of Strike–Slip Fault Systems

Strike–slip faults are a defining feature of plate tectonics, yet many aspects of their development and evolution remain unresolved. For intact materials and/or regions, a standard sequence of shear development is predicted from physical models and field studies, commencing with the formation of Riedel shears and culminating with the development of a throughgoing fault. However, for materials and/or regions that contain crustal heterogeneities (normal and/or thrust faults, joints, etc.) that predate shear deformation, kinematic evolution of strike–slip faulting is poorly constrained. We present a new plane-stress finite-strain physical analog model developed to investigate primary deformation zone evolution in simple shear, pure strike–slip fault systems in which faults or joints are present before shear initiation. Experimental results suggest that preexisting mechanical discontinuities (faults and/or joints) have a marked effect on the geometry of such systems, causing deflection, lateral distribution, and suppression of shears. A lower limit is placed on shear offset necessary to produce a throughgoing fault in systems containing preexisting structures. Fault zone development observed in these experiments provides new insight for kinematic interpretation of structural data from strike–slip fault zones on Earth, Venus, and other terrestrial bodies.

ASPITZERSEARCH FOR TRANSITS OF RADIAL VELOCITY DETECTED SUPER-EARTHS

Unlike hot Jupiters or other gas giants, super-Earths are expected to have a wide variety of compositions, ranging from terrestrial bodies like our own to more gaseous planets like Neptune. Observations of transiting systems, which allow us to directly measure planet masses and radii and constrain atmospheric properties, are key to understanding the compositional diversity of the planets in this mass range. Although Kepler has discovered hundreds of transiting super-Earth candidates over the past four years, the majority of these planets orbit stars that are too far away and too faint to allow for detailed atmospheric characterization and reliable mass estimates. Ground-based transit surveys focus on much brighter stars, but most lack the sensitivity to detect planets in this size range. One way to get around the difficulty of finding these smaller planets in transit is to start by choosing targets that are already known to contain super-Earth sized bodies detected using the radial velocity technique. Here we present results from a Spitzer program to observe six of the most favorable RV detected super-Earth systems, including HD 1461, HD 7924, HD 156668, HIP 57274, and GJ 876. We find no evidence for transits in any of their 4.5 micron flux light curves, and place limits on the allowed transit depths and corresponding planet radii that rule out even the most dense and iron-rich compositions for these objects. We also observed HD 97658, but the observation window was based on a possible ground-based transit detection (Henry et al. 2011) that was later ruled out; thus the window did not include the predicted time for the transit detection recently made by MOST (Dragomir et al. 2013).

Lithium systematics in howardite–eucrite–diogenite meteorites: Implications for crust–mantle evolution of planetary embryos

We present lithium (Li) abundances and isotope compositions in a suite of howardites, eucrites and diogenites (HEDs). These meteorites most likely originated from asteroid Vesta and were delivered to Earth by a series of independent impact events. The Li concentrations show striking differences between Li-poor diogenites plus cumulate eucrites and Li-enriched eucrites whilst howardites have Li abundances intermediate between eucrites and diogenites. Contrary to Li elemental inter-group differences, Li isotope compositions are irresolvable among these individual groups of HED meteorites despite their wildly distinct petrography, attesting to insignificant Li isotope fractionation during formation of a thick basaltic crust by melting of the Vestan mantle. The mean Li isotope composition of Bulk Silicate Vesta is estimated at 3.7±0.6‰ (1σ), intermediate to that of the Earth versus Mars and Moon but identical with these terrestrial bodies within uncertainty. This further validates largely homogeneous inner Solar System solids from the Li isotope perspective and supports the lack of loss of moderately volatile elements from planetary embryos during their magmatic histories because Li does not follow depletion trends inferred from more volatile elements. Pasamonte eucrite has the same Li isotope composition as other eucrites although it may not be directly linked to Vesta. These observations are also important for generating Li elemental and isotope signatures in juvenile basaltic crusts of large terrestrial planets and numerous planetary embryos in the early Solar System. A combination of CV+L chondrites may be less suitable for building Vesta from Li perspective but this may face sampling bias of available data and only further analyses may resolve this issue. Alternatively, significant shift of ∼1‰ towards heavier Li isotope compositions must have occurred during thermal processing of CV+L (2.2–2.8‰) mixture in order to account for the observed Li isotope systematics in HED meteorites. No correlation is observed between Li versus Zn, Fe or Si isotopes, respectively, implying unrelated processes of forming stable isotope variations observed in HED meteorites.

Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies

Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3.

Analysis of magnetic satellite data to infer the mantle electrical conductivity of telluric planets in the solar system

Space missions launched to study the solar system planets generally involve a magnetometer in the scientific payload. The magnetic data may be used to infer the electrical conductivity of a planet's mantle using electromagnetic induction theory. The application of induction analysis on terrestrial bodies of the solar system other than the earth is challenging because of little information available about the external inducing sources. Here, we present a method to analyze magnetic data from these space missions that determines the geometry of the dominant external inducing magnetic field and deals with the inherent gaps in the satellite magnetic time series. We tested the approach on Earth synthetic satellite data generated to prepare the ESA magnetic mission Swarm and demonstrated the feasibility for recovering the 1-D conductivity part of the model used to generate these data. The analysis of real data from the Danish Ørsted magnetic mission provided satisfactory conductivity profiles of the Earth's mantle.

Quantifying the Martian Geochemical Reservoirs: An Interdisciplinary Perspective

The planet Mars has fascinated humanity since antiquity, a fascination that persists to the present-day, fuelled by the enticing possibility that the conditions necessary for life may once have existed there, and perhaps continue to exist to the present day. Indeed, comparative planetology of terrestrial bodies large enough to retain an atmosphere is a key to understanding the formation of our own planet and the physical and chemical conditions that led to the emergence and the development of life. In more general terms, the study of rocky bodies of the solar system also provides a context for planetary formation as a whole, shedding light on the geochemical similarities and differences between the principal objects of the inner solar system, as well as the cores of the outer planets and many of their satellites. However, it was not until the advent of space-based exploration in the 1960s that quantification of the geochemical characteristics of our planetary neighbours first became possible. Indeed, our knowledge of Mars changed dramatically when Mariner 4 took the first close-up pictures in July 1965, observing a highly cratered arid landscape. In 1976 the Viking orbiters and landers provided ground-breaking insight into surface morphology and the chemistry of the soil and atmosphere on Mars, data that also led to confirmation that the ShergottiteNakhlite-Chassignite group of meteorites (SNC) most probably have a martian origin. This

Direct measurement of hydroxyl in the lunar regolith and the origin of lunar surface water

Remote sensing discoveries of hydroxyl and water on the lunar surface have reshaped our view of the distribution of water and related compounds on airless bodies such as the Moon. The origin of this surface water is unclear, but it has been suggested that hydroxyl in the lunar regolith can result from the implantation of hydrogen ions by the solar wind. Here we present Fourier transform infrared spectroscopy and secondary ion mass spectrometry analyses of Apollo samples that reveal the presence of significant amounts of hydroxyl in glasses formed in the lunar regolith by micrometeorite impacts. Hydrogen isotope compositions of these glasses suggest that some of the observed hydroxyl is derived from solar wind sources. Our findings imply that ice in polar cold traps could contain hydrogen atoms ultimately derived from the solar wind, as predicted by early theoretical models of water stability on the lunar surface. We suggest that a similar mechanism may contribute to hydroxyl on the surfaces of other airless terrestrial bodies where the solar wind directly interacts with the surface, such as Mercury and the asteroid 4-Vesta.

Hydrous melting of the martian mantle produced both depleted and enriched shergottites

The search for water in our solar system is one of the primary driving forces for planetary science and exploration because water plays an important role in many geologic processes and is required for biologic processes as we currently understand them. Excluding Earth, Mars is the most promising destination in the inner solar system to find water, as it is undoubtedly responsible for shaping many geomorphologic features observed on the present-day martian surface; however, the water content of the martian interior is currently unresolved. Much of our information about the martian interior comes from studies of the basaltic martian meteorites (shergottites). In this study we examined the water contents of magmatic apatites from a geochemically enriched shergottite (the Shergotty meteorite) and a geochemically depleted shergottite (the Queen Alexandria Range 94201 meteorite). From these data, we determined that there was little difference in water contents between the geochemically depleted and enriched shergottite magmas. The water contents of the apatite imply that shergottite parent magmas contained 730–2870 ppm H 2 O prior to degassing. Furthermore, the martian mantle contains 73–290 ppm H 2 O and underwent hydrous melting as recently as 327 Ma. In the absence of plate tectonics, the presence of water in the interior of Mars requires planetary differentiation under hydrous conditions. This is the first evidence of significant hydrogen storage in a planetary interior at the time of core formation, and this process could support elevated H abundances in the interiors of other terrestrial bodies like the Moon, Mercury, Venus, large differentiated asteroids, and Earth.