Hélène Massager

Background

• BA in chemistry, ULB (2020-2024)
• MA in chemistry, ULB (2023-2025)
• Master thesis: "Observations des émissions d'éthylène du pipeline ouest iranien par les mesures du sondeur IASI", ULB (2025)
• PhD student in Sciences, ULB (2025-)

PhD project

Satellite measurements of hydrogen peroxide H2O2 in the atmosphere of Earth and Mars, for a better understanding of global oxidant budgets.

HOx radicals (OH and HO2) and their hydrogen peroxide (H2O2) reservoir play a central role in atmospheric chemistry, controlling the lifetime of greenhouse gases and many other air pollutants. The lack of routine global measurements of H2O2 in the lower troposphere is a long-standing gap in our ability to monitor and understand the atmosphere’s oxidative capacity. This PhD project addresses this gap directly by exploiting, for the first time, hyperspectral infrared sounders such as IASI and IASI-NG to detect and quantify H2O2 from space. After obtaining spectral evidence of the H2O2 signature in IASI spectra, this project aims to develop a robust retrieval algorithm for deriving H2O2 vertically integrated abundances from IASI(NG)-observed spectra, ultimately resulting in a unique global long-term dataset of bi-daily H2O2 distributions. The next part of this PhD is dedicated to the exploitation of this dataset. This includes characterizing the spatiotemporal variability of H2O2 on diurnal, seasonal, and multi-year timescales. Large plumes of H2O2 will be analyzed in combination with abundances of volatile organic compounds to study H2O2 production and the regeneration of HOx radicals. To assess and contribute to improving current atmospheric chemistry models, a detailed comparison will be made between IASI-derived H2O2 fields and the output from a state-of-the-art global atmospheric model. Like on Earth, H2O2 is also a very important compound in the atmosphere of Mars, where its abundance is closely linked to HOx radicals and water vapor abundance. The detection of H2O2 from Mars satellite observations will be attempted using the techniques developed for H2O2 detection and quantification in the Earth’s atmosphere adapted to measurements made by the PFS sounder of the Martian atmosphere.

Publications

See here.

Contact

Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES)(https://squares.ulb.be//),
Université Libre de Bruxelles, CP160/09
50 Av. F.D. Roosevelt, B-1050 Belgium
E-mail