Our news today starts us out on the planet Mars and quickly brings us home to a Mars Simulation Chamber on Earth. I’m doing this story because it involves things called “Mars spiders” that, while not actually spiders, are still able to twig Beth’s arachnophobia. You have been warned.

For many years, orbiting space probes have spied strange features on Mars that appear like sponge paintings but are actually carved into the surface of Mars. It had been theorized that these features were caused by the sublimation of dry ice that had frozen in the soils over the Martian winter. Essentially, it gets so cold on Mars that, like a scene from The Day After Tomorrow, the air freezes solid; it just does so more slowly than in the movie, and it can end up in Martian soil. 

Unlike water ice, melting dry ice goes straight from solid to gas, leaving behind a dry void where the ice used to be. While the theory that these patterns, called Martian Spiders, are dry ice voids matches that we’re seeing, we haven’t been able to visit any with a rover and actually verify our theories. So scientists did the next best thing and recreated the formation of these features in a chamber pumped down to the same low temperatures and pressures of Mars. 

This work, published in Scientific Reports, was led by Lauren McKeown, who states: 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. 

Mystery solved, those spiders – which I really wish were called something else – are nothing more than a sign of the changing seasons.

More Information

Trinity College Dublin press release

“The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric pressure,” Lauren McKeown et al., 2021 March 19, Scientific Reports