Global Vertical Distribution of Water Vapor on Mars: Results From 3.5 Years of ExoMars-TGO/NOMAD Science Operations

We present water vapor vertical distributions on Mars retrieved from 3.5 years of solar occultation measurements by Nadir and Occultation for Mars Discovery onboard the ExoMars Trace Gas Orbiter, which reveal a strong contrast between aphelion and perihelion water climates. In equinox periods, most of water vapor is confined into the low-middle latitudes. In aphelion periods, water vapor sublimated from the northern polar cap is confined into very low altitudes-water vapor mixing ratios observed at the 0-5 km lower boundary of measurement decrease by an order of magnitude at the approximate altitudes of 15 and 30 km for the latitudes higher than 50°N and 30-50°N, respectively. The vertical confinement of water vapor at northern middle latitudes around aphelion is more pronounced in the morning terminators than evening, perhaps controlled by the diurnal cycle of cloud formation. Water vapor is also observed over the low latitude regions in the aphelion southern hemisphere (0-30°S) mostly below 10-20 km, which suggests north-south transport of water still occurs. In perihelion periods, water vapor sublimated from the southern polar cap directly reaches high altitudes (>80 km) over high southern latitudes, suggesting more effective transport by the meridional circulation without condensation. We show that heating during perihelion, sporadic global dust storms, and regional dust storms occurring annually around 330° of solar longitude (L _S) are the main events to supply water vapor to the upper atmosphere above 70 km.

Martian CO2 Ice Observation at High Spectral Resolution With ExoMars/TGO NOMAD

The Nadir and Occultation for MArs Discovery (NOMAD) instrument suite aboard ExoMars/Trace Gas Orbiter spacecraft is mainly conceived for the study of minor atmospheric species, but it also offers the opportunity to investigate surface composition and aerosols properties. We investigate the information content of the Limb, Nadir, and Occultation (LNO) infrared channel of NOMAD and demonstrate how spectral orders 169, 189, and 190 can be exploited to detect surface CO₂ ice. We study the strong CO₂ ice absorption band at 2.7 μm and the shallower band at 2.35 μm taking advantage of observations across Martian Years 34 and 35 (March 2018 to February 2020), straddling a global dust storm. We obtain latitudinal-seasonal maps for CO₂ ice in both polar regions, in overall agreement with predictions by a general climate model and with the Mars Express/OMEGA spectrometer Martian Years 27 and 28 observations. We find that the narrow 2.35 μm absorption band, spectrally well covered by LNO order 189, offers the most promising potential for the retrieval of CO₂ ice microphysical properties. Occurrences of CO₂ ice spectra are also detected at low latitudes and we discuss about their interpretation as daytime high altitude CO₂ ice clouds as opposed to surface frost. We find that the clouds hypothesis is preferable on the basis of surface temperature, local time and grain size considerations, resulting in the first detection of CO₂ ice clouds through the study of this spectral range. Through radiative transfer considerations on these detections we find that the 2.35 μm absorption feature of CO₂ ice clouds is possibly sensitive to nm-sized ice grains.

The Oxford space environment goniometer: A new experimental setup for making directional emissivity measurements under a simulated space environment

Measurements of the light scattering behaviour of the regoliths of airless bodies via remote sensing techniques in the Solar System, across wavelengths from the visible to the far infrared, are essential in understanding their surface properties. A key parameter is knowledge of the angular behaviour of scattered light, usually represented mathematically by a phase function. The phase function is believed to be dependent on many factors including the following: surface composition, surface roughness across all length scales, and the wavelength of radiation. Although there have been many phase function measurements of regolith analog materials across visible wavelengths, there have been no equivalent measurements made in the thermal infrared (TIR). This may have been due to a lack of TIR instruments as part of planetary remote sensing payloads. However, since the launch of Diviner to the Moon in 2009, OSIRIS-Rex to the asteroid Bennu in 2016, and the planned launch of BepiColombo to Mercury in 2018, there is now a large quantity of TIR remote sensing data that need to be interpreted. It is therefore important to extend laboratory phase function measurements to the TIR. This paper describes the design, build, calibration, and initial measurements from a new laboratory instrument that is able to make phase function measurements of analog planetary regoliths across wavelengths from the visible to the TIR.

Optical and radiometric models of the NOMAD instrument part II: the infrared channels - SO and LNO

NOMAD is a suite of three spectrometers that will be launched in 2016 as part of the joint ESA-Roscosmos ExoMars Trace Gas Orbiter mission. The instrument contains three channels that cover the IR and UV spectral ranges and can perform solar occultation, nadir and limb observations, to detect and map a wide variety of Martian atmospheric gases and trace species. Part I of this work described the models of the UVIS channel; in this second part, we present the optical models representing the two IR channels, SO (Solar Occultation) and LNO (Limb, Nadir and Occultation), and use them to determine signal to noise ratios (SNRs) for many expected observational cases. In solar occultation mode, both the SO and LNO channel exhibit very high SNRs >5000. SNRs of around 100 were found for the LNO channel in nadir mode, depending on the atmospheric conditions, Martian surface properties, and observation geometry.

A new experimental setup for making thermal emission measurements in a simulated lunar environment

One of the key problems in determining lunar surface composition for thermal-infrared measurements is the lack of comparable laboratory-measured spectra. As the surface is typically composed of fine-grained particulates, the lunar environment induces a thermal gradient within the near sub-surface, altering the emission spectra: this environment must therefore be simulated in the laboratory, considerably increasing the complexity of the measurement. Previous measurements have created this thermal gradient by either heating the cup in which the sample sits or by illuminating the sample using a solar-like source. This is the first setup able to measure in both configurations, allowing direct comparisons to be made between the two. Also, measurements across a wider spectral range and at a much higher spectral resolution can be acquired using this new setup. These are required to support new measurements made by the Diviner Lunar Radiometer, the first multi-spectral thermal-infrared instrument to orbit the Moon. Results from the two different heating methods are presented, with measurements of a fine-grained quartz sample compared to previous similar measurements, plus measurements of a common lunar highland material, anorthite. The results show that quartz gives the same results for both methods of heating, as predicted by previous studies, though the anorthite spectra are different. The new calibration pipeline required to convert the raw data into emissivity spectra is described also.

Use of Baby Check to assess the severity of illness in babies attending a clinic in The Gambia

Baby Check is a systematic way of grading the severity of illness in infants. We studied its usefulness for assessing 53 infants presenting to a clinic in a West African village. Their ages ranged from 2 weeks to 7 months. The Baby Check scores ranged from 0 to 30. Forty-four infants were considered by the doctors to be well or mildly ill, 41 of these had scores below 9. The three infants with higher scores had symptoms and signs suggesting they were more than mildly ill. Nine infants were considered to be moderately ill. Their scores ranged from 4 to 30. The babies with the low scores had few symptoms and diagnoses suggesting they were only mildly ill. The babies with the highest scores all had diagnoses requiring medical attention. This pilot study of Baby Check in a developing country suggests that its use by health workers could increase the accuracy with which babies are referred for a medical opinion, and be a valuable tool for the identification of such infants in a busy clinic.

Acute oxygen toxicity in a saturation diver working in the North Sea

A commercial diver taking part in a saturation dive (O2-He) was exposed intermittently to 1.4 b of oxygen for a total of 55 h. He developed the syndrome associated with oxygen pulmonary toxicity. Detailed pulmonary function spirometry tests before and after the incident showed that a significant decrease in the forced vital capacity and forced expired volume in 1 s occurred and full recovery was at this time not present 12 weeks after the incident, although by this time he demonstrated a high state of cardiopulmonary fitness. These findings indicate that the lung damage caused by acute oxygen toxicity take more than 12 weeks to disappear, but the condition does seem to be reversible.