While Mars may be a dessicated place where water no longer flows, the planet still has glaciers slowly moving across its surface. Previously, it was thought that Martian glaciers were pure ice with a thin cover of rock and dust. But after 20 years of exhaustive research, scientists have concluded that glaciers all over the planet contain more than 80% water ice, meaning they are nearly pure. These findings could alter our understanding of Mars’ climate history and have significant implications for future crewed missions dependent on in-situ resource utilization (ISRU).
Yuval Steinberg, a recent graduate of the Weizmann Institute of Science, led the research team responsible for these findings. He was joined by Oded Aharonson and Isaac Smith, two senior scientists at the Planetary Science Institute (PSI) with faculty appointments at the Weizmann Institute of Science and York University, respectively. The paper detailing their findings, “Physical properties of subsurface water ice deposits in Mars’s Mid-Latitudes from the shallow radar,” recently appeared in the journal Icarus.
The team’s study focused on Lobate Debris Aprons (LDAs), ice-rich landforms found on slopes of massifs, primarily in the mid-latitudes on Mars. Previously, researchers believed that these glaciers were either “rock glaciers” with a water ice content of 30% or composed of near-pure water ice beneath a layer of debris. The team was inspired by past research, which revealed that the study of ice formations on Mars has been somewhat irregular. To address this, the team sought to develop a standardized method for analyzing glaciers based on two key factors.
An artist’s impression of the Mars Reconnaissance Orbiter using its Mars Climate Sounder instrument.Credit: NASA/JPL-CalTech
These included how quickly radar waves pass through them (their dielectric properties) and how quickly energy from radar waves dissipates into them (their loss tangent). Using this method, the team selected five LDAs on Mars that were studied by the SHAllow RADar (SHARAD) instrument aboard the Mars Reconnaissance Orbiter (MRO). This allowed them to draw comparisons between glaciers located all across the planet, which revealed that all had virtually identical properties. As Smith explained in a PSI press release:
Different techniques had been applied by researchers to various sites, and the results could not be easily compared. 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. This is important because it tells us that the formation and preservation mechanisms are probably the same everywhere. 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.
Using this method, researchers can infer the ratio of rock to ice within, which cannot be done using visual observations of dust and rock-covered glaciers alone. Understanding the minimum purity of Martian glaciers will lead to a better understanding of the processes that form and preserve them, and will help when it comes time to plan for crewed missions. Per NASA’s mission architecture, landing site selection will need to account for the availability of essential resources, such as water ice. Aside from providing crews with a local source of drinking water, this ice can be fashioned into oxygen gas and rocket propellant.
“This study highlights how NASA programs are advancing science not just within the United States, but also reaching students around the world,” said Aharonson. For their next step, the team will look for additional glaciers to conduct more global comparisons, which will further augment our understanding of these debris-covered icy masses.
Further Reading: PSI, Icarus