Boffins believe they've made a breakthrough on what the 'giant spiders' on Mars' surface are.
The strange alien patterns spotted on the Red Planet's south pole 20 years ago baffled scientists as they don't resemble anything on Earth.
However, a new study describes how scientists successfully recreated a smaller version of the spiders in their lab.
By using a slab of carbon dioxide ice – also known as dry ice – and a machine that simulates the atmosphere on Mars, they've found it to be gas.
When the cold ice made contact with the warmer bed of Mars-like sediment, part of the ice transformed from a solid to a gas, referred to as sublimation, reports Space.com.
The process formed spidery cracks where the escaping gas pushed through the ice, claims a report in the journal Scientific Reports.
"This research presents the first set of empirical evidence for a surface process that is thought to modify the polar landscape on Mars ," lead study author Lauren McKeown said.
The planetary scientist at the Open University in England added: "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. "
More than 95% of the Martian atmosphere contains carbon dioxide (CO2), states NASA.
The ice and frost that form around the south and north poles in winter are also made of CO2.
Researchers hypothesised that the spiders on the Red Planet could also form in the spring, when sunlight penetrates the layer of CO2 ice and warms the surface underneath, reports a study back in 2003.
The heating causes pressure to build up under the ice until it finally cracks.
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The gas then escapes through the cracks and leaves behind a zig-zag pattern, which we can see on Mars today.
Until now, boffins had no way of testing the hypothesis here on Earth where the atmospheric conditions are different.
But researchers managed to 'make a little piece of Mars by using a simulation chamber and placed sediment grains of varying size inside.
While not definitive until researchers are able to examine the spiders on Mars themselves, the experiences provide the first physical evidence showing how they may have formed.
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