The frost is believed to represent 150,000 tonnes of water swapping between the surface and atmosphere of Mars each day during the cold seasons and could help scientists learn more about the red planet.
Scientists have discovered frost on Mars’ equator for the first time – a region where spotting frost was assumed to be impossible.
The water frost was spotted on the top of the Tharsis volcanoes, the tallest volcanoes we know of in the entire solar system – some of them are three times taller than Mount Everest. The patches of frost are present for a few hours around sunrise before they evaporate in sunlight.
The frost was detected by the European Space Agency’s ExoMars mission – specifically its Trace Gas Orbiter (TGO) – and later by an instrument on the Mars Express spacecraft. The ice covering is believed to be thin – roughly as thick as a human hair – but covers a vast area.
The researchers believe the frost represents an estimated 150,000 tonnes of water swapping between surface and atmosphere each day during the cold seasons.
“We thought it was impossible for frost to form around Mars’s equator, as the mix of sunshine and thin atmosphere keeps temperatures relatively high at both surface and mountaintop – unlike what we see on Earth, where you might expect to see frosty peaks,” says postdoctoral researcher and lead author of the study Dr Adomas Valantinas.
“Its existence here is exciting, and hints that there are exceptional processes at play that are allowing frost to form.”
This image shows Olympus Mons, the tallest volcano not only on Mars but in the entire solar system. Image: ESA
It is believed the cause of this vast amount of frost is due to calderas, which are large hollows at the summit of these Tharsis volcanoes, caused by earlier eruptions from magma chambers. The researchers believe that air circulates in a peculiar way above Tharsis, which creates a unique microclimate within the calderas of the volcanoes that allows the frost to form.
Valantinas explained the likely reasons that the frost has not been discovered until now – one being that researchers need an orbit that observes the location in the early morning.
“While ESA’s two Mars orbiters – Mars Express and TGO – have such orbits and can observe at all times of day, many from other agencies are instead synchronised to the sun and can only observe in the afternoon,” Valantinas said.
“Secondly, frost deposition is linked to colder martian seasons, making the window for spotting it even narrower. In short, we have to know where and when to look for ephemeral frost.
“We happened to be looking for it near the equator for some other research, but didn’t expect to see it on Mars’s volcano tops.”
By modelling how the frost forms on these volcanoes, it is hoped that scientists can learn more about Mars, such as where water exists, how it moves between reservoirs and details of the planet’s complex atmospheric dynamics.
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