Explore the vast range of titles available.

We report on observations made by the Mars Atmosphere and Volatile EvolutioN spacecraft at Mars, in the region of the ion plume. We observe that in some cases, when the number density of oxygen ions is comparable to the density of the solar wind protons interaction between both plasmas leads to formation in the magnetosheath of mini induced magnetospheres possessing all typical features of induced magnetospheres typically observed at Mars or Venus: a pileup of the magnetic field at the head of the ion cloud, magnetospheric cavity, partially void of solar wind protons, draping of the interplanetary magnetic field around the mini obstacle, formation of a magnetic tail with a current sheet, in which protons are accelerated by the magnetic field tensions. These new observations may shed a light on the mechanism of formation of induced magnetospheres. Plain Language Summary There is a class of the induced planetary magnetospheres when the absence of intrinsic magnetic field allows a direct interaction of solar wind with planetary atmospheres/ionospheres. We have shown the existence of mini‐induced magnetospheres at Mars. When the density of the extracted from the ionosphere oxygen ions becomes comparable with the proton density in solar wind mini‐induced magnetospheres with all typical features of the planetary induced magnetospheres arise. Key Points Oxygen ions extracted from the Martian ionosphere interact with shocked solar wind in the magnetosheath When the ion densities of both plasmas become comparable the mini induced magnetospheres are built These Magnetospheres possess all typical features of the classical induced magnetospheres

We report on observations made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, in the shocked solar wind‐ionosphere interface of Mars. We observe a strong asymmetry in plasma flow governed by the direction of the motional electric field. In the hemisphere, in which the motional electric field ∼−V × B is pointed outward the planet the solar wind flow is decelerated by the j × B force related to the magnetic field compression in the barrier. In contrast, in the opposite hemisphere, the solar wind flow is accelerated. The gain in velocity is about 100–200 km/s. The dynamics of ionospheric ions are also very different on both sides. Such an asymmetry implies very different patterns of the electric current closure and the electromagnetic forces in both hemispheres. Plain Language Summary Solar wind interacts directly with the ionosphere of Mars. The flow pattern in the interface region of such an interaction turns out to be different for different orientations of the interplanetary magnetic field. This asymmetry is governed by the direction of the motional electric field −1/c(V × B) aroused due to the solar wind flow across the magnetic field. Structure of the interface occurs very different. In the hemisphere, in which the motional electric field is pointed outward of Mars, the shocked solar wind flow is decelerated. In the hemisphere, in which the motional electric field is pointed toward the planet, the plasma flow is accelerated. Key Points Plasma flow in the solar wind‐ionosphere interface at Mars depends on sign of the cross‐flow component of the interplanetary magnetic field The motional electric field in the solar wind controls such a flow in the interface The shocked solar wind is accelerated in the interface of the hemisphere in which the motional electric field pointed toward the planet

The precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov–Gerasimenko are calculated, on the basis of its gravity field, showing it to be dusty, homogeneous, low-density and highly porous. An 'icy dirtball' cometary nucleus We are familiar with the bright coma and characteristic dust and plasma tails of comets when observed from ground, but the nucleus itself is hidden inside the coma. Comet nuclei consist of dust and mostly water ice, but their internal structure is essentially unknown. This paper reports results from the Radio Science Investigation (RSI) experiment on the Rosetta spacecraft that provide the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov–Gerasimenko based on its gravity field. Results point to a low-density, highly porous nucleus containing four times more dust than ice by mass and two times more dust than ice by volume. The authors conclude that the interior of the nucleus is homogeneous and constant in density on a global scale, with no large voids. Cometary nuclei consist mostly of dust and water ice 1 . Previous observations have found nuclei to be low-density and highly porous bodies 2 , 3 , 4 , but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov–Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kilometres. The gravitational point mass is GM  = 666.2 ± 0.2 cubic metres per second squared, giving a mass M  = (9,982 ± 3) × 10 9 kilograms. Together with the current estimate of the volume of the nucleus 5 , the average bulk density of the nucleus is 533 ± 6 kilograms per cubic metre. The nucleus appears to be a low-density, highly porous (72–74 per cent) dusty body, similar to that of comet 9P/Tempel 1 2 , 3 . The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

We present aeronomical observations collected using remote sensing instruments on board Venus Express, complemented with ground-based observations and numerical modeling. They are mostly based on VIRTIS and SPICAV measurements of airglow obtained in the nadir mode and at the limb above 90 km. They complement our understanding of the behavior of Venus’ upper atmosphere that was largely based on Pioneer Venus observations mostly performed over thirty years earlier. Following a summary of recent spectral data from the EUV to the infrared, we examine how these observations have improved our knowledge of the composition, thermal structure, dynamics and transport of the Venus upper atmosphere. We then synthesize progress in three-dimensional modeling of the upper atmosphere which is largely based on global mapping and observations of time variations of the nitric oxide and O 2 nightglow emissions. Processes controlling the escape flux of atoms to space are described. Results based on the VeRA radio propagation experiment are summarized and compared to ionospheric measurements collected during earlier space missions. Finally, we point out some unsolved and open questions generated by these recent datasets and model comparisons.

It is commonly believed that because of the direct solar wind interaction with the Martian atmosphere/ionosphere, the planet could have lost a significant part of its atmosphere. Closed field lines of the crustal magnetic field can weaken a transport of the ionospheric ions to the tail. Reconnection of the interplanetary magnetic field lines draping around Mars and the crustal magnetic field can also lead to a presense of sunward fluxes of planetary ions that might affect the total ion loss. The LatHyS (LATMOS Hybrid Simulation) three‐dimensional multispecies hybrid model is used here to characterize sunward fluxes of O+ ions and the magnetic field topology at Mars. It is shown that although reconnection between the interplanetary magnetic field (IMF) and the crustal magnetic fields strongly modifies the field topology, then sunward ion fluxes are rather small and do not significantly change the total ion loss. Plain Language Summary Although Mars has no a global intrinsic magnetic field and solar wind interacts directly with the planetary atmosphere/ionosphere, the existence of strong but localized crustal magnetic field modifies the field topology around Mars. As a result, the Martian magnetosphere contains elements of the intrinsic and the induced magnetospheres. Reconnection between the interplanetary magnetic field and the crustal magnetic field can generate the plasma flows toward the planet and decrease the ionospheric losses, which is very important for the evolution of the Mars atmosphere/ionosphere. We have performed the numerical simulations of these potential effects and shown that the sunward ion fluxes are significantly less than the losses induced by the solar wind impact on the Martian ionosphere. Key Points Hybrid simulations show a drastic change of the field topology at altitudes less than ∼1,000 km due to crustal field sources Although the magnetic field topology is modified, the sunward fluxes do not essentially affect the total ion loss Sunward fluxes of oxygen ions in the tail vary between ∼5% and ∼20% compared to the anti‐sunward fluxes

The vertical structure of the nightside ionosphere of Mars and its dependence on solar zenith angle are currently poorly determined, as is the importance of two key sources of nightside plasma, electron precipitation and transport of dayside plasma. We examined 37 electron density profiles of the ionosphere of Mars at solar zenith angles of 101°–123° obtained by the Mars Express Radio Science Experiment (MaRS) between 18 August and 1 October 2005. In general, solar activity was low during this period, although several solar energetic particle events did occur. The results show that (1) trends in peak electron density and altitude with solar zenith angle are consistent with transport of dayside plasma as an important plasma source up to 115°, but not higher; (2) peak altitudes of around 150 km observed at larger (>115°) solar zenith angles are consistent with simulated plasma production by electron precipitation; and (3) peak altitudes observed during solar energetic particle events are at 90 km, consistent with accepted models. Solar energetic particle events can be the main source of nightside plasma. These results challenge current models of the nightside ionosphere, including their implications for plasma sources. The total electron content is correlated with peak electron density, requiring explanation. Due to the geographical distribution of this data set (latitudes poleward of 38°N), we do not explore the influence of crustal field strength and direction on the nightside ionosphere. Key Points We examine 37 profiles of electron density in nightside Mars ionosphere Peak densities affected by solar zenith angle to 115 degrees Total electron content highly correlated with peak electron density

Asteroid 21 Lutetia was approached by the Rosetta spacecraft on 10 July 2010. The additional Doppler shift of the spacecraft radio signals imposed by 21 Lutetia's gravitational perturbation on the flyby trajectory were used to determine the mass of the asteroid. Calibrating and correcting for all Doppler contributions not associated with Lutetia, a least-squares fit to the residual frequency observations from 4 hours before to 6 hours after closest approach yields a mass of (1.700 ± 0.017) × 10¹ɸ kilograms. Using the volume model of Lutetia determined by the Rosetta Optical, Spectroscopie, and Infrared Remote Imaging System (OSIRIS) camera, the bulk density, an important parameter for clues to its composition and interior, is (3.4 ± 0.3) × 10³ kilograms per cubic meter.

Still delivering ESA's Venus Express probe has been in orbit since April 2006. Eight research papers in this issue present new results from the mission, covering the atmosphere, polar features, interactions with the solar wind and the controversial matter of venusian lightning. Håkan Svedham et al . open the section with a review of the similarities and (mostly) differences between Venus and its 'twin', the Earth. Andrew Ingersoll considers the latest results, and also how the project teams plan to make the most of the probe's remaining six years of life. Radio-sounding results from the first Venus Express Radio Science (VeRa) occultation season are reported, which determine the fine structure in temperatures at upper cloud-deck altitudes, detect a distinct day–night temperature difference in the southern middle atmosphere, and track day-to-day changes in Venus' ionosphere. The atmosphere and ionosphere of Venus have been studied in the past by spacecraft with remote sensing 1 , 2 , 3 , 4 or in situ techniques 3 , 4 . These early missions, however, have left us with questions about, for example, the atmospheric structure in the transition region from the upper troposphere to the lower mesosphere (50–90 km) and the remarkably variable structure of the ionosphere. Observations become increasingly difficult within and below the global cloud deck (<50 km altitude), where strong absorption greatly limits the available investigative spectrum to a few infrared windows and the radio range. Here we report radio-sounding results from the first Venus Express Radio Science 5 (VeRa) occultation season. We determine the fine structure in temperatures at upper cloud-deck altitudes, detect a distinct day–night temperature difference in the southern middle atmosphere, and track day-to-day changes in Venus’ ionosphere.

Deep eutectic solvents (DESs) have gained increased attention as alternative reaction media for biocatalysis in recent years. There are many investigations on biotransformations in a variety of DESs, but the purification of bioproducts from DES reaction mixtures has not yet been sufficiently addressed. The present study demonstrates a product recovery strategy from a DES reaction medium composed of (−)-menthol and dodecanoic acid. Since the DES is not formed by equimolar amounts of the substrates, but the eutectic point occurs at a 3:1 molar ratio, product isolation is an important task for effective biocatalytic process development, even if the limiting substrate is converted completely. Both DES compounds acted as substrates and reaction solvent in the lipase-catalyzed esterification to synthesize (−)-menthyl dodecanoate. The product (−)-menthyl dodecanoate ester was separated from the DES reaction mixture by a vacuum distillation step and a second esterification reaction can be performed with the recovered (−)-menthol.

We report independent results from two subgroups of the Mars Express Radio Science (MaRS) team who independently analyzed Mars Express (MEX) radio tracking data for the purpose of determining consistently the gravitational attraction of the moon Phobos on the MEX spacecraft, and hence the mass of Phobos. New values for the gravitational parameter (GM = 0.7127 ± 0.0021 × 10−3 km3/s2) and density of Phobos (1876 ± 20 kg/m3) provide meaningful new constraints on the corresponding range of the body's porosity (30% ± 5%), provide a basis for improved interpretation of the internal structure. We conclude that the interior of Phobos likely contains large voids. When applied to various hypotheses bearing on the origin of Phobos, these results are inconsistent with the proposition that Phobos is a captured asteroid.