You Know it’s Spring on Mars When the Carbon Dioxide is Starting to Sublimate

The northern hemisphere of Mars is beginning to thaw from winter. But for the red planet, that doesn’t mean that birds will sing and flowers will bloom. It means that the carbon dioxide will sublimate. It’s still beautiful though.

Mars in its northern hemisphere is beginning to transition from winter to spring, where it will spend the next 6 months warming up. Observations with the HiRISE (High Resolution Imaging Experiment) onboard the Mars Reconnaissance Orbiter can see the first signs of this transition in the form of dark fans of soil in the northern polar regions.

The north polar ice cap of Mars is seasonal. It grows in the winter and fades in the summer. But it’s not a water ice cap like on the Earth – instead it’s made of frozen carbon dioxide, also known as dry ice. It also doesn’t grow and expand the same way as the ice caps on Earth do, which is by melting from solid to liquid.

Instead, in springtime the northern ice cap sublimates, with the carbon dioxide turning directly from a solid into a gas. This happens at different times from place to place, depending on how much sunlight each patch is getting. In some cases, a layer of ice can sublimate, expanding into a gas and exploding out as a thin jet above the surface. This jet carries with it dust, which spreads out in a fan-like pattern.

As the spring continues, more and more fans will appear until all the ice in the area has sublimated.

Not that summer on Mars is all that fun. At these latitudes you’ll be lucky to find a day above freezing, but at least it beats the winter time lows of -200°.