Gravity waves and heat in Mars’s atmosphere

Gravity waves and heat in Mars’s atmosphere. Atmospheric gravity waves arise when mountains and other massive features cause a wind’s otherwise smooth horizontal flow to oscillate vertically. On Mars, where the topography is rough and high and where wind speeds can reach 400 km/s, gravity waves carry momentum fluxes that far exceed those of their terrestrial counterparts. A new computational study demonstrates that gravity waves not only perturb the Martian atmosphere’s dynamics, as one would expect, but also perturb its thermal structure. Aymeric Spiga of the Pierre and Marie Curie University in Paris and his collaborators sought to explain a puzzling observation made in 1997 by Mars Pathfinder. As the lander parachuted toward the Martian surface, its sensors detected pockets of air whose anomalously low temperature (around 100 K) was cold enough for carbon dioxide, the atmosphere’s main constituent, to condense. Ice clouds of CO₂ were indeed detected...