Earth Observation Data Group

Abstract:

Abstract The origin of water and volatile compounds on planets including Earth is a hotly debated topic in planetary science. For example, many dynamic models suggest that the majority of Earth’s water and volatile elements were added from an external source. The stellar wind irradiation of rocky oxygen-containing minerals results in a reaction between H+ ions and silicate minerals to produce water and OH, which could explain the presence of water in the regoliths of airless worlds such as the Moon, as well as the water abundances in asteroids. Here, we used the method of high-resolution infrared spectrometry and temperature-programmed desorption (TPD) with mass detection to observe and for the first time quantify water formation on the surfaces of oxygen-bearing minerals. We tested 14 different mineral and natural samples and observed the formation of water on their surfaces upon exposure to H+ or D+ irradiation. The samples, including two meteorite samples (RAS 445 and SAU 567), were shown to have a water adsorption capacity between 0.09 and 0.7 wt%. The adsorbed water (likely dissociatively adsorbed) remains on the surface at pressures as low as 10−9 mbar (in the TPD experiment) and temperatures as high as 600 K, which suggests a possible transfer over long distances and timescales. Our article has a general character and demonstrates that any interaction of oxygen-containing minerals with stellar radiation (H+ ions) leads to the generation of water adsorbed on the surface of the minerals. The case of the origin of water on Earth is taken as a prime example.

Abstract:

Coarse mineral dust particles have been observed much further from the Sahara than expected based on theory. They have impacts different to finer particles on Earth's radiative budget, as well as carbon and hydrological cycles, though they tend to be under-represented in climate models. We use measurements of the full dust size distribution from aircraft campaigns over the Sahara, Canaries, Cabo Verde and Caribbean. We assess the observed and modelled dust size distribution over long-range transport at high vertical resolution using the Met Office Unified Model, which represents dust up to 63.2 µm diameter, greater than most climate models. We show that the model generally replicates the vertical distribution of the total dust mass but transports larger dust particles too low in the atmosphere. Importantly, coarse particles in the model are deposited too quickly, resulting in an underestimation of dust mass that is exacerbated with westwards transport; the 20–63 µm dust mass contribution between 2 and 3.7 km altitude is underestimated by factors of up to 11 in the Sahara, 140 in the Canaries and 240 in Cabo Verde. In the Caribbean, there is negligible modelled contribution of d  > 20 µm particles to total mass, compared to 10 % in the observations. This work adds to the growing body of research that demonstrates the need for a process-based evaluation of climate model dust simulations to identify where improvements could be implemented.

Abstract:

The goal of this white paper is to provide a snapshot of the data availability and data needs primarily for the Ariel space mission, but also for related atmospheric studies of exoplanets and cool stars. It covers the following data-related topics: molecular and atomic line lists, line profiles, computed cross-sections and opacities, collision-induced absorption and other continuum data, optical properties of aerosols and surfaces, atmospheric chemistry, UV photodissociation and photoabsorption cross-sections, and standards in the description and format of such data. These data aspects are discussed by addressing the following questions for each topic, based on the experience of the ‘data-provider’ and ‘data-user’ communities: (1) what are the types and sources of currently available data, (2) what work is currently in progress, and (3) what are the current and anticipated data needs. We present a GitHub platform for Ariel-related data, with the goal to provide a go-to place for both data-users and data-providers, for the users to make requests for their data needs and for the data-providers to link to their available data. Our aim throughout the paper is to provide practical information on existing sources of data whether in data bases, theoretical, or literature sources.