London: Scientists from the UK have been able to recreate extreme conditions found on icy moons in deep space and said the unstable behaviour of water revealed can help identify ancient signs of cryovolcanic activity across celestial bodies in the solar system.
In the near-zero pressure environment of space, water reacts very differently from how it does on Earth and simultaneously undergoes both boiling and freezing.
The icy moons are covered in an ice exterior with liquid oceans existing below the ice crust. Just as lava through volcanic activity reshapes the Earth’s surface, water reshapes icy moons through a process called cryovolcanism.
Researchers from the University of Sheffield, the Open University, and the Czech Academy of Sciences used a specially constructed low-pressure chamber to create the near-vacuum-like conditions found on Europa and Enceladus, both with frozen exteriors, to understand how the altered behaviour of water might be driving geologic change on the icy moons.
Europa is the icy moon that orbits Jupiter. Enceladus orbits Saturn.
The findings published in the journal Earth and Planetary Sciences Letters said the research team wanted to see if they could identify how effusive cryovolcanism happens by studying the behaviour of water in a near-vacuum environment, Sheffield University said in a release here on Wednesday.
Astronomers have seen evidence of giant jets of water vapour and water particles being vented or ejected into space by a volcano-like process known as explosive cryovolcanism. In effusive cryovolcanism, liquid is released as a flow on the surface of the icy moons, akin to a lava flow found on Earth. They said, evidence for such an activity is hard to detect.
The scientists used a low-pressure chamber, George the Large Dirty Mars Chamber, housed at the Open University. For the first time, scientists were able to run experiments with relatively large volumes of water and, through observation ports, filmed what was happening, the release said.
Lowered pressure inside the chamber led the water to bubble and boil; boiling created vapour which transported heat away from the water, and the water cooled, reaching its freezing point, and floating pieces of ice were formed, which continued to grow in size, with new ice forming around their edges.
Within a few minutes, most of the water was covered by thin ice, but below that layer, the liquid water continued to boil, with bubbles breaking through or deforming the ice layer. It allowed water to effuse or escape through cracks onto the ice surface.
Dr Frances Butcher, Research Fellow in the School of Geography and Planning at the University of Sheffield and one of the study’s authors, said: “The ice layer that forms is weak and full of holes and bubbles. Our experiments show that as the water boils, the gas that is released gets trapped under the icy crust.”
“Pressure builds, the ice cracks, the gas escapes, and liquid water can briefly seep through the cracks onto the surface of the ice – only to be exposed again to the low-pressure environment,” he said, adding, “As soon as new fractures appear, water begins to boil again, and the entire process repeats itself.”
Dr Petr Broz, from the Institute of Geophysics at the Czech Academy of Sciences and lead author of the study, said: “We found that the freezing process of water under very low pressure is much more complex than previously thought.”
Unlike on Earth, where water freezes below 0 degrees Celsius and boils at 100 degrees Celsius, “water rapidly boils even at low temperatures, as it is not stable under low pressure,” Broz said.
The process the scientists observed of bubbles rising up and deforming the ice cap resulted in an uneven ice crust with bumps and depressions, said the release about the research, funded by the Czech Science Foundation.
Manish Patel, Professor of Planetary Science at the Open University, who supervises the Mars simulation facility, said: “These topographic irregularities – caused by trapped vapour beneath the ice – may leave distinct signatures that could be detectable by orbiting spacecraft, for example by those equipped with radars, offering a potential new way to identify ancient cryovolcanic activity.
“This could provide valuable clues for planning future missions to these remote worlds—and help us better understand the still mysterious process of cryovolcanism.”
