What is the Oxygen Isotope Composition of Venus? The Scientific Case for Sample Return from Earth’s “Sister” Planet

Venus is Earth’s closest planetary neighbour and both bodies are of similar size and mass. As a consequence, Venus is often described as Earth’s sister planet. But the two worlds have followed very different evolutionary paths, with Earth having benign surface conditions, whereas Venus has a surface temperature of 464 °C and a surface pressure of 92 bar. These inhospitable surface conditions may partially explain why there has been such a dearth of space missions to Venus in recent years.The oxygen isotope composition of Venus is currently unknown. However, this single measurement (Δ17O) would have first order implications for our understanding of how large terrestrial planets are built. Recent isotopic studies indicate that the Solar System is bimodal in composition, divided into a carbonaceous chondrite (CC) group and a non-carbonaceous (NC) group. The CC group probably originated in the outer Solar System and the NC group in the inner Solar System. Venus comprises 41% by mass of the inner Solar System compared to 50% for Earth and only 5% for Mars. Models for building large terrestrial planets, such as Earth and Venus, would be significantly improved by a determination of the Δ17O composition of a returned sample from Venus. This measurement would help constrain the extent of early inner Solar System isotopic homogenisation and help to identify whether the feeding zones of the terrestrial planets were narrow or wide.Determining the Δ17O composition of Venus would also have significant implications for our understanding of how the Moon formed. Recent lunar formation models invoke a high energy impact between the proto-Earth and an inner Solar System-derived impactor body, Theia. The close isotopic similarity between the Earth and Moon is explained by these models as being a consequence of high-temperature, post-impact mixing. However, if Earth and Venus proved to be isotopic clones with respect to Δ17O, this would favour the classic, lower energy, giant impact scenario.We review the surface geology of Venus with the aim of identifying potential terrains that could be targeted by a robotic sample return mission. While the potentially ancient tessera terrains would be of great scientific interest, the need to minimise the influence of venusian weathering favours the sampling of young basaltic plains. In terms of a nominal sample mass, 10 g would be sufficient to undertake a full range of geochemical, isotopic and dating studies. However, it is important that additional material is collected as a legacy sample. As a consequence, a returned sample mass of at least 100 g should be recovered.Two scenarios for robotic sample return missions from Venus are presented, based on previous mission proposals. The most cost effective approach involves a “Grab and Go” strategy, either using a lander and separate orbiter, or possibly just a stand-alone lander. Sample return could also be achieved as part of a more ambitious, extended mission to study the venusian atmosphere. In both scenarios it is critical to obtain a surface atmospheric sample to define the extent of atmosphere-lithosphere oxygen isotopic disequilibrium. Surface sampling would be carried out by multiple techniques (drill, scoop, “vacuum-cleaner” device) to ensure success. Surface operations would take no longer than one hour.Analysis of returned samples would provide a firm basis for assessing similarities and differences between the evolution of Venus, Earth, Mars and smaller bodies such as Vesta. The Solar System provides an important case study in how two almost identical bodies, Earth and Venus, could have had such a divergent evolution. Finally, Venus, with its runaway greenhouse atmosphere, may provide data relevant to the understanding of similar less extreme processes on Earth. Venus is Earth’s planetary twin and deserves to be better studied and understood. In a wider context, analysis of returned samples from Venus would provide data relevant to the study of exoplanetary systems

Observation of a sudden cessation of a very-high-energy gamma-ray flare in PKS 1510-089 with H.E.S.S. and MAGIC in May 2016

The flat spectrum radio quasar (FSRQ) PKS 1510-089 is known for its complex multiwavelength behavior, and is one of only a few FSRQs detected at very high energy (VHE, E >100 GeV) -rays. VHE -ray observations with H.E.S.S. and MAGIC during late May and early June 2016 resulted in the detection of an unprecedented flare, which reveals for the first time VHE -ray intranight variability in this source. While a common variability timescale of 1.5 hr is found, there is a significant deviation near the end of the flare with a timescale of ∼ 20 min marking the cessation of the event. The peak flux is nearly two orders of magnitude above the low-level emission. For the first time, curvature is detected in the VHE -ray spectrum of PKS 1510-089, which is fully explained through absorption by the extragalactic background light. Optical R-band observations with ATOM reveal a counterpart of the -ray flare, even though the detailed flux evolution differs from the VHE lightcurve. Interestingly, a steep flux decrease is observed at the same time as the cessation of the VHE flare. In the high energy (HE, E >100 MeV) -ray band only a moderate flux increase is observed with Fermi-LAT, while the HE -ray spectrum significantly hardens up to a photon index of 1.6. A search for broad-line region (BLR) absorption features in the -ray spectrum indicates that the emission region is located outside of the BLR. Radio VLBI observations reveal a fast moving knot interacting with a standing jet feature around the time of the flare. As the standing feature is located ∼ 50 pc from the black hole, the emission region of the flare may have been located at a significant distance from the black hole. If this correlation is indeed true, VHE rays have been produced far down the jet where turbulent plasma crosses a standing shock.Accepted manuscrip

Órgãos internos e trato digestório de novilhos superprecoces não castrados ou castrados, de dois grupos genéticos

Avaliaram-se as características dos órgãos e do trato gastrintestinal de novilhos com duas condições sexuais - castrados e não castrados -, com predomínio genético Charolês ou Nelore com idade e peso médios iniciais de 12 meses e 267kg, respectivamente. Os novilhos foram confinados até o peso de abate médio preestabelecido de 400kg. A dieta alimentar continha relação volumoso:concentrado de 50:50 (base na matéria seca), com 10% de proteína bruta. O delineamento experimental utilizado foi o inteiramente ao acaso, em arranjo fatorial de 2x2 (duas condições sexuais x dois predomínios genéticos). Para o peso absoluto do omaso, observou-se interação significativa de genótipo versus condição sexual dos novilhos. Animais não castrados apresentaram maiores pesos absolutos dos rins (0,81 versus 0,66kg), do abomaso (1,20 versus 1,00kg) e dos intestinos, nas diferentes formas de expressão, em comparação aos castrados. Os animais com predomínio Charolês apresentaram maiores pesos absolutos do omaso (4,24 versus 3,46kg), dos intestinos (8,18 versus 6,84kg) e do total do trato digestório (16,88 versus 14,90kg) em relação aos animais com predominância Nelore. Não houve correlação entre o rendimento de carcaça e os componentes não integrantes da carcaça

Composição corporal de garrotes inteiros de três grupos genéticos nas fases de recria e terminação Body composition of young bulls of three genetic groups in the growing and finishing phases

Com os objetivos de avaliar a composição corporal e identificar características corporais mensuráveis capazes de estimar o tamanho relativo de componentes corporais, foram utilizados 36 garrotes inteiros, sendo 12 Nelore, 12 ½ Holandês x ½ Zebu e 12 ½ Caracu x ½ Zebu. Em cada grupo genético, havia seis animais de cada fase de produção: recria e terminação, com peso inicial próximo a 225 kg e 330 kg, respectivamente. Os animais foram mantidos em regime de confinamento até o abate, realizado de acordo com o peso: 310 a 340 kg PV para os animais na fase de recria e 420 a 470 kg PV para aqueles na fase de terminação. Foi fornecida a mesma dieta a todos os animais, com 50% da matéria seca à base de concentrado e 50% de silagem pré-seca de coastcross. Utilizou-se um fator geral de 0,8693 para conversão do peso vivo em peso de corpo vazio (obtido a partir dos dados de todos os animais do experimento). Animais provenientes de seleção para corte na categoria terminação apresentaram maiores rendimentos de carcaça (59,2%) que aqueles de origem leiteira (56,33%). Grupos genéticos de raças com aptidão leiteira mostraram tamanhos relativos de órgãos 9% maior, 21% menos tecido adiposo na carcaça, bem como maior participação da gordura interna no total de tecido adiposo corporal. Em razão das baixas correlações encontradas, não parece confiável estimar os tamanhos relativos dos componentes corporais estudados a partir das características corporais mensuráveis analisadas.<br>To evaluate the body composition, and to identify measurable body characteristics capable to estimate the relative size of body components, 36 young bulls (12 Nellore, 12 ½ Holstein x ½ Zebu, and 12 ½ Caracu x ½ Cebu) were used. In each genetic group, six animals of each production phase were used: growing animals with initial weight of 225 kg and the finishing ones with initial weight of 330 kg. The animals were maintained in confinement regime to reach 310 to 340 kg of weight for the growing animals and 420 to 470 kg of weight for the finishing ones. The same diet was fed to all the animals, with concentrate level of 50% in the dry matter and 50% of coastcross hay. A general factor of .8693 was adopted to conversion of live weight in empty body weight (obtained with the records of all the animals in the experiment). Animals from a beef selection origin, in finishing group, presented higher dressing percentage (59.2%) that those of milk selection origin (56.33%). Genetic groups originating from breeds with milk aptitude showed higher relative sizes of organs (9% more), 21% smaller total fatty tissue in carcass, as well as higher participation of internal fatty tissue in total fatty tissue. Despite of the low correlations, it is not reliable to estimate the relative sizes of the body components studied from the analyzed measurable body characteristics