First Detection and Thermal Characterization of Terminator CO<sub>2</sub>Ice Clouds With ExoMars/NOMAD
Giuliano Liuzzi, Gerónimo Villanueva, Loïc Trompet, Matteo Crismani, Arianna Piccialli, Shohei Aoki, M. Á. López‐Valverde, Aurélien Stolzenbach, Frank Daerden, Lori Neary, M. D. Smith, Manish Patel, S. R. Lewis, R. T. Clancy, Ian Thomas, Bojan Ristic, G. Bellucci, J. J. López‐Moreno, Ann Carine Vandaele
Abstract
Abstract We present observations of terminator CO 2 ice clouds events in three groups: Equatorial dawn, Equatorial dusk (both between 20°S and 20°N) and Southern midlatitudes at dawn (45°S and 55°S east of Hellas Basin) with ESA ExoMars Trace Gas Orbiter's Nadir and Occultation for MArs Discovery instrument. CO 2 ice abundance is retrieved simultaneously with water ice, dust, and particle sizes, and rotational temperature and CO 2 column profiles in 16 of 26 cases. Small particles (<0.5 μm) prevail at dusk, while water ice likely provides most source nuclei at dawn. Clouds east of Hellas are found to be dominantly nucleated on surface‐lifted dust. CO 2 ice is sometimes detected in unsaturated air together with dust nuclei at dawn, suggesting ongoing sublimation. Depending on latitude and local time, the interplay between particle precipitation and the lifetime of temperature minima (i.e., cold pockets) determines CO 2 ice properties.