When glaciers roamed Mars

The surface of Mars is known for being an extremely cold, desiccated, and irradiated place. But as its many surface features attest, the red planet was once a warmer, wetter place with flowing water and glaciers. Today, most of the remaining water on the surface is largely confined to its polar regions in the form of ice caps, permafrost, and subsurface glaciers. Nevertheless, the seasonal melting and freezing of this ice still impacts the Martian environment and offers clues about glacial activity in the past.

In a recent paper, a team of scientists from the Planetary Science Institute (PSI) examined subglacial melting in and around a mid-sized crater in the northern Arabia Terra region and the neighboring depression—the Heart Lake System.

Based on multiple lines of evidence, they propose that a receding regional glacier created the depression. Similarly, they argue that subglacial melting formed the shallow channels in the region, leaving behind a proglacial lake with smaller glacial deposits within the crater, leading to subsequent meltwater and lake formation.

The paper was the subject of a presentation delivered at the 2025 Lunar and Planetary Science Conference, which took place from March 10–14, 2025, in Woodlands, Texas. Its authors are Dan Berman and Dr. Rebecca M. E. Williams, two PSI Senior Scientists. Whereas Berman is a member of multiple studies with the NASA Mars Data Analysis Program and a team member of the Mars Reconnaissance Orbiter (MRO) mission, Williams has been a member of multiple mission teams, including the Perseverance and Curiosity rovers, Mars Odyssey, Mars, MRO, and Mars Global Surveyor (MGS).

As they indicate in their paper, features that form in the presence of glaciers have been studied on Mars since the 1970s, beginning with the Viking missions. These features have been interpreted as debris-covered glaciers due to their shape, which consists of lobe-like features, signs of deformation, and surface textures such as linear structures, crevasses, and pits. Terminal moraines, ridge-like accumulations of glacial debris, have also been observed beyond them, indicating that they experience ice loss.

As Berman explained to Universe Today via email: “These glaciers are thought to be “cold-based” meaning that there is no melting at their bases that would facilitate sliding because signs of melting, such as meltwater channels and eskers, are rarely observed in their vicinity. These features are thought to have formed several hundred million years ago, suggesting that conditions were too cold for ice to melt at that time. More recent observations have pointed to several regions on Mars with potential eskers [winding ridges of sand and gravel formed by glacial meltwater] emanating from beyond viscous flow features, but the origin of these ridges is still under debate.”

These last features and hydrologic models indicate that wet-based glaciation is possible, though evidence of sub-glacial melting has been limited. To address this, Berman and Williams mapped these features using Geographic Information System (GIS) technology. They also constructed Digital Terrain Models (DTM) based on the Global CTX and images taken by the Context Camera (CTX) and the High-Resolution Imaging Science Experiment (HiRISE) on NASA’s Mars Reconnaissance Orbiter (MRO).

Their study focused on the region in and around a 48 km-diameter (30 mi) crater in northern Arabia Terra and the neighboring Heart Lake System. As Berman explained, this crater was previously identified as a potential paleolake, with multiple features that are indicative of wet-based sub-glacial melting.

“These include potential meltwater channels and hanging valleys on terraces along the crater wall interior that resemble post-glacial terrains in alpine valleys. The crater has incised valleys on the inner and outer walls, as well as on the ejecta blanket, with alluvial fans deposited at their termini along the crater floor, suggesting the former presence of a body of water within the crater. Sinuous ridges extend from beneath these fans, which could be interpreted as inverted channels, but also could be eskers due to their sharp crests and gradients. The neighboring depression also shows evidence of valleys debauching into it and alluvial fans and ridges.”

Using GIS and their DTMs, Berman and Williams analyzed the topography and slopes of these features. Their results suggested that portions of the valleys and ridges may have gone uphill, suggesting they may be glacial in origin. These findings indicate that Mars may have been warmer than previously thought during the early Amazonian Period, Mars’ current geological era, which began 2.9 billion years ago. This could have significant implications for our understanding of Mars’s geological evolution and help address the unresolved question of when Mars lost its water.

This presents opportunities for future exploration, where robotic and crewed missions could observe these features to determine whether they were formed by melting ice.