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Early in the Moon's history volcanic outgassing may have produced a periodic millibar level atmosphere (Needham and Kring 2017). We examined the relevant atmospheric escape processes and lifetime of such an atmosphere. Thermal escape rates were calculated as a function of atmospheric mass for a range of temperatures including the effect of the presence of a light constituent such as H 2. Photochemical escape and atmospheric sputtering were calculated using estimates of the higher EUV and plasma fluxes consistent with the early Sun. The often used surface Jeans calculation carried out in Vondrak (1974) is not applicable for the scale and composition of the atmosphere considered. We show that solar driven non-thermal escape can remove an early CO millibar level atmosphere on the order of ~1 Myr if the average exobase temperature is below ~350–400 K. However, if solar UV/EUV absorption heats the upper atmosphere to temperatures > ~ 400 K thermal escape increasingly dominates the loss rate, and we estimated a minimum lifetime of 100's of years considering energy limited escape. • An early Moon CO atmosphere is lost by thermal and non-thermal escape on order of Myrs. • Lifetime of an early Moon atmosphere depends on efficiency of solar EUV heating. • Thermal escape dominates non-thermal escape for atmosphere temperatures >400 K. [ABSTRACT FROM AUTHOR]

The article offers information on the findings on tenuous lunar surface from the data of Chandra's Altitudinal Composition Explorer (CHACE) through the Moon Impact Probe (MIP) of Chandrayaan-1, the India's first lunar probe to the moon. Topics discussed include analysis of mass spectra found from the Chandrayaan-1space craft, surface boundary exosphere (SBE) of moon, and the discovery of lunar water in mass spectra.

The article discusses the strange existence of a lunar atmosphere that reflects light from surfaces illuminated by direct sunlight. It notes that visual and astronomical observers has debated on the historic challenge hinted by Harold Hill. It adds that the crews of Apollo 10 have commented on the earthshine that resonates in the pseudo-twilight on the moon.

We examine the dynamics of energetic magnetospheric electrons exposed to the highly perturbed and asymmetric plasma environment of Jupiter's moon Callisto. The interaction of the (nearly) corotating magnetospheric plasma with Callisto's ionosphere and induced dipole locally generates intense electromagnetic pileup and draping signatures which vary as a function of the moon's distance to the center of Jupiter's magnetospheric current sheet. In our study, these field perturbations are represented using output from the AIKEF hybrid (kinetic ions, fluid electrons) model of Callisto's interaction with the corotating plasma. In order to constrain the influence of Callisto's variable electromagnetic environment on the dynamics of energetic electrons, we trace the trajectories of more than 6.7 million test particles as they travel through a distinct configuration of the locally perturbed fields. We present spatially resolved maps that display the accessibility of Callisto to electrons at energies E between 10 1 keV ≤ E ≤ 10 5 keV for multiple sets of these perturbed fields, corresponding to select distances of the moon to the center of the Jovian current sheet. The electromagnetic field perturbations near Callisto play a crucial role in generating inhomogeneous precipitation of energetic electrons onto the top of the moon's atmosphere. In particular, Callisto's Jupiter-facing and Jupiter-averted hemispheres are partially protected from energetic electron precipitation: when located far above or below the center of Jupiter's current sheet, Callisto's induced dipole shields the apices of these hemispheres, whereas near the center of the sheet, strong field line draping protects these regions. In contrast to this, the apex of Callisto's trailing hemisphere is exposed to intense energetic electron precipitation at any distance to the center of the Jovian current sheet. We also present maps of energetic electron accessibility during the Galileo C3, C9, and C10 flybys, and calculate the intensity of energetic electron flux onto multiple locations at the top of Callisto's atmosphere. These non-uniform electron fluxes likely cause inhomogeneous ionization of Callisto's atmosphere and may even contribute to irregular erosion of the surface. This paper is a companion to Liuzzo et al. (2019), who studied the dynamics of energetic ions near Callisto. • Callisto's perturbed electromagnetic environment strongly affects energetic electron dynamics. • Induced fields and Alfvén wings partially shield Callisto from impinging magnetospheric electrons. • Energetic electron precipitation onto Callisto's atmosphere is highly inhomogeneous. • Electrons may leave Callisto's local environment, bounce, and then return, causing asymmetric precipitation patterns. [ABSTRACT FROM AUTHOR]

Nearby ‘open’ clusters of stars (those that are not gravitationally bound) have played a crucial role in the development of stellar astronomy because, as a consequence of the stars having a common age, they provide excellent natural laboratories to test theoretical stellar models. Clusters also play a fundamental part in determining distance scales. The satellite Hipparcos surprisingly found that an extensively studied open cluster-the Pleiades (also known as the Seven Sisters)-had a distance of D = 118 ± 4?pc (refs 2, 3), about ten per cent smaller than the accepted value. The discrepancy generated a spirited debate because the implication was that either current stellar models were incorrect by a surprising amount or Hipparcos was giving incorrect distances. Here we report the orbital parameters of the bright double star Atlas in the Pleiades, using long-baseline optical/infrared interferometry. From the data we derive a firm lower bound of D > 127?pc, with the most likely range being 133 < D < 137?pc. Our result reaffirms the fidelity of current stellar models. [ABSTRACT FROM AUTHOR]

Presents a study of the mechanisms used to resupply the atmospheres of Mercury and the Moon with atomic sodium and potassium. The flux at the lunar surface of ultraviolet photons from the sun; Solar heating of the surface showing thermal desorption on Mercury; Measurements; Procedure; Interpretations of tables; Calculations; Conclusions.

This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or a moon and its atmosphere and surface (including hydrosphere and biosphere) can affect habitability of the celestial body. It does not consider in detail the role of the central star but focusses more on surface conditions capable of sustaining life. We deal with fundamental issues of planetary habitability, i.e. the environmental conditions capable of sustaining life, and the above-mentioned interactions can affect the habitability of the celestial body. We address some hotly debated questions including: How do core and mantle affect the evolution and habitability of planets? What are the consequences of mantle overturn on the evolution of the interior and atmosphere? What is the role of the global carbon and water cycles? What influence do comet and asteroid impacts exert on the evolution of the planet? How does life interact with the evolution of the Earth's geosphere and atmosphere? How can knowledge of the solar system geophysics and habitability be applied to exoplanets? In addition, we address the identification of preserved life tracers in the context of the interaction of life with planetary evolution. [ABSTRACT FROM AUTHOR]

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can enhance the science return of planetary missions. By shadow tracking the spacecraft signal using radio telescopes from VLBI networks, the PRIDE technique provides precise open-loop Doppler and near-field VLBI observables (Duev et al. 2012, Bocanegra-Bahamon et al. 2018a) to find the radial velocity of the spacecraft and its position in the plane of the sky. This information is not only important for navigation, but it can also be used for many science applications. One such case is the study of planetary atmospheres by means of radio occultation experiments. The application of PRIDE for atmospheric studies has been demonstrated by observing ESA's Venus Express (VEX) and Mars Express (MEX) during multiple Venus and Mars occultation events(Bocanegra-Bahamon et al. 2018b). From these observations density, temperature and pressure profiles of Venus and Mars were derived to characterize the planets' ionosphere and neutral atmosphere. The noise budget of the observations indicated that the quality of the detections are comparable to those of NASA's and ESA's deep space networks (Bocanegra-Bahamon et al. 2018a). With PRIDE, making use of open-loop Doppler data, EVN stations were able to sound deeper layers of Venus' thick atmosphere when compared to closed-loop Doppler data provided by ESA's New Norcia. With the wideband spectral analysis of PRIDE, we showed that even with small antennas, such as the 12-m AuScope's Katherine, the spacecraft signal can be detected below Venus' cloud layer.Radio occultation experiments with PRIDE can exploit the advantage of having access to large radio telescopes from different VLBI networks. Additionally, due to the wide coverage of the networks, the setup can be optimized to ensure high SNR signal detections. This offers a great opportunity when conducting radio occultation experiments with limited SNR of planets/moons with thick atmospheres. Such is the case of experiments in the Jovian system, for which the PRIDE team is preparing as one of the experiments selected by ESA for the JUpiter ICy moons Explorer mission (JUICE) mission.Duev, D.A., Molera Calves, G., and Pogrebenko, S.V., Gurvits, L.I., Cimo, G. and Bocanegra Bahamon, T.M.:Spacecraft VLBI and Doppler tracking: algorithms and implementation, Astronomy & Astrophysics, Vol. 541, 2012.Bocanegra-Bahamon, T.M., Molera Calves,G. and Gurvits, L.I., Duev, D.A., Pogrebenko, S.V., Cimo, G. and Dirkx, D. and Rosenblatt, P.: Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos Flyby-II. Doppler tracking: Formulation of observed and computed values, and noise budget, Astronomy & Astrophysics, 609, A59, 2018a.Bocanegra-Bahamon, T.M., Molera Calves,G. and Gurvits, L.I., Dirkx, D. et al.: Venus Expess radio occultation observed by PRIDE, accepted in Astronomy & Astrophysics, 2018b.Tellmann, S. Paetzold M., et al.:Structure of the Venus neutral atmosphere as observed by the Radio Science experiment VeRa on Venus Expres. Journal of Geophysical Research: Planets,114,E9,2009. [ABSTRACT FROM AUTHOR]

Discoveries stemming from the Apollo 11 mission solved many problems that had vexed scientists for hundreds of years. Research and discoveries over the preceding 360 years identified many critical questions and led to a variety of answers: How did the Moon form, how old is its surface, what is the origin of lunar craters, does the Moon have an atmosphere, how did the Moon change over time, is the Moon geologically active today, and did life play any role in lunar evolution? In general, scientists could not convincingly answer most of these questions because they had too little data and too little understanding of astronomy and geology, and were forced to rely on reasoning and speculation, in some cases wasting hundreds of years of effort. Surprisingly, by 1969, most of the questions had been correctly answered, but a paucity of data made it uncertain which answers were correct. [ABSTRACT FROM AUTHOR]

The article reports on the association of the phases of the moon with the global rainfall. Topics discussed include an outline on the discovery of pressure response to atmospheric tide, the detection of global tropical precipitation pattern, the relation between increased pressure and increased temperature, and the effect of lunar tides on the atmosphere.

The article offers information on in situ measurement which show details of the production and evolution of the lunar exosphere. It mentions the Ultraviolet and Visible Spectrometer (UVS) measurements which offer a step towards knowing the composition of the lunar atmosphere and the processes that control the variability and distribution of its components. The connection of the variation of the sodium and potassium on the rotation of the moon is cited.

From the observations of the gravitational field and the figure of the Moon, it is known that its center of mass (briefly COM) does not coincide with the center of figure (COF), and the line “COF/COM” is not directed to the center of the Earth, but deviates from it to the South-East. Here we study the deviation of the lunar COM to the East from the mean direction to Earth.At first, we consider the optical libration of a satellite with synchronous rotation around the planet for an observer at a point on second (empty) orbit focus. It is found that the main axis of inertia of the satellite has asymmetric nonlinear oscillations with amplitude proportional to the square of the orbit eccentricity. Given this effect, a mechanism of tidal secular evolution of the Moon’s orbit is offered that explains up to 20% of the known displacement of the lunar COM to the East. It is concluded that from the alternative—evolution of the Moon’s orbit with a decrease or increase in eccentricity—only the scenario of evolution with a monotonous increase in orbit eccentricity agrees with the displacement of lunar COM to the East. The precise calculations available confirm that now the eccentricity of the lunar orbit is actually increasing and therefore in the past it was less than its modern value, e=0.0549.To fully explain the displacement of the Moon’s COM to the East was deduced a second mechanism, which is based on the reliable effect of tidal changes in the shape of the Moon. For this purpose the differential equation which governs the process of displacement of the Moon’s COM to the East with inevitable rounding off its form in the tidal increase process of the distance between the Earth and the Moon is derived. The second mechanism not only explains the Moon’s COM displacement to the East, but it also predicts that the elongation of the lunar figure in the early epoch was significant and could reach the value ε≈0.31. Applying the theory of tidal equilibrium figures, we can estimate how close to the Earth the Moon could have formed. [ABSTRACT FROM AUTHOR]