University of Calgary

Geographer adds his expertise to NASA research into Mars water question

UToday HomeJune 18, 2013

By Heath McCoy

Christopher Hugenholtz is an assistant professor in the Department of Geography, Faculty of Arts.Christopher Hugenholtz is an assistant professor in the Department of Geography, Faculty of Arts.University of Calgary geographer Christopher Hugenholtz has lent his expertise to a NASA research project which challenges the widely circulated theory that water exists on Mars.

The water theory gained momentum in academic circles and the media in the past decade, based partly on the evidence of eroded channels and linear gullies found on the slopes of Martian sand dunes, as seen in satellite imagery captured by the Mars Reconnaissance Orbiter.

It has been speculated that these gullies had to have been formed by running water. This notion excites the public imagination because the existence of water on Mars has huge implications when considering the possibility of life on the red planet.

But a recent study led by NASA’s Jet Propulsion Laboratory, with assistance by Hugenholtz and other researchers, offers a new explanation for the Martian gullies. The report, published online by the journal Icarus, indicates that the grooves were more likely formed by blocks of carbon dioxide, or dry ice.

How Hugenholtz got involved in research

How did an Alberta geographer wind up working on a NASA study on the surface of Mars?

“My background is geomorphology,” explains Hugenholtz. “It’s a discipline that focuses on land forms and processes. When I was looking at the images of Mars online and reading all these reports about water on Mars, I felt that these theories just didn’t line up.”

In particular, Hugenholtz noticed that small pits existed at the bottom of the Martian gullies. “To me, this suggested water was not the cause for the gullies,” he says. “In my experience, studying similar features on Earth, gullies formed by running water almost always end with an apron of the sediment that was eroded as the gully was carved out.”

Images captured by the Mars Reconnaissance Orbiter reveal eroded gullies in Martian sand dunes. What caused them? Photo courtesy NASAImages captured by the Mars Reconnaissance Orbiter reveal eroded gullies in Martian sand dunes. What caused them? Photo courtesy NASAThe blocks of dry ice theory

Hugenholtz theorized that the gullies were formed by blocks of CO2 ice which, propelled by the releasing of gas, essentially floated down the slopes, sublimating at the bottom and forming the pit feature.

“I had this echoing in my mind,” says Hugenholtz, when in 2011 he attended a conference of the American Geophysical Union and sat down to a presentation by NASA’s Jet Propulsion Lab. “I felt my gut twist as I saw exactly what I envisioned,” he says.

In the presentation, satellite images showed blocks of CO2 ice in the gullies. Hugenholtz approached Serina Diniega, a planetary scientist at NASA and the lead researcher on the project.

“She realized that they needed somebody who works on the ground on Earth to help them understand this and we brought in physicists and other researchers to develop a good argument for our idea,” says Hugenholtz.

The study suggests that CO2 ice blocks are formed in the Martian winter when a blanket of carbon dioxide frost accumulates on the planet’s steep slopes. Over time the density of the frost layers increases until slabs of CO2 ice are formed. In the spring, the CO2 begins to sublimate, releasing gas which causes the blocks to break off and slide down the slopes.

“The debated question has been, could water exist on Mars today, running down the slopes and forming these features?” says Hugenholtz. “Our work adds more evidence to the contrary. I think this transforms the way a lot of people will think about Mars.”