Insights Into Chemical Reactions at the Beginning of the Universe: From HeH+ to H3+

At the dawn of the Universe, the ions of the light elements produced in the Big Bang nucleosynthesis recombined with each other. In our present study, we have tried to mimic the conditions in the early Universe to show how the recombination process would have led to the formation of the first ever formed diatomic species of the Universe: HeH+, as well as the subsequent processes that would have led to the formation of the simplest triatomic species: H3+. We have also studied some special cases: higher positive charge with fewer number of hydrogen atoms in a dense atmosphere, and the formation of unusual and interesting linear, dicationic He chains beginning from light elements He and H in a positively charged atmosphere. For all the simulations, the ab initio nanoreactor (AINR) dynamics method has been employed.

Titan's Interior Structure and Dynamics After the Cassini-Huygens Mission

The Cassini-Huygens mission that explored the Saturn system during the period 2004–2017 revolutionized our understanding of Titan, the only known moon with a dense atmosphere and the only body, besides Earth, with stable surface liquids. Its predominantly nitrogen atmosphere also contains a few percent of methane that is photolyzed on short geological timescales to form ethane and more complex organic molecules. The presence of a significant amount of methane and 40Ar, the decay product of 40K, argues for exchange processes from the interior to the surface. Here we review the information that constrains Titan's interior structure. Gravity and orbital data suggest that Titan is an ocean world, which implies differentiation into a hydrosphere and a rocky core. The mass and gravity data complemented by equations of state constrain the ocean density and composition as well as the hydrosphere thickness. We present end-member models, review the dynamics of each layer, and discuss the global evolution consistent with the Cassini-Huygens data. ▪ Titan is the only moon with a dense atmosphere where organic molecules are synthesized and have sedimented at the surface. ▪ The Cassini-Huygens mission demonstrated that Titan is an ocean world with an internal water shell and liquid hydrocarbon seas at the poles. ▪ Interactions between water, rock, and organics may have occurred during most of Titan's evolution, which has strong astrobiological implications. ▪ Data collected by the Dragonfly mission and comparison with the JUpiter ICy moons Explorer (JUICE) data for Ganymede will further reveal Titan's astrobiology potential. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 49 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The vaporization behavior of carbon and hydrogen from the early global magma ocean

<p>Estimating the fluxes and speciation of volatiles during the existence of a global magma ocean is fundamental for understanding the cooling history of the early Earth and for quantifying the volatile budget of the present day. Using first-principles molecular dynamics, we predict the vaporization rate of carbon and hydrogen at the interface between the magma ocean and the hot dense atmosphere, just after the Moon-forming impact. The concentration of carbon and the oxidation state of the melts affect the speciation of the vaporized carbon molecules (e.g., the ratio of carbon dioxide to carbon monoxide), but do not appear to affect the overall volatility of carbon. We find that carbon is rapidly devolatilized even under pressure, while hydrogen remains mostly dissolved in the melt during the devolatilization process of carbon. Thus, in the early stages of the global magma ocean, significantly more carbon than hydrogen would have been released into the atmosphere, and it is only after the atmospheric pressure decreased, that much of the hydrogen devolatilized from the melt. At temperatures of 5000 K (and above), we predict that bubbles in the magma ocean contained a significant fraction of silicate vapor, increasing with decreasing depths with the growth of the bubbles, affecting the transport and rheological properties of the magma ocean. As the temperature cooled, the silicate species condensed back into the magma ocean, leaving highly volatile atmophile species, such as CO<sub>2</sub> and H<sub>2</sub>O, as the dominant species in the atmosphere. Due to the greenhouse nature of CO<sub>2</sub>, its concentration in the atmosphere would have had a considerable effect on the cooling rate of the early Earth.</p>

On the thermal atmosphere evaporation of hot neptune GJ 436b

В данной работе с помощью одномерной самосогласованной аэрономической модели были получены высотные профили температуры, скорости и плотности для горячего нептуна GJ 436b. Мы проследили расширение газовой оболочки под действием нагрева от жесткого излучения родительской звезды от тонкого атмосферного слоя 1.02R 0 до 5R 0 . Используемая модель учитывает вклад надтепловых частиц, что значительно уточняет функцию нагрева атмосферы. Установлено, что формируется структура атмосферы с двумя характерными шкалами высоты, отвечающими относительно плотной атмосфере и более разреженной короне. Также был посчитан темп оттока атмосферы, составивший около 1.6 × 10 9 г с -1 , что ниже результатов, полученных авторами других расчетов. In this work the height profiles of temperature, velocity, and density were obtained for the hot neptune GJ 436b, using a one-dimensional self-consistent aeronomic model. We traced the expansion of the gas envelope affected by heating from the extreme radiation of the host star from the thin atmospheric layer 1.02R 0 up to 5R 0 . The model used takes into account the contribution of suprathermal particles, which significantly refines the atmospheric heating function. It was found that the structure of the atmosphere is being formed with two characteristic altitude scales corresponding to a relatively dense atmosphere and a more rarefied corona. The atmospheric mass loss rate was also calculated, it was found to be about 1.6 × 10 9 g s -1 , which is lower than the results obtained by the authors of other calculations.

Estimating the lifetime and Reentry of the Aluminum Space Debris of Sizes (1 and 10 cm) in LEO under Atmosphere Drag Effects

This study attempts to address the lifetime and reentry of the space debris in low earth orbit LEO which extends from 200 to 1200 km. In this study a new Computer programs were designed to simulate the orbit dynamics of space debris lifetime and reentry under atmospheric drag force using Runge-Kutta Method to solve the differential equations of drag force. This model was adapted with the Drag Thermosphere Model (DTM78, 94), the Aluminum 2024 space debris in certain size (1&10 cm) were used in this study, which is frequently employed in the structure of spacecraft and aerospace designs. The selected atmospheric model for this investigation was the drag thermospheric models DTM78 and DTM94, because of this dependence on solar and geomagnetic activities. It was found that the lifetime of the space debris increases with increasing perigee altitudes. It was also found that the elliptical shape of the debris orbit would change gradually into a circular shape, then its kinetic energy would be transformed into heat and hence the debris might be destroyed in the dense atmosphere.

Investigation of the Ballistic Descent Mode for a Maneuverable Lander to the Venus Surface

At present, various projects to continue fundamental investigations of Venus are considered in Russia and abroad. It means that the issue of developing a landing module to reach the surface of the planet becomes topical, as the module might provide access to the regions most attractive in terms of research. We propose to use a landing module of the lifting body type, which, as compared to a ballistic class module, is not unacceptably complicated in terms of design and at the same time features a lift-to-drag ratio adequate for solving manoeuvring problems arising in the process of descent into the Venusian atmosphere to reach the target landing area. We consider potential descent trajectories available to a landing module of this type, including the possibility of performing a maximum lateral manoeuvre; we took into consideration its long-period trajectories characterised by multiple re-entries into the dense atmosphere and compared these trajectories to the descent trajectory of a conventional ballistic class landing module. We show that using a manoeuvrable craft expands the selection of potential landing regions, as well as reduces loads and broadens the scope of scientific problems to be solved and studies to be undertaken

A radiation belt of energetic protons located between Saturn and its rings

Saturn has a sufficiently strong dipole magnetic field to trap high-energy charged particles and form radiation belts, which have been observed outside its rings. Whether stable radiation belts exist near the planet and inward of the rings was previously unknown. The Cassini spacecraft’s Magnetosphere Imaging Instrument obtained measurements of a radiation belt that lies just above Saturn’s dense atmosphere and is decoupled from the rest of the magnetosphere by the planet’s A- to C-rings. The belt extends across the D-ring and comprises protons produced through cosmic ray albedo neutron decay and multiple charge-exchange reactions. These protons are lost to atmospheric neutrals and D-ring dust. Strong proton depletions that map onto features on the D-ring indicate a highly structured and diverse dust environment near Saturn.

ESTHER'S ETHER: ATMOSPHERIC CHARACTER IN CHARLES DICKENS'S BLEAK HOUSE

Five chapters after the famousfoggy opening of Charles Dickens'sBleak House(1853), the novel's protagonist Esther Summerson disappears into thick air. Esther's “darling,” the young orphan Ada Clare, first discloses her companion's climatic dissolution when she celebrates her kind-hearted treatment of the hapless Jellyby children. Although Ada and Esther's guardian John Jarndyce maintains that a shower of “sugar-plums, or three-cornered raspberry tarts,” might be a suitable remedy for the children's neglect, Ada contradicts this proposition when she makes the odd claim, “It did better than that. It rained Esther” (61). This assertion that Esther's precipitated personhood is a “better” palliative than an abundance of sugared confections undoubtedly evinces Ada's childlike appreciation of her companion's effusive goodness. Within the larger scope of the novel, however, the remarkable notion that Esther's seemingly embodied actions and emotions are equivalent to rain, raises an unexpected but essential question: To what ends does Dickens's protagonist evaporate into the dense atmosphere we traditionally associate with the setting ofBleak House?