The surface of Mars, now a cold, dry, and inhospitable world, provides a stark contrast to the planet’s past. Once, this red planet might have been far more Earth-like: warmer, wetter, and crisscrossed with rivers, lakes, and glaciers. Today, the majority of the planet’s water remains locked away in its polar ice caps, beneath its surface as permafrost, or within subsurface glaciers. However, the annual cycle of melting and freezing ice at Mars’ poles still has a notable impact on the planet’s environment, offering tantalizing clues to its glacial past.
In recent research, a team of scientists from the Planetary Science Institute (PSI) conducted a detailed study on a region of Mars known as Arabia Terra, which contains a mid-sized crater and a neighboring depression called the Heart Lake System. Their findings, presented at the 2025 Lunar and Planetary Science Conference in Woodlands, Texas, suggest that the region’s features were shaped by subglacial melting and glacial retreat. Specifically, the scientists propose that a receding glacier in the area created the depression, leaving behind a complex system of shallow channels, a proglacial lake, and smaller glacial deposits, shedding light on the role of glaciation in Mars’ ancient climate.
The Study of Glacial Features on Mars
Glaciers on Mars have been a subject of study since the Viking missions of the 1970s, and much of our understanding of them comes from their distinctive surface features. These glaciers, often covered in debris, display characteristic shapes such as lobed structures, deformations, crevasses, and pits. In addition to these, terminal moraines—ridge-like accumulations of glacial debris—have been found at the edges of these glaciers, suggesting that ice loss has occurred over time. These observations, along with the physical features of glacial activity, have been fundamental in piecing together Mars’ dynamic past.
However, the nature of these glaciers remains a topic of debate. Many scientists have long assumed that Mars’ glaciers were “cold-based,” meaning that they did not experience melting at their bases. This would suggest that no significant meltwater was involved, and consequently, no channels or eskers (winding ridges formed by glacial meltwater) were expected to appear near them. These cold-based glaciers were thought to have formed hundreds of millions of years ago, during a time when Mars was too cold for significant melting to occur.
In more recent studies, however, evidence has emerged suggesting that some regions on Mars might have experienced “wet-based” glaciation, where subglacial melting did take place. This possibility has spurred further exploration of Mars’ glacial features, especially those thought to be formed more recently. Among the key questions that remain are whether these features were indeed shaped by melting ice, and if so, what does that say about Mars’ climate during those periods?
Mapping Mars’ Glacial Landscape
In an effort to address these questions, Dan Berman and Dr. Rebecca M. E. Williams, senior scientists at the Planetary Science Institute, used state-of-the-art Geographic Information System (GIS) technology to map out the glacial features in and around a 48-kilometer-wide crater located in northern Arabia Terra. This area, which is home to the Heart Lake System, has long been suspected to contain evidence of ancient glaciation, as well as signs of water activity. Their team used Digital Terrain Models (DTMs) to analyze detailed topographic data collected by the Mars Reconnaissance Orbiter (MRO), which allowed them to construct high-resolution maps of the region’s surface features.
The crater they studied had been previously identified as a potential paleolake, and it showed multiple indicators of water-based glacial activity. The scientists found meltwater channels and hanging valleys on terraces along the crater’s inner walls, which bear a striking resemblance to post-glacial terrains on Earth, particularly those found in alpine valleys. These valleys and ridges suggested the presence of water at some point in Mars’ past, and the scientists hypothesized that they had been shaped by the action of ice. The region also contained incised valleys along the crater’s inner and outer walls, as well as the ejecta blanket—a deposit of material thrown out during the impact that created the crater. These valleys, along with the alluvial fans (fan-shaped deposits of material transported by water), provided further evidence that water once existed in the region.
In addition to these features, Berman and Williams identified sinuous ridges extending from beneath the alluvial fans, which could be interpreted as inverted channels, a typical feature left behind when flowing water or ice melts and deposits material in a channel. These ridges, however, could also be eskers, winding ridges formed by the movement of meltwater beneath a glacier. The presence of both types of features suggests that subglacial melting and subsequent water flow played a significant role in shaping the region.
Implications of Subglacial Melting and Glacial Retreat
The study conducted by Berman and Williams provides compelling evidence that subglacial melting and glacier retreat were pivotal in forming the Heart Lake System and the surrounding features in northern Arabia Terra. The evidence suggests that these glaciers were “wet-based,” meaning that their bases were warm enough for melting to occur, allowing water to flow beneath the ice. This meltwater would have contributed to the formation of channels, lakes, and other features that are typically associated with glacial activity on Earth.
The findings also challenge previous assumptions about Mars’ climate during the early Amazonian Period, which began around 2.9 billion years ago. The presence of wet-based glaciers and meltwater features implies that the climate in this period may have been warmer than scientists had previously believed. This is a significant discovery because it could provide valuable insights into the conditions that allowed liquid water to exist on the surface of Mars for extended periods in the past. It also raises the question of when and why Mars lost its water, a mystery that remains central to understanding the planet’s geological evolution and its potential for past habitability.
The study also contributes to the growing body of evidence that Mars may have had a more dynamic climate than scientists initially thought, with periods of warming and cooling over its history. These fluctuations in climate could have had a profound impact on the planet’s ability to support life. By better understanding the conditions that allowed for glaciation and subglacial melting on Mars, researchers may uncover new clues about the planet’s ability to sustain liquid water—and perhaps even microbial life—during certain periods in its history.
Future Exploration and the Search for Evidence of Ancient Life
The findings of Berman and Williams open exciting possibilities for future exploration of Mars. Robotic missions, and potentially even crewed missions, could visit the Heart Lake System and other regions with similar glacial features to directly investigate the origin of these formations. By studying the composition of the soil, ice, and rock in these areas, scientists hope to determine whether subglacial melting played a role in shaping Mars’ surface and whether these processes could have supported the development of life on the planet.
One of the most promising aspects of this research is its potential to shed light on Mars’ history of water and its implications for habitability. If the Heart Lake System and other regions like it once harbored liquid water beneath glaciers, these locations could represent ancient environments where life may have existed. By focusing on these areas, scientists could be one step closer to answering the age-old question: Was Mars ever capable of supporting life?
Conclusion
The study of Martian glaciers and the processes that shaped the Heart Lake System provides a fascinating glimpse into the planet’s past and its potential for harboring life. The evidence of subglacial melting and glacial retreat offers new insights into Mars’ climate history and challenges our understanding of its geological evolution. As our exploration of Mars continues, research like this will be key to unraveling the mysteries of the Red Planet’s past and guiding future missions that may one day answer the ultimate question: Could life have once thrived on Mars? The search for answers continues, and each discovery brings us closer to understanding the enigmatic world that is our planetary neighbor.
Reference: Sub-Glacial Melting in Northern Arabia Terra? Evidence for Valley Glaciers, Meltwater Channels, and Proglacial Lakes. www.hou.usra.edu/meetings/lpsc2025/pdf/1530.pdf