https://orfeo.belnet.be/handle/internal/15 2026-04-13T19:45:33Z 2026-04-13T19:45:33Z Pacaud, R. Matéo-Vélez, J.-C. Hess, S. Ranvier, S. https://orfeo.belnet.be/handle/internal/14652 2026-04-03T10:52:11Z

Measurement of bipolar charge distribution of lunar dust simulant under VUV irradiation Pacaud, R.; Matéo-Vélez, J.-C.; Hess, S.; Ranvier, S. Upcoming missions to the Moon represent new science opportunities and challenges. The electrostatic nature of the regolith combined with the solar wind makes it loft and adhere to almost any surface, which represents a threat for future manned and robotic missions. Understanding the charge state of the lunar soil under a representative environment is a key step towards ensuring safe lunar missions. While the global first order effect of exposure to the Sun's UV is to charge the soil positively, past experiments suggested that the transported dusts could be charged negatively. This counter-intuitive behavior was then supported by modeling, which explained the existence of negative charges but also predicted that of positively charged ones. To investigate the charging behavior of dust under a representative environment, we developed an experimental protocol based on a polarized sensitive sensor dedicated to the charge measurement of single dust grains with an accuracy of about 1 fC. The first set of measurements obtained with JSC-1A lunar dust simulants in high vacuum reveals the bipolar nature of lunar dust net charge in the regolith when exposed to UVs. Indeed, both positive and negative dusts were detected, supporting the complexity of the regolith charging processes suggested by the models.

Friedrich, M. Koopman, S.J. Lin, Y. Mahieu, E. Smeekes, S. De Mazière, M. Flood, V. Frey, M.M. Grutter, M. Hannigan, J.. Hase, F. Jones, N. Kivi, R. Makarova, M. Morino, I. Murata, I. Nagahama, T. Notholt, J. Ortega, I. Prignon, M. Röhling, A.N. Smale, D. Strong, K. Té, Y. Zhou, M. https://orfeo.belnet.be/handle/internal/14651 2026-04-03T10:51:30Z

Identifying trend reversals in atmospheric ethane from a multi-site analysis Friedrich, M.; Koopman, S.J.; Lin, Y.; Mahieu, E.; Smeekes, S.; De Mazière, M.; Flood, V.; Frey, M.M.; Grutter, M.; Hannigan, J..; Hase, F.; Jones, N.; Kivi, R.; Makarova, M.; Morino, I.; Murata, I.; Nagahama, T.; Notholt, J.; Ortega, I.; Prignon, M.; Röhling, A.N.; Smale, D.; Strong, K.; Té, Y.; Zhou, M. Ethane is the most abundant non-methane hydrocarbon in Earth’s atmosphere and acts as an indirect greenhouse gas, influencing the atmospheric lifetime of methane. Therefore, understanding the development of trends and identifying trend reversals in atmospheric ethane is crucial. Ethane abundance is measured at different ground-based stations worldwide using Fourier transform infrared remote sensing techniques. We compile a new dataset comprising 26 ethane time series from the Northern and Southern Hemispheres. We analyze their long-term trends using different econometric techniques capable of handling missing data and strong seasonal components present in the data. The resulting trend patterns are consistent across the different methods, with similar estimated trends at the various stations. In the Northern Hemisphere, the common trend across stations declined from the 1990s to 2005, gradually increased over the next decade, and then resumed a similar downward trajectory from 2015 onward. The estimated trends reveal a pronounced peak around 2014/2015, marking a reversal from an upward to a downward trend.

Pierrard, V. Winant, A. https://orfeo.belnet.be/handle/internal/14641 2026-03-24T10:01:31Z

Atmospheric Loss of Energetic Electrons and Protons from the Radiation Belts After the Exceptional Injection of the 11 May 2024 Superstorm Leading to Four Electron Belts Pierrard, V.; Winant, A. The exceptionally strong geomagnetic storm of 10–11 May 2024 injected new energetic protons and electrons into the terrestrial radiation belts, creating extraordinary conditions to study the loss mechanisms scattering these particles into the atmosphere after the storm. For the first time, four electron belts were observed during several weeks. We show that this structure was due to electron loss, highly dependent on specific positions. Using the proton and electron fluxes measured by the Energetic Particle Telescope, EPT, on board PROBA-V, we determine the lifetimes of these populations depending on their energy ranges and positions. We show that the lifetimes are much longer for protons than for electrons, which enables us to determine their time variations independently. For electrons, the wave–particle loss mechanisms depend on the background ionosphere–plasmasphere density. The lifetimes determined after the May 2024 and 10 October 2024 big events are compared with average ones to understand their unusual specificity for the formation of four and three belts, respectively. For the injected protons of 9.5 to 13 MeV, the lifetime is minimum at L~1.9, where the fluxes are maximum, showing a lifetime depending on the flux intensity. Loss is due to pitch angle diffusion and collisions with electrons and nuclei in the ambient plasma and neutral atmosphere. At the outer edge of the proton belt, the flux is depleted at all energies after the geomagnetic perturbation, and we determine that the progressive time of refilling after the storm generally reaches more than 40 days. There is an excellent discrimination between the different populations of energetic electrons (0.5–8 MeV) and the injected protons (9.5–13 MeV) that are still observed several months after the event. Such results contribute to advancing understanding of the interactions between the terrestrial atmosphere and space radiation.

Aoki, S. Fujii, Y. Sagawa, H. Villanueva, G.L. Thomas, I. Ristic, B. Daerden, F. López-Valverde, M.A. Patel, M.R. Mason, J. Willame, Y. Bellucci, G. Vandaele, A.C. https://orfeo.belnet.be/handle/internal/14640 2026-03-24T10:02:03Z

Anatomy of Empirical Transit Spectra of Mars Based on TGO/NOMAD Aoki, S.; Fujii, Y.; Sagawa, H.; Villanueva, G.L.; Thomas, I.; Ristic, B.; Daerden, F.; López-Valverde, M.A.; Patel, M.R.; Mason, J.; Willame, Y.; Bellucci, G.; Vandaele, A.C. Transit spectroscopy is a powerful tool for probing atmospheric structures of exoplanets. Accurately accounting for the effects of aerosols is key to reconstructing atmospheric properties from transit spectra, yet this remains a significant challenge. To advance this effort, it is invaluable to examine the spectral features of well-characterized planetary atmospheres. Here, we synthesize empirical transit spectra of Mars across different seasons based on data from the NOMAD’s Solar Occultation channel on board ExoMars/TGO, which operates at wavelengths of 0.2–0.65 and 2–4 μm. In the generated empirical transit spectra, the atmosphere below 25 km is found to be largely opaque due to the presence of micron-sized dust and H2O ice clouds, both of which substantially weaken spectral features. The spectra exhibit CO2 absorption features at 2.7–2.8 μm and signatures of submicron-sized mesospheric H2O ice clouds around 3.1 μm, accompanied by a continuum slope. The amplitudes of these spectral features are found to vary with the Martian seasons, where the dust storms weaken the CO2 signatures and strengthen the H2O ice features, which serve as potential indicators of a dusty planet like Mars. If TRAPPIST-1f possessed a Mars-like atmospheric structure, both CO2 and H2O ice features would be detectable at a noise level of 3 ppm, a level likely beyond current observational capabilities. Nevertheless, the 3.1 μm feature produced by submicron-sized mesospheric H2O ice clouds offers a novel avenue for characterizing the atmospheres of habitable-zone exoplanets.