NASA / JPL / USGS
A new study suggests the hypothesis using the glaciers on Deceção Island in Antarctica as analogues for possible glaciers beneath the Hecates Tholus volcano.
When we think of ice on Mars, we usually think of the poles, where we can see it through land-based probes and even telescopes. But the poles are difficult to access, even more so due to restrictions on exploration in this region due to potential biological contamination.
Scientists have long hoped to find water closer to the equator, making it more accessible to human explorers. There are parts of the mid-latitudes of Mars that appear to be covered glaciers through thick layers of dust and rock. So, do these formations really contain massive water reserves near the place where humans might first set foot on the Red Planet? According to a new report by de Pablo and his co-authors, recently published in the journal Icarus, it’s possible so.
The key may lie on a small volcanic island in Antarctica. Known as Deception Island, it is a volcano that covered some huge glaciers around it with ash and dust from a series of eruptions in the 1960s and 1970s. The authors believe they have found a volcano on Mars with a similar history, known as Hecates Tholus.
Hecates Tholus is an ancient shield volcano on Mars that has many of the same characteristics as the Deception Island volcano. And since we know there is ice deposited beneath the debris in Antarctica, this implies that similar features may be present. beneath the debris surrounding Hecates Tholus.
There are several features on Mars that strongly suggest the presence of glacial ice, rather than just loose rock or even cemented rock. with a small amount of ice. Firstly, there are the cracks. Any explorer will tell you how absurdly dangerous these features are on Earth, but the main feature of the crevasses on Deception Island is that they are visible from space, particularly near what is known as the glacier’s “front walls” – the steep, almost vertical cliff that presents itself as the upper end of a glacier. Similar features are visible from space on Hecates Tholus, and such sharp and visible fractures would not be noticeable if there were only underlying rock. Specifically, these cracks indicate that a solid ice core is still moving under the surface of volcano debris.
Another crucial piece of evidence is the presence of bergschrunds. These are distinct, deep crevasses that form at the top of a glacier. All bergschrunds are technically a type of crack, although they are much larger and created by a very specific process compared to typical examples. This process is the separation of moving ice from stagnant ice. Some examples of bergschrunds near Hecates Tholus are up to 600 meters long and are a clear indication that, at least at some point, there was active ice movement.
A final point of evidence is the bulldozer effect – or more specifically, the presence of “thrust moraines” at the bottom of the valleys of both Deceção Island and Hecates Tholus. When they move, glaciers act like tractors, pushing huge rocks in front of them and leaving rugged terrain behind. Shapes similar to those observed on Deceção Island are again visible around Hecates Tholus, indicating that, at some point, there was an active glacier in the area.
So, if these glaciers really exist, how did they survive for millions of years without evaporating? The authors propose a two-step process. First, when the cracks formed, some of the water sublimated, but these holes were then covered in dust, protecting the newly exposed water from further sublimation. Eventually, this resulted in the shallow “depressions” that are what we see on Mars, rather than actual rifts.
An obvious question for those who closely follow the exploration of Mars is: why hasn’t SHARAD detected anything there? If there is an underground glacier at the equator, the Mars Reconnaissance Orbiter’s ground-penetrating radar will certainly would be able to capture a signal from the same. After all, we have repeatedly reported this phenomenon in other regions of Mars (and have occasionally had to “update” these findings). SHARAD’s radar physics don’t work well on the steep slopes of volcanoes, making it difficult to get a clear image of whatever lies beneath the dust and debris. To really understand this better, we will need samples collected from the surface, whether by robots or humans.
But there is another implication implicit in the article. If Mars really has huge glaciers hidden near Hecates Tholus, there may be many others hidden close to other gigantic volcanoes too. Article IX of the 1967 Outer Space Treaty requires that the exploration of other bodies in the Solar System avoids “harmful contamination” of celestial bodies. Many people interpreted this clause as requiring explorers to avoid the Martian poles, where there is evidence of too much water. If there is water all over Mars, buried beneath volcanic debris, does that mean those areas are off-limits to explorers as well?
Only time will tell the answer – and we may never know for sure if there is water around these volcanoes unless we send explorers there – there is a limit to what we can do remotely. There are some mission proposals that could resolve the debate, such as FlyRADAR, but for now we will have to wait for definitive confirmation about whether Martian volcanoes are covered by glaciers — and maybe spy a Deceptive volcano nearby, in the meantime.
