Cookies and cream ice cream? Artisanal rippled white chocolate? Or springtime on Mars? This stunning image actually captures what happens when springtime arrives on everyone’s favorite Red Planet. Who knew Mars could look so delicious?
Taken on May 25 by the joint ESA/Roscosmos ExoMars Trace Gas Orbiter’s CaSSIS camera, it shows the explosive activity that creates the distinctive black streaks across the creamy sand dunes of Mars’ north pole region as the temperatures warm up and the winter ice begins to melt.
A thin atmosphere and lack of oceans to moderate temperatures make Mars a very cold planet. In the 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. Dry ice when it melts 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.
On Mars’ dune fields, 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 of the sand below. As the bottom layer of the ice melts it traps the resulting CO2 between the sand and the ice above, building pressure.
When the ice inevitably cracks, it releases the gas in geyser-like blasts that also carry grains of sand, which is what you can see as the dark streaks and patches in the CaSSIS image.
The image also captures the merging of barchan dunes (on the right) into barchanoid ridges (on the left).
As we know, Mars has sand and that sand is formed into dunes by the wind, much the same way it is on Earth. The crescent, or U-shaped, dunes are called barchan dunes, and they are formed when the sandy ground is relatively flat and there is a fairly constant wind source from one direction. The tips of the crescent show us which way the prevailing wind blows as the crescents always point downwind. These dunes are the most common type, and are found in every desert on Earth and all over Mars.
Barchanoid ridges are formed when barchan dunes merge, producing longer wavy-looking ridges that look like rippled ice cream. The image, however, isn't just aesthetically pleasing, it provides useful information to scientists studying how conditions on Mars shape its landscape.
“Dunes come in various characteristic shapes on Mars just as on Earth, providing clues about the prevailing wind direction. Monitoring them over time also gives us a natural laboratory to study how dunes evolve, and how sediments, in general, are transported around the planet,” ESA said in a statement accompanying the image.
“The transition from barchan to barchanoid dunes tells us that secondary winds also play a role in shaping the dune field.”
Springtime on Mars is now coming to an end in the Northern Hemisphere as the summer solstice (when Mars' north pole is at its maximum tilt towards the Sun) is due to take place on October 8. Then we can look forward to the low Sun and good lighting allowing for some spectacular images to be taken on Mars.
