Evidence for transient morning water frost deposits on the Tharsis volcanoes of Mars
Adomas Valantinas, N. Thomas, A. Pommerol, Özgür Karatekin, Luca Ruiz Lozano, Cem Berk Senel, Orkun Temel, Ernst Hauber, Daniela Tirsch, Valentin Bickel, Giovanni Munaretto, M. Pajola, Fabrizio Oliva, Frédéric Schmidt, Ian Thomas, A. S. McEwen, Miguel Almeida, Matthew Read, Vidhya Ganesh Rangarajan, M. R. El‐Maarry, Cristina Re, F. G. Carrozzo, E. D’Aversa, Frank Daerden, Bojan Ristic, Manish Patel, G. Bellucci, J. J. López‐Moreno, Ann Carine Vandaele, G. Cremonese
Abstract
Abstract The present-day water cycle on Mars has implications for habitability and future human exploration. Water ice clouds and water vapour have been detected above the Tharsis volcanic province, suggesting the active exchange of water between regolith and atmosphere. Here we report observational evidence for extensive transient morning frost deposits on the calderas of the Tharsis volcanoes (Olympus, Arsia and Ascraeus Montes, and Ceraunius Tholus) using high-resolution colour images from the Colour and Stereo Surface Imaging System on board the European Space Agency’s Trace Gas Orbiter. The transient bluish deposits appear on the caldera floor and rim in the morning during the colder Martian seasons but are not present by afternoon. The presence of water frost is supported by spectral observations, as well as independent imagery from the European Space Agency’s Mars Express orbiter. Climate model simulations further suggest that early-morning surface temperatures at the high altitudes of the volcano calderas are sufficiently low to support the daily condensation of water—but not CO 2 —frost. Given the unlikely seasonal nature of volcanic outgassing, we suggest the observed frost is atmospheric in origin, implying the role of microclimate in local frost formation and a contribution to the broader Mars water cycle.