Irish researchers prove Mars ‘spider patterns’ formed by dry ice turning to gas

Irish researchers have managed to present the first physical proof that the spidery shadows observed on the surface of Mars are formed by dry ice turning to gas.

Scientists from Trinity College Dublin have been able to prove a long-established hypothesis about Mars’ spider patterns by re-creating the planet’s atmosphere in a lab outside of London.

Araneiforms, more commonly referred to as “spiders from Mars” are negative topography features believed to be carved into the Martian surface by the sublimation (the switch from a solid to a gas) of dry ice during the springtime.

Unlike Earth, the Mars atmosphere comprises mainly carbon dioxide, which deposits on the planet’s surface as CO2 ice and frost (dry ice) as temperatures drop in winter.

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The Trinity team, along with scientists at Durham University in England and Britain’s Open University, conducted a series of experiments at the Open University Mars Simulation Chamber under Martian atmospheric pressure to investigate whether similar patterns could be achieved by the sublimation of dry ice.

Funded by the Irish Research Council and Europlanet, the scientists drilled holes in the centres of CO2 ice blocks and suspended them above beds of grains. Under Martian atmospheric pressure, the blocks formed a gaseous layer around themselves upon hitting the sandy surface.

In each case once the block was lifted it left behind it an eroded spider pattern. Sublimation was “much more vigorous than expected”, the researchers said, and material was thrown all over the chamber.

Lead researcher Dr Lauren McKeown of Trinity College said the findings present the “first set of empirical evidence” for a surface process that is believed to modify the polar landscape on Mars.

Kieffer’s hypothesis, which has been well accepted for over a decade, has, until now, only been framed in a purely theoretical context, she explained. Kieffer’s theory, which suggests sunlight heats the CO2 ice and transforms it into a gas, has never been directly observed on Mars.

“The experiments show directly that the spider patterns we observe on Mars from orbit can be carved by the direct conversion of dry ice from solid to gas. It is exciting because we are beginning to understand more about how the surface of Mars is changing seasonally today,” she went on.

Supervising the Ph.D research, Dr Mary Bourke of Trinity’s Geography Department said the findings could be informative for any future robotic or human exploration of the planet.