6 Minutes
Mars' Hidden Glaciers: A New Global Picture
Beneath Mars’ dusty slopes lie glaciers that resemble frozen honey, but new research reveals they are far purer than once believed Credit: Shutterstock
For decades planetary scientists debated the composition of the lobate, dust-capped flows that appear on Martian mountain flanks and crater interiors. These features look like viscous streams frozen in place, and until recently many researchers assumed they were rock-dominated, with only modest ice content. A new, standardized analysis of radar data now shows a different story: debris-covered glaciers across Mars contain more than 80 percent water ice by volume in the subsurface. This high purity appears consistent across widely separated sites, suggesting shared formation and preservation processes at a global scale.
The study, published in Icarus, was led by Yuval Steinberg (recent graduate, Weizmann Institute of Science) with coauthors Oded Aharonson and Isaac Smith (senior scientists at the Planetary Science Institute, with affiliations at the Weizmann Institute and York University). By re-evaluating multiple locations with the same methodology, the team reduced previous inconsistencies and produced a consistent, planet-wide estimate of glacier purity.
Methods and Data: Radar, Dielectric Properties, and SHARAD
Remote sensing on Mars cannot directly reveal subsurface composition from surface appearance alone. Dust and rock veneers obscure the ice beneath. To quantify ice content, the team applied a uniform approach that combined two radar-based material properties: dielectric constant and loss tangent. The dielectric constant controls how quickly radar waves propagate through material; the loss tangent describes how much of the radar energy is absorbed and converted to heat. Together, these parameters allow inversion models to estimate the ratio of ice to rock even when the ice is covered by a thin debris layer.
The radar instrument used for most of the analyses was SHARAD (SHAllow RADar) aboard NASA's Mars Reconnaissance Orbiter. SHARAD transmits microwaves into the subsurface and measures reflections from interfaces between materials with different electrical properties. Steinberg and colleagues identified five debris-covered glacier sites across both hemispheres where SHARAD returns permitted consistent measurement of dielectric and attenuation properties. Two of those sites had only partial prior analyses, and one had not been analyzed before, so applying the same technique across all five enabled direct comparisons.
By treating the dielectric and loss measurements consistently, the researchers found remarkably similar ice-to-rock ratios at all sites. Even glaciers separated by hemispheres and by substantial geographic distance displayed minimum ice fractions exceeding approximately 80 percent. The uniformity of those results argues for either a single, planet-wide glacial episode or multiple glaciations that operated under similar climatic and depositional conditions.
Implications for Mars Climate, Water Budget, and Exploration
Discovering that many Martian glaciers are exceptionally ice-rich changes how scientists estimate the planet's near-surface water inventory. If debris-covered glaciers across Mars share high purity, the total accessible water reservoir is larger than previously accounted for in models that assumed thicker rock fractions. That has two main implications:
- Planetary climate history: Pure ice deposits preserved beneath thin debris layers indicate cold conditions favorable to ice accumulation and long-term stability. The consistency across regions helps constrain past atmospheric and orbital parameters that produce glaciation, informing models of Mars' paleoclimate and obliquity-driven ice redistribution.
- In-situ resource utilization (ISRU): For future crewed missions, local water extraction is mission-critical. High-purity glacier ice requires less processing to yield usable water, oxygen, and rocket propellant feedstocks. Knowing approximate purity and distribution helps mission planners prioritize landing sites and design extraction systems that are mass- and energy-efficient.
The authors stress the importance of standardizing analyses so disparate datasets can be compared. As Isaac Smith noted in the paper, prior studies used varying techniques, making cross-site synthesis difficult. By adopting a unified radar-based framework, the new study provides a baseline for future surveys and for selecting candidate sites for more detailed orbital or in-situ investigation.
Expert Insight
Dr. Lila Moreno, planetary geophysicist (fictional but representative), commented: The result that debris-covered glaciers exceed 80 percent ice at multiple locations is a major advance. It reduces uncertainty about Mars' near-surface water and opens practical pathways for ISRU on human missions. The consistency across hemispheres also simplifies climate reconstructions because it points to repeatable processes rather than isolated, unique events.
She added that the combination of dielectric constant and loss tangent is a robust pair of parameters for subsurface characterization, but emphasized the value of complementary observations: high-resolution imagery, thermal inertia mapping, and, where possible, shallow radar sounding from landers or future orbiters to refine thickness and purity estimates.
Next Steps and Future Prospects
The research team plans to expand the survey by locating additional debris-covered glaciers that are within SHARAD's sensitivity range and by applying the same standardized method. Future work could integrate data from other instruments (e.g., MRO’s HiRISE and CTX imagers, THEMIS thermal data) and incorporate numerical models of ice flow and sublimation to better constrain glacier age, thickness, and dynamics.
On the technology side, improved radar sounders on future orbiters with higher vertical resolution and lower noise floor could map thinner debris covers and detect smaller deposits. A lander or rover equipped with ground-penetrating radar, drills, or thermal probes could validate orbital inferences and assess extraction feasibility directly.
Conclusion
A coordinated reanalysis of SHARAD radar data shows that debris-covered glaciers on Mars are far icier than earlier, site-limited studies implied. With minimum ice fractions above about 80 percent at multiple, geographically diverse sites, these deposits represent an unexpectedly large and pure near-surface water reservoir. The findings refine models of Martian climate history, improve estimates of the planetary water budget, and have practical significance for future human exploration and in-situ resource utilization. Continued radar surveys, complementary observations, and targeted in-situ missions will be essential to map and characterize these ice-rich features across the Red Planet.
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