Seasonal variability of water in the martian atmosphere

Seasonal variability of water (left) and D/H (right) for the northern (top) and southern (bottom) hemispheres, as determined by the Nadir and Occultation for MArs Discovery (NOMAD) instrument onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter.

Water is observed to reach high altitudes of greater than 80 km during regional and global dust storms, and at the onset of southern summer (labeled ‘aspirator’ from the latin word to aspire, or rise/climb up). Colder temperatures at the poles and in the middle atmosphere lead to fractionation of water and an apparent decrease of the D/H. Yet, when water is fully vapourised, it displays a strong enrichment of six times that of Earth’s oceans, confirming that large amounts of water have been lost to space over time.

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