Fig. 2: Seasonal variation of H density and H escape at the exobase.
From: Out-of-season water escape during Mars' northern summer triggered by a strong localized dust storm
Seasonal variation of (first row) the average Mars Ly β brightness, (second row) hydrogen density, (third row) derived hydrogen escape rate as observed by EMM/EMUS and (bottom) water vapor VMR retrieved by NOMAD at 60 km at latitudes above 50°N during MYs 36 and 37. Both the hydrogen density and loss rate are the ones at the exobase. The Mars Ly β emission has been corrected for the solar illumination as inferred from MAVEN/EUVM so that time periods with illumination differences due to solar rotation and the solar cycle can be directly compared. The increase in sun-corrected Ly β brightness at LS ~ 100° in MY 37 following the dust event is a model-independent indicator of an increase in the abundance/temperature of hydrogen in the Mars upper atmosphere, indicating enhanced H escape at this time. The solid lines show the smoothing of the data. The shaded areas indicate (red) the period where the water vapor increase is observed in MY 37 at LS=105°-130°, and (green) the end of the year C-storm season. For each magnitude, the right hand side panels show the ratio of the values within the shaded areas between MYs 36 and 37. The red line indicates the ratio during the same period in both MYs (red shaded areas), whereas the green line indicates the ratio between the peak within the red shaded area in M 37 and the mean value within the green area.
