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Seasonal changes in Mars’ atmosphere proving a mystery

Mars surface

15 November 2019

Researchers have found the large variations in the levels of oxygen present on Mars cannot be explained by known chemistry.


Muriel Cozier

Like the Earth, Mars has seasonal changes. However each season on Mars is nearly twice as long as on Earth due to its orbital period of 687 days.

Seasonal changes in Mars’ meteorological parameters have been monitored by various spacecraft since 1976 resulting in an extensive record of the planet’s surface temperature and pressure. Curiosity rover, the current space craft sending back data is measuring other environmental properties including aerosol opacity, UV flux and water vapour content.

An international team of scientists have now been able to complete the first multi-year in situ measurements of the major components of the Mars atmosphere from the Sample Analysis at Mars instrument on board the Mars Science Laboratory, Curiosity.  Their findings have been published in Journal of Geophysical Research: Planets.

Measuring changes in gases that fill the atmosphere around the Gale crater, where Curiosity landed, scientists found that the atmosphere comprised carbon dioxide 95.1%, nitrogen 2.59%, argon 1.94% oxygen, 0.161% and carbon monoxide 0.058%.

However it was discovered that the abundance of the gases varied by up to 40% throughout the year, due the seasonal cycle. Oxygen was observed to show the most significant seasonal and year-to-year variability, which the scientists believe is due to an ‘unknown atmospheric or surface process at work.’

The surprising seasonal an inter-annual variation in oxygen above the Gale crater cannot be accounted for in current chemical models, researchers conclude.

Though Mars has the potential to generate significant oxygen release due an abundance of oxidants in and at its surface, the mechanisms by which the oxygen could be quickly generated and then quickly destroyed are completely unknown.

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