Anorthosite is a plutonic igneous rock composed almost entirely of plagioclase feldspar. Telluric planets may initially develop a primary anorthositic crust before lithospheric recycling processes ...commence. Non-primary anorthosite forms as a consequence of accumulation of plagioclase that crystallizes from basaltic or primitive mafic/ultramafic magma. Here we show that fractional crystallization modeling of parental magma compositions similar to basalt identified on Venus can yield plagioclase with anorthite contents typical of non-primary anorthosites of Earth. Using terrestrial anorthosite typology, we conclude that analogues of Archean megacrystic anorthosite, layered mafic intrusion anorthosite, and anorthosite inclusions are likely to be present within the crust of Venus. Proterozoic massif-type anorthosite, if present, would likely be restricted to the highland terranes of Ishtar Terra and Ovda Regio whereas oceanic anorthosites are unlikely to be present. Furthermore, our results indicate that the leucite-rich cumulate rock known as italite may also exist within the Venusian crust.
•Analogues of Archean megacrystic and LMI anorthosites likely exist on Venus.•Proterozoic massif-type anorthosite may exist within the thickest crust of Venus.•Oceanic anorthosites are unlikely to be present on Venus.•The Venera 13 models indicate that italite could be present on Venus.
Preobrazba žanra je bila rdeča nit v Ovidijevih Ljubeznih, v pričujoči članek pa prikazuje, da je ta tema osrednjega pomena tudi v Rimskem koledarju, v Ovidijevem »večjem delu«. Žanr ajtiološke ...elegije je v tej pesnitvi Ovidij preobrazil tako, da je v ajtiologije rimskih praznikov vpletel epske elemente, ljubezensko-erotične ajtiologije in mimus. Čeprav Ovidijev pesniški lik še naprej pesni pod vplivom boginje ljubezni Venere, pričujoči članek pokaže, da je v Rimskem koledarju Ovidijeva prava ljubezen Flora. Ovidijev pesniški lik je privzel način življenja v znamenju Flore, veseli se mimov, razpuščenega uživanja v nočnih gostijah, vina in pesniškega ustvarjanja. V svoji preobrazbi žanra Ovidij kreativno sledi literarnim vzorom iz rimskega imperija, predvsem Kalimahovim Izvorom. V procesu preobrazbe elegičnega žanra v Florino elegijo Ovidij poudari že obstoječe politične konotacije rimske elegije tako, da se distancira od Avgustovih vrednot, predvsem spolne morale.
Observations of planetary magnetic fields provide fundamental insights into the origin and evolution of terrestrial planets. However, whether Venus ever hosted a dynamo is unknown. Here we show that ...crustal remanent magnetism is a potentially observable consequence of an ancient Venusian dynamo, in contrast to previous studies that dismissed this possibility. Past spacecraft measurements only exclude crustal magnetization near the Venera 4 landing site and northward of 50° South latitude for >150‐km coherence scales and strong magnetization intensities. Magnetite grains with sizes commonly observed in volcanic rocks can retain thermoremanent magnetism at Venusian conditions for >1 billion years. Depths to the Curie temperature of magnetite are ~5–40 km and typically less than predicted crustal thicknesses at our analyzed localities. Aerial platforms could detect expected magnetizations at horizontal scales similar to the ~50‐km operating altitude. Any detection would validate models of planetary accretion, geologic processes, and climate history.
Plain Language Summary
Unlike Earth, Venus has no global magnetic field generated by churning fluid in its metallic core. Models indicate that Venus may have hosted an Earth‐strength field until at least a billion years ago—roughly the average surface age—if giant impacts mixed the core during planetary formation. Without energetic impacts, models suggest that chemical layering in the core would always suppress fluid motions and thus a dynamo. Searching for ancient magnetized rocks (already discovered on Moon, Mars, and Mercury) would test these models. Venus has a very hot surface, which decreases the stability of ancient magnetization and has caused pessimism about the chances of obtaining useful data. However, we found that common minerals such as magnetite are magnetically stable for billions of years at the current surface temperature. Enough crust could remain magnetized to produce signals detectable by orbiters at low altitudes or, ideally, aerial platforms floating in the atmosphere.
Key Points
Whether Venus once hosted a dynamo‐generated magnetic field has broad implications for the accretion and evolution of terrestrial planets
Despite high surface temperatures on Venus, magnetite and hematite grains may retain thermoremanent magnetization for >1 billion years
Crust magnetized to depths of >1‐5 km could produce signals detectable by an aerial platform operating at ~50‐km altitude
Archaeoseismological evidence of a strong earthquake, which probably occurred a year before the 252 CE Mt. Etna eruption, has been uncovered at Santa Venera al Pozzo site, located near to Acireale, ...along the lower eastern flank of the volcano. The site, known for its remarkable and peculiar hydrothermal fluids emissions exploited for thermal uses since the Greek and Roman age, has been investigated through a multidisciplinary approach by integrating archaeoseismological observations with geological and geochemical surveys. Analysis of the observed damage and deformation at the site suggest a capable fault zone through the area. Geochemical and geological surveys were performed in and around the site and have revealed anomalies of soil CO2 efflux along an known active fault and likely also along some unmapped hidden faults. The chemical and isotopic composition of the emitted fluids suggests that these have not a volcanic origin, but they could be related with a deep tectonic system. The data presented in this paper suggest the occurrence of both exposed and hidden active faults in the area of Santa Venera al Pozzo, which could be linked to the seismic activity that damaged the historical site.
•The Santa Venera al Pozzo site shows damage probably ascribed to the 251 CE earthquake as documented by historical sources.•The site is near important tectonic faults and it is known for its thermal gas-rich water springs.•Chemical and isotopic data of springs local fluids point to their typical geothermal origin, without any fresh magmatic input.•Anomalies of soil CO2 emissions reveal hidden faults whose trend is compatible with regional tectonics.
•Shows at what rate ground motion of different amplitudes appears at 3 terrestrial sites.•Compares with Apollo, Viking, Venera and Huygens data.•Guides expectations for instrumentation on planetary ...landers.•Recurrence rate plots serve as a useful communication tool to non-seismologists.
We determine the recurrence rates of ground motion events as a function of sensed velocity amplitude at several terrestrial locations, and make a first interplanetary comparison with measurements on the Moon, Mars, Venus and Titan. This empirical approach gives an intuitive order-of-magnitude guide to the observed ground motion (including both tectonic and ocean- and atmosphere-forced signals) of these locations as a guide to instrument expectations on future missions, without invoking interior models and specific sources: for example a Venera-14 observation of possible ground motion indicates a microseismic environment mid-way between noisy and quiet terrestrial locations. Quiet terrestrial regions see a peak velocity amplitude in mm/s roughly equal to 0.3*N(-0.7), where N is the number of “events” (half-hour intervals in which a given peak ground motion is exceeded) observed per year. The Apollo data show endogenous seismic signals for a given recurrence rate that are typically about 10,000 times smaller in amplitude than a quiet site on Earth, although local thermally-induced moonquakes are much more common. Viking data masked for low-wind periods appear comparable with a quiet terrestrial site, whereas a Venera observation of microseisms suggests ground motion more similar to a more active terrestrial location. Recurrence rate plots from in-situ measurements provide a context for seismic instrumentation on future planetary missions, e.g. to guide formulation of data compression schemes. While even small geophones can discriminate terrestrial activity rates, observations with guidance accelerometers are typically too insensitive to provide meaningful constraints (i.e. a non-zero number of “events”) on actual ground motion observations unless operated for very long periods.
We analyze the use of a promising technique for designing the flight trajectories to Venus with the application of a gravity-assist maneuver and resonant orbits to deliver a lander to regions on the ...surface of Venus with a high scientific significance where no landing can be made in the classical approach to designing the flight trajectories used in the missions of the Soviet Venera and Vega programs. Within the promising Russian Venera-D mission we consider the landing with the application of the above technique in Vellamo-South and Kutue-South, in which no landing is possible for the launch in 2031 and the classical approach to choosing a landing site. We take into account the constraints imposed by the requirements of accomplishing the flight mission to Venus by a spacecraft consisting of a lander and an orbital module. We show the efficiency of the applied technique both in choosing landing sites for the lander and in choosing an orbit for the orbital module.
•Venera 13 is consistent with a terrestrial silica-undersaturated basalt.•Venera 13 analysis suggests deep partial melting of a carbonated source region.•Venera 14 and Vega 2 are consistent with ...terrestrial tholeiites.•Igneous rocks on Venus maybe as compositionally diverse as those found on Earth.•Terrestrial analogs can constrain the type of data needed from future missions.
Igneous diversity is common on terrestrial planets and has been experimentally investigated for the Earth and Mars, but only suggested for Venus. Since Venus and Earth are sister planets and have similar bulk chemistry, experiments on terrestrial basalts can place constraints on the formation of the Venera and Vega basalts. Furthermore, experimental results can suggest the types of magmas that should be present on Venus if processes of differentiation similar to those taking place within the Earth are occurring on Venus, as suggested by the Venera and Vega analyses. The interpretation of the Venera 13 analysis as an alkali basalt suggests deep partial melting of a carbonated source region; while the identification of Venera 14 and Vega 2 as tholeiites suggest relatively shallow melting of a hydrous lherzolitic or peridotite source region. The residual liquids produced by differentiation of a Venus tholeiite, based on experiments on analog compositions, range from rhyolites to phonolites, depending on pressure of crystallization and bulk water content. Results from these crystallization experiments on tholeiitic terrestrial compositions can constrain the type and quality of data needed from future missions to determine the petrologic history of surface igneous rocks.
Venus was the first of the planets of the Solar System in the atmosphere of which electrical phenomena similar to lightning in the Earth’s atmosphere were discovered. Electrical discharges (lightning ...in the atmosphere of Venus) were discovered in 1978 in the
Venera-12
,
-11
, and
Pioneer Venus
missions, based on their electromagnetic radiation. The paradox, however, was that the search for optical flares remained unsuccessful for the past 40 years. In 2015, the
Akatsuki
spacecraft of the Japan Aerospace Exploration Agency was launched into orbit Venus satellite. It was designed to search for lightning and other studies of the meteorology of Venus by recording radiation in selected spectral ranges. In 2016, the
Akatsuki
orbiter successfully performed detailed observations of Venus in the near-infrared range in the “transparency windows” of the planet’s atmosphere, as well as in the ultraviolet and other ranges. The article presents the results of an alternative search for and successful detection of lightning flashes according to the
Akatsuki
project, but not in the ultraviolet or visible ranges, but in the near-IR range. A comparison of the results of calculations based on models of terrestrial lightning with the results of measurements made by the IR2 camera of the
Akatsuki
mission on Venus at a wavelength of 2.26 μm shows a close agreement between the experimental and calculated data.
The article covers the concept and historical aspects of development of automated space stations
Luna-16
,
Luna-17
, and
Venera-7
, which for the first time in the world successfully completed ...outstanding scientific programs. They opened the way for the world scientific community to study the Moon and the planets of the Solar System, providing invaluable experience for the development of the next-generation space missions.
Archaeoseismology can provide a useful chronological tool for constraining earthquakes and documenting significant evidence that would otherwise be lost. In this paper, we report a case of surface ...faulting on ancient man-made structures belonging to the archaeological site of Santa Venera al Pozzo situated along the eastern flank of Mt. Etna volcano in eastern Sicily (southern Italy), which is affected by well-developed tectonic faults. Geological surveys highlight a set of fractures affecting the archaeological ruins, suggesting the occurrence of a capable fault zone across the area. An integrated geophysical survey was carried out in order to identify the main subsurface tectonic discontinuity ascribable to the fault zone. The information derived from different geophysical techniques, such as electrical resistivity tomography, seismic refraction tomography, ground-penetrating radar, and magnetic surveys allowed us to infer that the fractures observed at the surface could have been produced by coseismic rupture. They are conceivably linked to a strong earthquake that probably occurred in the Roman period, around mid-end of the third-century AD; time constraints are inferred through the dating of buildings of the archaeological site.
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