Scientists have discovered that salt glaciers may exist on Mercury, the planet closest to the sun and the smallest world in the solar system. This discovery could show that even the most volatile conditions in the inner solar system can sometimes echo conditions seen on Earth.
The team’s findings complement recent discoveries that revealed Pluto had nitrogen glaciers. Because Pluto exists on the other side of the solar system, both findings imply that glaciation extends from the solar system’s warmest regions, close to the sun, to its frigid outer limits.
Even more interesting, scientists at the Planetary Science Institute (PSI) believe that these saline glaciers could create conditions suitable for life, similar to those in some extreme environments on Earth where microbial life flourishes. “Specific salt compounds on Earth create habitable niches, even in the harshest environments where they are found, such as in the arid Atacama Desert in Chile,” explains Alexis Rodriguez, lead author of the study and researcher at PSI . said in a statement. “This line of thinking leads us to consider the possibility of subterranean areas on Mercury that might be more hospitable than its hard surface.”
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Locations like those highlighted by the team are of critical importance because they identify volatility-rich exposures across the vastness of multiple planetary landscapes. They also suggest that the solar system might contain so-called “depth-dependent Goldilocks zones,” regions on planets and other bodies where life might survive not on the surface, but at specific depths that present exactly the right conditions.
“This groundbreaking discovery of Mercurian glaciers expands our understanding of environmental parameters that could support life, adding a vital dimension to our exploration of astrobiology also relevant to the potential habitability of Mercury-like exoplanets,” Rodriguez said.
Mercury may be richer in volatile substances than we thought
This research challenges the idea that Mercury lacks volatiles, chemical elements and easily vaporized compounds that were essential for the emergence of life on Earth.
This indicates that volatiles may be buried beneath the surface of the small planet in volatility-rich layers (VRLs). The team also has an idea of how these VRLs were exposed on Mercury’s surface.
“These Mercurian glaciers, distinct from those on Earth, originate from deeply buried VRLs exposed by asteroid impacts,” said research co-author and Planetary Science Institute (PSI) scientist Bryan Travis. “Our models strongly argue that salt flows likely produced these glaciers and that after they were established, they retained volatiles for more than a billion years.”
The team believes that Mercury’s glaciers are arranged in a complex configuration with troughs that form young “sublimation pits” – sublimation being the process by which a solid instantly transforms into a gas without passing through a liquid phase.
“These troughs have depths that represent a significant portion of the glacier’s overall thickness, indicating that they largely retain a composition rich in volatile substances,” said Deborah Domingue, a scientist and member of the team of the PSI. “These hollows are visibly absent from the floors and walls of the surrounding craters.”
Domingue added that this observation, by showing that asteroid impacts revealed VRLs, provides a coherent solution to a previously unexplained phenomenon: the apparent correlation between hollows and crater interiors. The team’s research suggests that groups of hollows in impact craters could originate from areas of VRL exposure caused by space rock impacts; As impacts expose the volatiles, they sublimate into gas, leaving the hollows behind.
Salty chaos on Mercury
Rodriguez and his colleagues examined the boreal chaos to determine the connection between Mercury’s glaciers and its chaotic terrain and infer what might be responsible for the formation of VRLs.
This area is located in Mercury’s north polar region and is marked by complex decay patterns that appear large enough to have obliterated entire populations of craters, some dating back about 4 billion years. Beneath this collapsed layer of Borealis Chaos lies an even older crater surface that has already been identified through gravity studies.
“The juxtaposition of the fragmented upper crust, now forming chaotic terrain, on this ancient surface revealed by gravity suggests that the VRLs were placed atop an already solidified landscape,” Rodriguez said. “These findings challenge dominant theories of VRL formation, traditionally focused on mantle differentiation processes, in which minerals separate into different layers within the planet’s interior. Instead, the evidence suggests a large-scale structure, possibly resulting from the collapse of an ephemeral, warm primordial atmosphere early in Mercury’s history.”
The PSI team believes that this atmospheric collapse could have occurred mainly during prolonged nighttime periods on Mercury, when the planet’s surface was not exposed to the intense heat of the sun, causing temperatures to drop by around 800 degrees Fahrenheit (430 degrees Celsius), or a temperature hot enough to melt lead – minus 290 degrees Fahrenheit (minus 180 degrees Celsius).
Salt-dominated VRLs on Mercury may also have grown considerably due to underwater deposition, an idea that also represents a significant departure from previous theories about the early geology of the planet closest to the sun .
“In this scenario, water released by volcanic degassing may have temporarily created pools or shallow seas of liquid or supercritical water, such as dense, very salty vapor, allowing salt deposits to settle,” he said. said team member and PSI researcher Jeffrey S. Kargel. “The rapid loss of water to space and the trapping of water in the hydrated minerals of the crust would have left behind a layer dominated by salt and clay minerals, which gradually accumulated into deposits thick.”
The team’s research is published in the Journal of Planetary Sciences.