A carbon nanotube based ion source for planetary space mass spectrometry.

Ion sources are used in mass and energy spectrometry to ionize the neutral particles entering the instrument. The most classical technique used in planetary exploration is hot filaments emitting electrons with few tens of eV and impacting the neutral particles. The main limitations of such emitters are power consumption and outgassing due to heating of their local environment. Here, we built, tested, and demonstrated the advantages of using carbon nanotubes to replace hot filaments. Such emitters are based on a cold approach, use a limited amount of power, and achieve essentially the same efficiency as the hot filament-based source of ionization.

Inner southern magnetosphere observation of Mercury via SERENA ion sensors in BepiColombo mission.

Mercury's southern inner magnetosphere is an unexplored region as it was not observed by earlier space missions. In October 2021, BepiColombo mission has passed through this region during its first Mercury flyby. Here, we describe the observations of SERENA ion sensors nearby and inside Mercury's magnetosphere. An intermittent high-energy signal, possibly due to an interplanetary magnetic flux rope, has been observed downstream Mercury, together with low energy solar wind. Low energy ions, possibly due to satellite outgassing, were detected outside the magnetosphere. The dayside magnetopause and bow-shock crossing were much closer to the planet than expected, signature of a highly eroded magnetosphere. Different ion populations have been observed inside the magnetosphere, like low latitude boundary layer at magnetopause inbound and partial ring current at dawn close to the planet. These observations are important for understanding the weak magnetosphere behavior so close to the Sun, revealing details never reached before.

Mars' plasma system. Scientific potential of coordinated multipoint missions: "The next generation".

The objective of this White Paper, submitted to ESA's Voyage 2050 call, is to get a more holistic knowledge of the dynamics of the Martian plasma system, from its surface up to the undisturbed solar wind outside of the induced magnetosphere. This can only be achieved with coordinated multi-point observations with high temporal resolution as they have the scientific potential to track the whole dynamics of the system (from small to large scales), and they constitute the next generation of the exploration of Mars analogous to what happened at Earth a few decades ago. This White Paper discusses the key science questions that are still open at Mars and how they could be addressed with coordinated multipoint missions. The main science questions are: (i) How does solar wind driving impact the dynamics of the magnetosphere and ionosphere? (ii) What is the structure and nature of the tail of Mars' magnetosphere at all scales? (iii) How does the lower atmosphere couple to the upper atmosphere? (iv) Why should we have a permanent in-situ Space Weather monitor at Mars? Each science question is devoted to a specific plasma region, and includes several specific scientific objectives to study in the coming decades. In addition, two mission concepts are also proposed based on coordinated multi-point science from a constellation of orbiting and ground-based platforms, which focus on understanding and solving the current science gaps.

Volatiles and Refractories in Surface-Bounded Exospheres in the Inner Solar System.

Volatiles and refractories represent the two end-members in the volatility range of species in any surface-bounded exosphere. Volatiles include elements that do not interact strongly with the surface, such as neon (detected on the Moon) and helium (detected both on the Moon and at Mercury), but also argon, a noble gas (detected on the Moon) that surprisingly adsorbs at the cold lunar nighttime surface. Refractories include species such as calcium, magnesium, iron, and aluminum, all of which have very strong bonds with the lunar surface and thus need energetic processes to be ejected into the exosphere. Here we focus on the properties of species that have been detected in the exospheres of inner Solar System bodies, specifically the Moon and Mercury, and how they provide important information to understand source and loss processes of these exospheres, as well as their dependence on variations in external drivers.

SERENA: Particle Instrument Suite for Determining the Sun-Mercury Interaction from BepiColombo.

The ESA-JAXA BepiColombo mission to Mercury will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric particle dynamics at Mercury as well as their interactions with solar wind, solar radiation, and interplanetary dust. The particle instrument suite SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) is flying in space on-board the BepiColombo Mercury Planetary Orbiter (MPO) and is the only instrument for ion and neutral particle detection aboard the MPO. It comprises four independent sensors: ELENA for neutral particle flow detection, Strofio for neutral gas detection, PICAM for planetary ions observations, and MIPA, mostly for solar wind ion measurements. SERENA is managed by a System Control Unit located inside the ELENA box. In the present paper the scientific goals of this suite are described, and then the four units are detailed, as well as their major features and calibration results. Finally, the SERENA operational activities are shown during the orbital path around Mercury, with also some reference to the activities planned during the long cruise phase.

Multi-scale simulation of electron emission from a triode-type electron source with a carbon-nanotube column array cathode.

We have designed and fabricated a new type of field electron source for a novel onboard mass spectrometer. The new electron source, which is a field effect emitter in a triode configuration, consists of a CNT-column array cathode and an extraction gate with holes that are aligned concentrically with respect to the cylindrical CNT columns. In triode mode operation, cathode currents as large as ~420 µA have been emitted with an anode-to-gate current ratio of ~1.5. To account for the observed emission characteristics of the new electron source, we have carried out multi-scale simulations that combine a three-dimensional (3D) microscopic model in the vicinity of an actual emission site with a two-dimensional (2D) macroscopic model that covers the whole device structure. Because the mesh size in the microscopic 3D model is as small as 100 nm, the contributions of the extruding CNT bundle at the top edge of an electron column can be examined in detail. Unlike the macroscopic 2D simulation that shows only small field enhancement at CNT column's top edge, the multi-scale simulation successfully reproduced the local electric field strongly enough to emit the measured cathode currents and the electric field distribution which is consistent with the measured anode-to-gate current ratio.

Adrenal inhibition following a single dose of etomidate in intubated traumatic brain injury victims.

BACKGROUND: Etomidate is frequently used to intubate traumatic brain injury (TBI) victims, even though it has been linked to adrenal insufficiency (AI) in some populations. Few studies have explored the risk of prolonged etomidate-induced AI among TBI victims. OBJECTIVE: To determine the risk and the length of AI induced by etomidate in patients intubated for moderate and severe TBI. METHODS: Participants in this observational study were moderate to severe intubated TBI victims aged ≥ 16 years. The anesthetic used (etomidate versus others) was determined solely by the treating emergency physician. Adrenocorticotropic hormone (ACTH) stimulation tests (250 µg) were performed 24, 48, and 168 hours after intubation. AI was defined as an increase in serum cortisol 1 hour post-ACTH test (delta cortisol) of less than 248.4 nmol/L. RESULTS: Forty subjects (participation 42.6%) underwent ACTH testing. Fifteen received etomidate, and 25 received another anesthetic. There were no statistically significant differences between groups as to the cumulative incidence of AI at any measurement time. However, at 24 hours, exploratory post hoc analyses showed a significant decrease in delta cortisol (adjusted means: etomidate group: 305.1 nmol/L, 95% CI 214.7-384.8 versus other anesthetics: 500.5 nmol/L, 95% CI 441.8-565.7). This decrease was not present at 48 and 168 hours. CONCLUSION: In TBI victims, although a single dose of etomidate does not increase the cumulative incidence of AI as defined, it seems to decrease the adrenal response to an ACTH test for 24 hours. The clinical impacts of this finding remain to be determined.

Geophysical and atmospheric evolution of habitable planets.

The evolution of Earth-like habitable planets is a complex process that depends on the geodynamical and geophysical environments. In particular, it is necessary that plate tectonics remain active over billions of years. These geophysically active environments are strongly coupled to a planet's host star parameters, such as mass, luminosity and activity, orbit location of the habitable zone, and the planet's initial water inventory. Depending on the host star's radiation and particle flux evolution, the composition in the thermosphere, and the availability of an active magnetic dynamo, the atmospheres of Earth-like planets within their habitable zones are differently affected due to thermal and nonthermal escape processes. For some planets, strong atmospheric escape could even effect the stability of the atmosphere.

Efficacy of a T-piece system and a continuous positive airway pressure system for apnea testing in the diagnosis of brain death.

OBJECTIVE: To prospectively compare three methods of apnea testing for the confirmation of brain death. DESIGN: Prospective, randomized, crossover study. SETTING: Intensive care unit of a tertiary care university hospital. PATIENTS: Twenty adult patients requiring apnea testing for confirmation of brain death. INTERVENTIONS: Ten minute apnea testing was repeated in random order for every patient with the three oxygenation systems: oxygen catheter inserted through the endotracheal tube (oxygen 6 L/min), T-piece system (oxygen 12 L/min), and continuous positive airway pressure (CPAP) system 10 cm H2O (oxygen 12 L/min). MEASUREMENTS AND MAIN RESULTS: Arterial blood was drawn at 0, 2, 5, and 10 mins of each test. Compared with baseline, Paco2 increased by 30.6 +/- 7.4, 30.0 +/- 7.3 and 30.2 +/- 7.5 mm Hg during the apnea period (p = .96), reaching 73.3 +/- 8.3, 71.6 +/- 11.1, and 72.7 +/- 9.0 mm Hg at the end of the apnea test (p = .73) for the oxygen catheter, the T-piece, and the CPAP, respectively. Pao2 decreased less with the CPAP compared with the oxygen catheter or the T-piece (-22.4 +/- 76, -99.1 +/- 158, and -91.6 +/- 133 mm Hg, respectively, p < .01). In two patients, apnea testing could not be completed with the oxygen catheter and the T-piece because of desaturation, although it could be completed with the CPAP. CONCLUSIONS: The T-piece and the CPAP systems are effective alternatives to the standard oxygen catheter technique for apnea testing. Oxygenation was best maintained with the CPAP system, which can be useful in some patients.

Discovery of an aurora on Mars.

In the high-latitude regions of Earth, aurorae are the often-spectacular visual manifestation of the interaction between electrically charged particles (electrons, protons or ions) with the neutral upper atmosphere, as they precipitate along magnetic field lines. More generally, auroral emissions in planetary atmospheres "are those that result from the impact of particles other than photoelectrons" (ref. 1). Auroral activity has been found on all four giant planets possessing a magnetic field (Jupiter, Saturn, Uranus and Neptune), as well as on Venus, which has no magnetic field. On the nightside of Venus, atomic O emissions at 130.4 nm and 135.6 nm appear in bright patches of varying sizes and intensities, which are believed to be produced by electrons with energy <300 eV (ref. 7). Here we report the discovery of an aurora in the martian atmosphere, using the ultraviolet spectrometer SPICAM on board Mars Express. It corresponds to a distinct type of aurora not seen before in the Solar System: it is unlike aurorae at Earth and the giant planets, which lie at the foot of the intrinsic magnetic field lines near the magnetic poles, and unlike venusian auroras, which are diffuse, sometimes spreading over the entire disk. Instead, the martian aurora is a highly concentrated and localized emission controlled by magnetic field anomalies in the martian crust.

Nightglow in the upper atmosphere of Mars and implications for atmospheric transport.

We detected light emissions in the nightside martian atmosphere with the SPICAM (spectroscopy for the investigation of the characteristics of the atmosphere of Mars) ultraviolet (UV) spectrometer on board the Mars Express. The UV spectrum of this nightglow is composed of hydrogen Lyman alpha emission (121.6 nanometers) and the gamma and delta bands of nitric oxide (NO) (190 to 270 nanometers) produced when N and O atoms combine to produce the NO molecule. N and O atoms are produced by extreme UV photodissociation of O2, CO2, and N2 in the dayside upper atmosphere and transported to the night side. The NO emission is brightest in the winter south polar night because of continuous downward transport of air in this region at night during winter and because of freezing at ground level.