The Composition and Chemistry of Titan's Atmosphere

In this review I summarize the current state of knowledge about the composition of Titan's atmosphere and our current understanding of the suggested chemistry that leads to that observed composition. I begin with our present knowledge of the atmospheric composition, garnered from a variety of measurements including Cassini-Huygens, the Atacama Large Millimeter/submillimeter Array, and other ground- and space-based telescopes. This review focuses on the typical vertical profiles of gases at low latitudes rather than global and temporal variations. The main body of the review presents a chemical description of how complex molecules are believed to arise from simpler species, considering all known "stable" molecules-those that have been uniquely identified in the neutral atmosphere. The last section of the review is devoted to the gaps in our present knowledge of Titan's chemical composition and how further work may fill those gaps.

Atmospheres of science: Experiencing scientific mobility

This article uses notions of the atmospheric to engage with empirical material concerned with international mobility in science. It draws on recent conceptual work on atmospheres that frames them as allowing access to the affective qualities of everyday life and as 'productively nebulous': atmospheres exist between the local and the globally diffuse, the emergent and the staged, the intangible and the brutally present. Using atmospheric thinking, I devise 'apparatuses of attunement' to capture elusive aspects of life in science, as discussed in interviews with natural scientists about their experiences of international mobility. In particular I use ideas of the situation, atmospheric threads, and the staging of atmospheres to argue that scientists represent themselves as existing in between the particular and the general: they are never wholly at the mercy of the structures and expectations of globalized science, but are also never not in the grip of them. In closing I reflect on what this analysis reveals about the affective qualities of contemporary science, the forms of life being nurtured by the norms and expectations of research (policy), and the kinds of agency available to (these) scientists. The aim of the article is thus twofold: to demonstrate how concepts of atmospheres can be put to work in STS, and to contribute to research on international mobility in science and contemporary scientific careers.

Virtual Terroir and the Premium Coffee Experience

With its origin-centric value proposition, the specialty coffee industry seeks to educate consumers about the value of the origin of coffee and how the relationship with farmers ensures quality and makes coffee a premium product. While the industry has widely used stories and visual cues to communicate this added value, research studying whether and how these efforts influence consumers' experiences is scarce. Through three experiments, we explored the effect of images that evoke the terroir of coffee on the perception of premiumness. Our results revealed that online images that resembled the broad origin of coffee (i.e., a farm) could influence premiumness expectations of coffee (Experiment 1). Similarly, a virtual reality environment that depicted this broad origin (vs. a control but not a city atmosphere) could enhance the perception of coffee premiumness for non-expert consumers (Experiment 2) and the enjoyment of the experience for coffee professionals (Experiment 3). Importantly, we found that congruence between the coffee and the virtual reality (VR) atmospheres mediated how much non-experts enjoyed the experience (Experiment 2). VR atmospheres also influenced expectations of sweetness and acidity for non-experts (Experiment 2). These findings serve as a steppingstone for further exploration of the effects of congruence between visual cues and product/brand attributes on premiumness expectations and perception, and more generally on consumer experience. From a practical standpoint, this study provides insights into key aspects for the development of immersive virtual product experiences.

The Limits of the City: Atmospheres of Lockdown

Criminological engagement with urban environments has burgeoned, including investigations into the criminological sense of place and into the atmospheres of crime and justice. This article analyses cities under lockdown in the 2020 COVID-19 pandemic. Used in numerous cities, lockdowns conjoin public health initiatives and crime control to restrict the location and activities of citizens. Drawing on textual and ethnographic exploration of lockdown in Melbourne, Australia, the article examines how we make meaning in lockdown through processes of sensory and spatial interpretation. Such an approach exposes both atmospheres of control, through the criminalization of everyday activities, and numerous instances of subversion through resistance to and adaptation of the spatial and sensorial characteristics of lockdown. The article argues for the importance of the sensory as a means of conceptualizing, repopulating and redesigning future cities after lockdown ends.

Atmospheric composition of exoplanets based on the thermal escape of gases and implications for habitability

The detection of habitable exoplanets is an exciting scientific and technical challenge. Owing to the current and most likely long-lasting impossibility of performing in situ exploration of exoplanets, their study and hypotheses regarding their capability to host life will be based on the restricted low-resolution spatial and spectral information of their atmospheres. On the other hand, with the advent of the upcoming exoplanet survey missions and technological improvements, there is a need for preliminary discrimination that can prioritize potential candidates within the fast-growing list of exoplanets. Here we estimate, for the first time and using the kinetic theory of gases, a list of the possible atmospheric species that can be retained in the atmospheres of the known exoplanets. We conclude that, based on our current knowledge of the detected exoplanets, 45 of them are good candidates for habitability studies. These exoplanets could have Earth-like atmospheres and should be able to maintain stable liquid water. Our results suggest that the current definition of a habitable zone around a star should be revisited and that the capacity of the planet to host an Earth-like atmosphere to support the stability of liquid water should be added.

Making home visits: Creativity and the embodied practices of home visiting in social work and child protection

Although the home is the most common place where social work goes on, research has largely ignored the home visit. Drawing on a participant observation study of child protection work, this article reveals the complex hidden practices of social work on home visits. It is argued that home visits do not simply involve an extension of the social work organisation, policies and procedures into the domestic domain but the home constitutes a distinct sphere of practice and experience in its own right. Home visiting is shown to be a deeply embodied practice in which all the senses and emotions come into play and movement is central. Through the use of creativity, craft and improvisation practitioners 'make' home visits by skilfully enacting a series of transitions from the office to the doorstep, and into the house, where complex interactions with service users and their domestic space and other objects occur. Looking around houses and working with children alone in their bedrooms were common. Drawing upon sensory and mobile methods and a material culture studies approach, the article shows how effective practice was sometimes blocked and also how the home was skilfully negotiated, moved around and creatively used by social workers to ensure parents were engaged with and children seen, held and kept safe.

Photochemistry on Pluto - I. Hydrocarbons and aerosols

In light of the recent New Horizons flyby measurements, we present a coupled ion-neutral-photochemistry model developed for simulating the atmosphere of Pluto. Our model results closely match the observed density profiles of CH4, N2 and the C2 hydrocarbons in the altitude range where available New Horizons measurements are most accurate (above ~ 100-200 km). We found a high eddy coefficient of 106 cm2 s-1 from the surface to an altitude of 150 km, and 3 × 106 cm2 s-1 above 150 km for Pluto's atmosphere. Our results demonstrate that C2 hydrocarbons must stick to and be removed by aerosol particles in order to reproduce the C2 profiles observed by New Horizons. Incorporation into aerosols in Pluto's atmosphere is a significantly more effective process than condensation, and we found that condensation alone cannot account for the observed shape of the vertical profiles. We empirically determined the sticking efficiency of C2 hydrocarbons to aerosol particles as a function of altitude, and found that the sticking efficiency of C2 hydrocarbons is inversely related to the aerosol surface area. Aerosols must harden and become less sticky as they age in Pluto's atmosphere. Such hardening with ageing is both necessary and sufficient to explain the vertical profiles of C2 hydrocarbons in Pluto's atmosphere. This result is in agreement with the fundamental idea of aerosols hardening as they age, as proposed for Titan's aerosols.

ANALYTICAL INVESTIGATION OF THE DECREASE IN THE SIZE OF THE HABITABLE ZONE DUE TO A LIMITED CO2 OUTGASSING RATE

The habitable zone concept is important because it focuses the scientific search for extraterrestrial life and aids the planning of future telescopes. Recent work has shown that planets near the outer edge of the habitable zone might not actually be able to stay warm and habitable if CO2 outgassing rates are not large enough to maintain high CO2 partial pressures against removal by silicate weathering. In this paper, I use simple equations for the climate and CO2 budget of a planet in the habitable zone that can capture the qualitative behavior of the system. With these equations I derive an analytical formula for an effective outer edge of the habitable zone, including limitations imposed by the CO2 outgassing rate. I then show that climate cycles between a snowball state and a warm climate are only possible beyond this limit if the weathering rate in the snowball climate is smaller than the CO2 outgassing rate (otherwise stable snowball states result). I derive an analytical solution for the climate cycles including a formula for their period in this limit. This work allows us to explore the qualitative effects of weathering processes on the effective outer edge of the habitable zone, which is important because weathering parameterizations are uncertain.

Influence of Inert and Oxidizing Atmospheres on the Physical and Optical Properties of Luminescent Carbon Dots Prepared through Pyrolysis of a Model Molecule

This work used L-tartaric acid as a model molecule to evaluate how the use of inert and oxidizing atmospheres during pyrolysis affected the physical and optical properties of the resulting carbon dots (CDs). Pyrolysis revealed to be a simple procedure that afforded CDs in a single step, dismissed the addition of organic solvents, and involved only one extraction stage that employed water. By X-ray diffraction a dependency between the structure of the CDs and the atmosphere (oxidizing or inert) used during the pyrolysis was found. Potentiometric titration demonstrated that the CDs were largely soluble in water; it also aided characterization of the various groups that contained sp(3) -hybridized carbon atoms on the surface of the dots. Raman spectroscopy suggested that different amounts of sp(2)- and sp(3)-hybridized carbon atoms emerged on the CDs depending on the pyrolysis atmosphere. In conclusion, the pyrolysis atmosphere influenced the physical properties, such as the composition and the final structure.

Atmospheres of progress in a data-based school

In this article, I seek to extend the geographies of education, youth and young people by offering an account of the significant shifts taking place in contemporary English state education around the production and use of data. I present material from pupils, for whom the changes are putatively made, whose voices are absent in existing educational and sociological literature on data in schools. I do this through an exploration of one specific feature of school datascapes: the use of data to create and maintain a sense of 'progress'. This is not progress solely as developmental fact, logic, ideology or discourse but as felt. This article draws attention to profound changes to cultures of education that are evinced in relation to contemporary proliferations of data, contributes to theorisations of affective atmospheres in geography and how they come to be known (as a question of both experience and method), and it advances a novel theorisation of progress 'after the affective turn'.

Prospects for detecting oxygen, water, and chlorophyll on an exo-Earth

The goal of finding and characterizing nearby Earth-like planets is driving many NASA high-contrast flagship mission concepts, the latest of which is known as the Advanced Technology Large-Aperture Space Telescope (ATLAST). In this article, we calculate the optimal spectral resolution R = λ/δλ and minimum signal-to-noise ratio per spectral bin (SNR), two central design requirements for a high-contrast space mission, to detect signatures of water, oxygen, and chlorophyll on an Earth twin. We first develop a minimally parametric model and demonstrate its ability to fit synthetic and observed Earth spectra; this allows us to measure the statistical evidence for each component's presence. We find that water is the easiest to detect, requiring a resolution R ≳ 20, while the optimal resolution for oxygen is likely to be closer to R = 150, somewhat higher than the canonical value in the literature. At these resolutions, detecting oxygen will require approximately two times the SNR as water. Chlorophyll requires approximately six times the SNR as oxygen for an Earth twin, only falling to oxygen-like levels of detectability for a low cloud cover and/or a large vegetation covering fraction. This suggests designing a mission for sensitivity to oxygen and adopting a multitiered observing strategy, first targeting water, then oxygen on the more favorable planets, and finally chlorophyll on only the most promising worlds.

Possible climates on terrestrial exoplanets

What kind of environment may exist on terrestrial planets around other stars? In spite of the lack of direct observations, it may not be premature to speculate on exoplanetary climates, for instance, to optimize future telescopic observations or to assess the probability of habitable worlds. To begin with, climate primarily depends on (i) the atmospheric composition and the volatile inventory; (ii) the incident stellar flux; and (iii) the tidal evolution of the planetary spin, which can notably lock a planet with a permanent night side. The atmospheric composition and mass depends on complex processes, which are difficult to model: origins of volatiles, atmospheric escape, geochemistry, photochemistry, etc. We discuss physical constraints, which can help us to speculate on the possible type of atmosphere, depending on the planet size, its final distance for its star and the star type. Assuming that the atmosphere is known, the possible climates can be explored using global climate models analogous to the ones developed to simulate the Earth as well as the other telluric atmospheres in the solar system. Our experience with Mars, Titan and Venus suggests that realistic climate simulators can be developed by combining components, such as a 'dynamical core', a radiative transfer solver, a parametrization of subgrid-scale turbulence and convection, a thermal ground model and a volatile phase change code. On this basis, we can aspire to build reliable climate predictors for exoplanets. However, whatever the accuracy of the models, predicting the actual climate regime on a specific planet will remain challenging because climate systems are affected by strong positive feedbacks. They can drive planets with very similar forcing and volatile inventory to completely different states. For instance, the coupling among temperature, volatile phase changes and radiative properties results in instabilities, such as runaway glaciations and runaway greenhouse effect.