Analyzing the MLT region with mass spectrometers

The mesosphere and lower thermosphere (MLT) region is a key transition zone between Earth’s lower and upper atmospheres, where energetic processes, wave dynamics, and chemical reactions converge. Understanding the temperature and chemical composition in this region is crucial for interpreting processes at higher altitudes. Despite the MLT’s importance in mediating couplings between the lower and upper atmosphere, direct in-situ measurements are inherently challenging due to the low-density, high-altitude, and high-speed environment. However, recent advances in compact, high-sensitivity mass spectrometers offer novel opportunities to investigate some of the most pressing open questions in MLT research. In this work, we highlight how state-of-the-art mass spectrometry can address uncertainties in key processes governing the composition and temperature of the MLT. We outline how measurements of species such as atomic and molecular oxygen, molecular nitrogen, trace metals from meteoric or anthropogenic sources, and reactive radicals can inform MLT models. Our goal is to provide data that will enable the integration of mass spectrometry findings into a range of models, including regional and global climate models, that incorporate long-term measurements, potentially revealing hidden trends in chemical composition and temperature. Such temperature drifts could be indicative of climate change affecting this region of the atmosphere as well.