Strong Localized Pumping of Water Vapor to High Altitudes on Mars During the Perihelion Season

Here we present water vapor vertical profiles observed with the ExoMars Trace Gas Orbiter/Nadir and Occultation for MArs Discovery instrument during the perihelion and Southern summer solstice season (L_S = 240°–300°) in three consecutive Martian Years 34, 35, and 36. We show the detailed latitudinal distribution of H₂O at tangent altitudes from 10 to 120 km, revealing a vertical plume at 60°S–50°S injecting H₂O upward, reaching abundance of about 50 ppmv at 100 km. We have observed this event repeatedly in the three Martian years analyzed, appearing at L_S = 260°–280° and showing inter-annual variations in the magnitude and timing due to long term effects of the Martian Year 34 Global Dust Storm. We provide a rough estimate of projected hydrogen escape of 3.2 × 10⁹ cm⁻²s⁻¹ associated to these plumes, adding further evidence of the key role played by the perihelion season in the long term evolution of the planet's climate.