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Arthur T Knackerbracket has processed the following story:

Sea salt embedded in the dusty surface of Mars and lofted into the planet’s atmosphere has led to the discovery of hydrogen chloride – the first time the ESA-Roscosmos ExoMars Trace Gas Orbiter has detected a new gas. The spacecraft is also providing new information about how Mars is losing its water.

A major quest in Mars exploration is hunting for atmospheric gases linked to biological or geological activity, as well as understanding the past and present water inventory of the planet, to determine if Mars could ever have been habitable and if any water reservoirs could be accessible for future human exploration. Two new results from the ExoMars team published today in Science Advances unveil an entirely new class of chemistry and provide further insights into seasonal changes and surface-atmosphere interactions as driving forces behind the new observations.

“We’ve discovered hydrogen chloride for the first time on Mars. This is the first detection of a halogen gas in the atmosphere of Mars, and represents a new chemical cycle to understand,” says Kevin Olsen from the University of Oxford, UK, one of the lead scientists of the discovery.

[...] “You need water vapor to free chlorine and you need the by-products of water – hydrogen ­– to form hydrogen chloride. Water is critical in this chemistry,” says Kevin. “We also observe a correlation to dust: we see more hydrogen chloride when dust activity ramps up, a process linked to the seasonal heating of the southern hemisphere.”

[...] As well as new gases, the Trace Gas Orbiter is refining our understanding of how Mars lost its water – a process that is also linked to seasonal changes.

[...] Understanding the interplay of potential water-bearing reservoirs and their seasonal and long-term behavior is key to understanding the evolution of the climate of Mars. This can be done through the study of water vapour and ‘semi-heavy’ water (where one hydrogen atom is replaced by a deuterium atom, a form of hydrogen with an additional neutron).

[...] The ESA-Roscosmos ExoMars Trace Gas Orbiter studies water vapour and its components as it rises through the atmosphere and out into space. By looking specifically at the ratio of hydrogen to its heavier counterpart deuterium, the evolution of water loss over time can be traced. Credit: ESA

[...] “The changing seasons on Mars, and in particular the relatively hot summer in the southern hemisphere seems to be the driving force behind our new observations such as the enhanced atmospheric water loss and the dust activity linked to the detection of hydrogen chloride, that we see in the two latest studies,” adds Håkan. “Trace Gas Orbiter observations are enabling us to explore the martian atmosphere like never before.”

Journal References:
1.) Oleg Korablev, Kevin S. Olsen, Alexander Trokhimovskiy, et al. Transient HCl in the atmosphere of Mars [open], Science Advances (DOI: 10.1126/sciadv.abe4386)
2.) Geronimo L. Villanueva, Giuliano Liuzzi, Matteo M. J. Crismani, et al. Water heavily fractionated as it ascends on Mars as revealed by ExoMars/NOMAD [open], Science Advances (DOI: 10.1126/sciadv.abc8843)

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