Â鶹ÒùÔº

On the slopes of Martian mountains and craters clings what appears to be flowing honey, coated in dust and frozen in time. In reality, these features are incredibly slow-moving glaciers, and their contents were once thought to be mostly rock enveloped in some ice.

Work over the last 20 years has demonstrated that at least some of these glaciers are mostly pure ice with only a thin cover of rock and dust, but according to a new published in Icarus, glaciers all over the planet actually contain more than 80% water ice, a significant finding. Ultimately, this means that Mars's glacial ice deposits are nearly pure across the globe, providing a clearer understanding of Mars' climate history and a possible resource for future utilization.

The paper was led by Yuval Steinberg, a recent graduate of the Weizmann Institute of Science, based in Israel. The two co-authors, Oded Aharonson and Isaac Smith, are senior scientists at the Planetary Science Institute, based in Tucson, with faculty appointments at the Weizmann Institute of Science and York University, respectively.

"This study highlights how NASA programs are advancing science not just within the United States, but also reaching students around the world," Aharonson said.

Peering under the dust-covered veil

While reading up on past research, the team quickly realized that when it comes to analyzing debris-covered glaciers, it's the Wild West.

"Different techniques had been applied by researchers to various sites, and the results could not be easily compared," said Smith. "One of the sites in our study had never been studied, and at two of the five sites we used, only partial analysis had been completed previously."

So, the team decided to standardize how these debris-covered glaciers are analyzed. They specifically measured their dielectric property (a measure of how quickly radar waves move through a material) and their loss tangent (a measure of how quickly energy dissipates from the radar wave into a material). From these, researchers can infer the ratio of rock to ice within a glacier. This cannot be done from visual observation of the glaciers that have dust and rock-covered surfaces.

They also identified another area on Mars where SHARAD, short for the SHAllow RADar instrument onboard the Mars Reconnaissance Orbiter, could also do these analyses. This gave them a total of five sites spread across the red planet, enabling global comparison.

They were surprised to find that all glaciers, even in opposite hemispheres, have nearly the same properties.

"This is important because it tells us that the formation and preservation mechanisms are probably the same everywhere," Smith said.

"From that, we can conclude that Mars experienced either one widespread glaciation or multiple glaciations that had similar properties. And, by bringing together these sites and techniques for the first time, we were able to unify our understanding of these types of glaciers."

Knowing the minimum purity of these glaciers benefits scientific understanding of the processes that form and preserve them. Additionally, it helps when planning for future human exploration of Mars, when using local resources, such as water, becomes mission-critical.

Next, the team will seek out additional glaciers to add their global comparison and solidify their understanding of these dust-covered mysteries.