Ah, springtime on Mars, when weird features stretch across the surface as the seasons change and temperatures start to rise. This time, NASA’s HiRISE has spotted some strange polygon-shaped patterns that make it look like Mars is draped in huge swathes of honeycomb.

No, these unusual features were not made by giant Martian bees – or spiders, if you are among those who think they look like huge webs – but rather from the continuous cycle of seasonal changes of water ice and carbon dioxide (CO₂). The polygons are created by frozen and thawed water ice.

Mars is a very cold planet thanks to a thin atmosphere and lack of oceans to moderate temperatures. In polar regions during the Martian winter, carbon dioxide freezes and builds up a thin layer of ice on the surface – essentially a layer of dry ice. When it melts, dry ice bypasses the liquid phase and turns directly from solid to gas. So, as spring comes around and the temperatures start to warm up, the ice turns from solid to vapor, a process called sublimation.

This process starts from the bottom up, as the ice is nearly transparent so the Sun’s rays can reach the bottom layer and heat up the surface below. As the bottom layer of the ice melts, it traps the resulting CO₂ between the sand and the ice above, building pressure. Sometimes it cracks, allowing the gas to escape in vents, as seen in blue above.

The escaping gas carries fine particles from the buried surface that further erode the surface dry ice. According to Candy Hansen in a HiRISE blog post: "The particles drop to the surface in dark fan-shaped deposits. Sometimes the dark particles sink into the dry ice, leaving bright marks where the fans were originally deposited." 

Curiously, the vents can close up and then open again, creating more than one fan originating from the same spot but oriented differently depending on which way the wind was blowing, Hansen writes.

HiRISE took this awesome photo of polygons forming on the ridges of sand dunes back in 2013. Scientists at the time noted that if the deposits of fine particles had become hardened they may not have been able to tell they were wind-blown dunes and may have interpreted them as a dried-up lake bed.

Mars isn't the only place in the Solar System that experiences these polygons either (and no, we don't just mean Earth). While carrying out a close flyby in 2015, New Horizons discovered Pluto has them too.