Why is there so little water left on Mars?

By Franck Montmessin, Directeur de recherche CNRS au Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ) – Université Paris-Saclay

Mars is known for its thin atmosphere, where CO₂ dominates and provides most of the atmospheric mass and pressure. In fact, the pressure is similar to that in the Earth’s stratosphere, which is a layer of the atmosphere, at more than 30km above the surface.

But what about water? Water on Mars is currently found on the surface as a layer of ice – several kilometres thick – at the north pole. It also appears as seasonal frost at the coldest times of the year, and in the atmosphere as vapour and ice. Nevertheless,…

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