Everyone knows that there are volcanoes on Mars. Everyone knows that there are glaciers on Mars. But now scientists suggest that, at least on some volcanoes on the red planet, glaciers may be hidden under a layer of ash.

Hecates Tholus.
Source: Wikipedia

Prevalence of glaciers on Mars

When we think of ice on Mars, we usually mean the poles, where it can be seen with probes and even ground-based telescopes. But the poles are difficult to reach, and even more so because of restrictions on research there due to potential biological contamination. Scientists had long hoped to find water closer to the equator, which would make it more accessible to human explorers. There are parts of Mars’ mid-latitudes that look like glaciers covered with thick layers of dust and rocks.

So, do these formations really conceal large reserves of water near the place where humans may first set foot on the Red Planet? Perhaps, yes, according to a new article by M.A. de Pablo and his co-authors, recently published in the journal Icarus.

The key may be a small volcanic peninsula in Antarctica. Known as Deception Island, this volcano covered part of the surrounding huge glaciers with ash and dust from a series of eruptions in the 1960s and 1970s. The authors believe they have found a volcano with a similar history on Mars, known as Hecates Tholus. 

Hecates Tholus. is an ancient shield volcano on Mars that shares many of the same features as the volcano on Deception Island. And since we know that there is ice beneath the debris in Antarctica, this could mean that similar features may be found beneath the debris around Hecates Tholus.

Evidence of a glacier near Hecates Tholus

There is some compelling evidence on Mars that suggests the presence of glacial ice, rather than just loose rock or even rock cemented together with a small amount of ice. First and foremost, there are the crevasses. Any researcher will tell you how absurdly dangerous these features are on Earth, but the key characteristic on Deception Island is their visibility from space, especially near the so-called “headwalls” of the glacier — steep, almost vertical cliffs at the upper end of the glacier.

Such features are visible from space on Hecates Tholus, and such clear, visible fractures would not be noticeable if there were simply rock beneath them. In particular, these fractures mean that the solid ice core is still moving beneath the surface of volcanic debris.

Another direct piece of evidence is the presence of bergschrunds. These are distinct, deep cracks that form at the top of a glacier. Technically, all bergschrunds are a type of crack, although they are significantly larger and are formed by a very specific process compared to ordinary cracks. This process consists of separating movable ice from frozen ice. Some examples of bergschrunds near Hecates Tholus reach lengths of 600 m and are clear evidence that, at least at a certain point in time, there was active ice movement.

The final proof is the bulldozer effect, or, more precisely, the presence of “push moraines” at the bottom of the valleys of both Deception Island and Hecates Tholus. When glaciers move, they act like bulldozers, pushing huge rocks in front of them and leaving hilly terrain behind. Similar formations, such as those seen on Deception Island, are again visible around the volcano, indicating that a glacier once actively existed in this area.

Martian volcanoes could be hiding massive glaciers under a blanket of ash

Overview and context of Hecates Tholus, Mars (left) and the terrestrial analog, Deception Island (right).

Credit: Icarus (2026).

DOI: 10.1016/j.icarus.2026.116966

How to find hidden glaciers?

So if these glaciers really exist, how have they managed to survive for millions of years without evaporating? The authors propose a two-stage process. Initially, when cracks formed, some of the water actually sublimated, but these holes were then covered with dust, protecting the newly exposed water from further sublimation. Ultimately, this led to the formation of shallow “troughs,” which we actually see on Mars instead of real cracks.

One obvious question for people who closely follow Mars exploration is: why didn’t SHARAD see anything there? If there is a subsurface glacier at the equator, then the ground-penetrating radar on the Mars Reconnaissance Orbiter would undoubtedly be able to detect a signal from it. The physics of SHARAD radar does not work well on the steep slopes of volcanoes, making it difficult to obtain a clear image of what lies beneath the dust and debris. In order to truly understand the situation better, we will need samples from the surface, both from robots and from humans.

Fraser talks about the restriction of exploration missions to the Martian South Pole.

Avoid contamination

If there really are huge glaciers on Mars hidden beneath the dome of Hecate, there may be many others hidden beneath other massive volcanoes. Article IX of the 1967 Outer Space Treaty requires that exploration of other bodies in the Solar System be conducted in such a way as to avoid “harmful contamination” of celestial bodies. Many interpreted this article as a requirement for researchers to avoid the Martian poles, where there is evidence of large amounts of water. If it turns out that there is water all over Mars, hidden under volcanic debris, does that mean that these areas are now also off-limits to researchers?

Only time will tell the answer to this question — we may never know if there is water around these volcanoes unless we send researchers there — everything we can do remotely is limited. There are some proposals for missions that could resolve this question, such as FlyRADAR, but we will have to wait for the final word on whether Martian volcanoes are covered by glaciers — and perhaps look at the deceptive volcano on our own planet in the meantime.