Bizarre features on Mars are caused by carbon dioxide geysers

Though it’s a cold, dead planet, Mars still has its own natural beauty about it. This image shows us something we’ll never see on Earth.

Mars has only a thin, tenuous atmosphere, and most of it (95%) is carbon dioxide. When Martian winter arrives, CO₂ freezes and forms a thick coating on the ground in the polar regions. It lies there dormant for months.

As spring approaches, temperatures gradually warm. Sunlight passes through the translucent frozen layer of CO₂, warming the ground beneath it.

The warming ground sublimates frozen CO₂ into vapor that accumulates under the solid CO₂. Eventually, the gas escapes through weak spots in the ice. It can erupt into geysers that spread darker material out onto the frozen surface.

The HiRISE camera on NASA’s Mars Reconnaissance Orbiter captured the image above of these geysers on Mars in October 2018. It has also captured other images of Martian CO₂ geysers.

Some of Mars’s CO₂ geysers erupt and create dark spots as large as 1 km across. They are fueled by considerable power and can erupt at speeds up to 160 km/h.

Sometimes the eruptions create dark regions under the ice which look like spiders.

Scientists are calling these features araneiform terrain or spider terrain. They are found in clusters that give the surface a wrinkled appearance. NASA scientists recreated these patterns in lab tests to understand the processes behind their formation. “The spiders are strange, beautiful geologic features in their own right,” said Lauren McKeown of NASA’s Jet Propulsion Laboratory in Southern California.

The process that explains how the CO₂ cycle creates these features is called the Keiffer model. Hugh Keiffer was with the US Geological Survey when he and his colleagues published a paper explaining the model in 2006 in Nature titled “CO₂ jets formed by sublimation beneath translucent slab ice in Mars’s seasonal south polar ice cap.”

“We propose that the seasonal ice cap forms an impermeable, translucent slab of CO₂ ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO₂ vents that erupt sand-sized grains in jets to form the spots and erode the channels,” Keiffer and his co-authors wrote in their paper.

Maybe humans are biased, but there’s nothing as beautiful and splendorous as Earth. Generations of poets have acclaimed its beauty to the point where it borders on the spiritual. However, when it comes to CO₂ geysers and the natural patterns they create, Mars has something that Earth doesn’t.

“These processes are unlike any observed on Earth,” the authors of the 2006 paper stated.