The Martian atmosphere is reported to contain over 95% carbon dioxide (CO2), so most of the ice and frost that forms around the planet's poles in winter is also CO2. In earlier studies, scientists suggested that "spiders" on Mars could form in the spring, when sunlight penetrates a translucent layer of carbon dioxide ice and heats the earth beneath it. Heating leads to the sublimation of ice - a process in which a solid is converted directly into a gas, bypassing the liquid stage. This cracks the ice and gas escapes through the cracks, leaving behind zigzag patterns that resemble spider legs.
Planetologists at the Open University of England were able to experimentally test this hypothesis using a device called a "Mars Simulation Camera", Live Science reports. Scientists have created in the laboratory a mini-version of "spiders" (real ones reach 1 kilometer in diameter) by placing sediment particles inside the chamber, and then dropping a piece of dry ice on them. When the cold ice touched a much warmer layer of Martian sediment, some of the ice instantly turned from solid to gas, forming spider cracks where the escaping gas seeped through the ice.
While these experiments are not conclusive, they provide the first evidence of where the "spiders" on Mars came from.
The research is published in Scientific Reports.