Salt glaciers on Mercury’s surface open new horizons in astronomy

When we talk about any planet that may or may have life, Mercury seems to be completely out of the picture. Extremely hot from the Sun, from which it is only 46 million kilometers away, this small, dry and atmosphere-less planet is very far away indeed. Present the necessary conditions for the emergence of life.

At least on the surface. Because deep down things can be very different. This is what a new study published in the journal suggests Planetary Science Journal, New data that constrains our view of the zone considered habitable in planetary systems and significantly expands the field of possibilities in astronomy.

Salt glaciers are releasing volatile elements

Its distance from the Sun puts Mercury outside the habitable zone, which is between Venus and Mars for our solar system. In full sun with temperatures exceeding 400°C, there is no possibility of finding liquid water. However, we now know that some planets may offer favorable habitable conditions despite extremely hostile surface environments. The hidden oceans of the icy moons of Jupiter and Saturn are perfect examples. But apart from a massive iron core and a thin silicate mantle, Mercury doesn’t hide any oceans of liquid water. So, where might scientists find conditions potentially capable of supporting life?

Well, in the glaciers…of salt! While it was thought that Mercury’s crust was completely devoid of any volatile components, this certainty was broken by the passage of the Messenger probe between 2011 and 2015. Sulfur, chlorine, sodium and potassium were indeed detected on the planet’s surface. The volatile elements appear to emerge from the subsurface and suggest the presence of a “reservoir” hidden in the planet’s basement.

A more favorable environment for life in the subsoil of Mercury?

The new study also suggests that this layer, rich in unstable elements, may be much larger than previously thought. The results indeed suggest that emissions of volatile elements are greater in areas of very chaotic terrain, whose morphology is reminiscent of Martian glaciers. Analysis of these landmasses, particularly at the poles, shows that they are large salt reservoirs in which volatile elements were trapped at the time of formation. These distinctive glaciers, buried in Mercury’s subsoil for more than a billion years, would then have been exposed on the surface due to asteroid impacts.

This type of glacier has terrestrial analogues, including the dry saline deposits of the Atacama Desert in Chile. However, we know that such environments may represent favorable habitable conditions for extremophile organisms.

New Perspectives in Astronomy

Based on modeling, researchers suggest that these glaciers formed during the collapse of a short-lived and warm primordial atmosphere early in Mercury’s history, before the Late Great Bombardment episode. Water in the atmosphere, ejected by volcanic activity, may have condensed on the surface during the long, cold night periods that the planet experiences due to its slow rotation. This scenario therefore suggests the temporary presence of shallow and very salty seas about 4 billion years ago. After this, due to rapid evaporation and lack of water in space, huge reserves of salt would have formed within the earth’s crust.

A new geological story that could give new appeal to the search for extraterrestrial life on Mercury and its counterparts elsewhere in the Galaxy.