Mars’ ice caps offer clues to ancient climates

As a first-year master’s student in the Department of Earth Sciences, Katherine Lutz was fascinated by satellite images of Mars that showed spiral shapes swirling across the planet’s polar ice caps.

Made up of alternating layers of ice and dusty deposits and measuring 400 to 1,000 meters deep, these spiral patterns are not visible anywhere on Earth.

“These features are amazing, but do we really know why they form or how they change over time?” asks Lutz, now a doctoral student at the Guarini School of Graduate and Advanced Studies and a National Science Foundation fellow in the lab of Professor Marisa Palucis, whose research interests include the evolution of planetary landscapes. “Why are they there? How can we use these features?”

Layers of the polar ice cap provide scientists with one of the best climate records on the Red Planet.

“Mars has undergone major climate changes, and we spend a lot of time as planetary scientists trying to understand this,” Palucis says. “The question of how much water flowed on its surface (and when) has been central to its exploration.”

Research in 2013 suggested that these “troughs” could be caused by katabatic winds, winds that start out moving fast, causing erosion, then quickly diminish and slow down, causing deposition. Therefore, one would expect the troughs to have asymmetrical walls as well as cloud formations hovering above them that correspond to katabatic wind activity.

Working with Palucis and Earth science professor Robert Hawley, Lutz analyzed a decade of new Mars images and data and found that while 80 percent of the troughs were indeed asymmetrical, about 20 percent were not. In fact, the troughs on the outer edges of the ice sheet formed a fairly uniform “V” shape, with the walls on each side measuring about the same height. What’s more, not all of the troughs were covered in clouds.

In an article published in the Journal of Geophysical Research: PlanetsResearchers believe these outer troughs are younger than those in the center of the polar ice sheet and are likely caused by severe erosion rather than a cycle of katabatic winds.

This could suggest, Lutz says, that 4 to 5 million years ago there was a change in the Martian climate that altered the planet’s water cycle, causing winds, clouds and ice to flow differently.

This would help explain why the troughs in the center of the ice sheet are different from those at the edges, Lutz explains: they formed at different times, under different climatic conditions.

This type of discovery is crucial in trying to determine whether Mars can support – or has ever supported – life.

“If we ever want to send humans to Mars, we need to understand the history of this water source,” Lutz says, referring to the ice layers in these spirals.

“Could we use it to extract drinking water? And if we ever want to find evidence of life there, we’re not going to be looking at the outer edges of the ice sheet, where there’s a lot of erosion, where water doesn’t enter the system, and where there’s little warming.”

Lutz is quick to point out that these ice sheets are just traces of the climate of modern Mars. More modeling will be needed to better understand the history and function of these unique spirals, with the ultimate goal of sending a physical rover to Mars to “get more concrete information” about these troughs.