AsianScientist (Oct. 6, 2017) – The secret to life in the low temperatures of space may lie in the unusual behavior of interstellar ice, according to a study using ultraviolet light to study non-crystallized ice. These findings have been published in Science Advances.
Common ice is a crystalline material with orderly bonds and molecular structure. In contrast, interstellar ice behaves differently, displaying liquid-like properties even at extremely low temperatures. How this phenomenon occurs is still unclear.
In this study, a team led by Associate Professor Shogo Tachibana of Hokkaido University in Japan discovered that ultraviolet-irradiated amorphous ice mimics interstellar ice, exhibiting liquid-like behavior at extremely low temperature ranges. The researchers sprayed a mixed gas of water, methanol and ammonia onto a substrate which was chilled to -263°C to -258°C and simultaneously irradiated with ultraviolet light. After the ice formed, the researchers turned off the freezer to observe the ice with a microscope as the temperature rose.
To their surprise, the ice bubbled like boiling water at temperatures between -210°C and -120°C. Analysis of the gas revealed that it consisted of hydrogen molecules, which the researchers believe were formed from methanol and ammonia broken up by UV irradiation. The bubbling showed that the ice was behaving like a liquid, with a viscosity estimated to be similar to that of firm honey.
They then examined the behavior of ice made from pure water. Islands of amorphous, pure water ice were created on a substrate by irradiating crystalline ice with ultraviolet light at -263°C. They observed the islands as the temperature was raised and witnessed the islands of amorphous ice changing shape and spreading over the substrate, indicating that the ice was behaving like a liquid. The estimated viscosity of this ice was similar to that of magma rich in silica. This result implies that the liquid-like state is common even in ice consisting of pure water.
These experiments suggest that real interstellar ice might behave like a liquid, enhancing the formation of organic compounds, including molecules that could give rise to life.
“The formation of organic molecules, including prebiotic ones, may efficiently occur in a very cold environment,” said Tachibana.
“The liquid-like ice may help dust accrete to planets because liquid may act as a glue. However, further experiments are needed to understand the material properties of the liquid-like ice,” he added.
The article can be found at: Tachibana et al. (2017) Liquid-like Behavior of UV-irradiated Interstellar Ice Analog at Low Temperatures.
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Source: Hokkaido University; Photo: Shutterstock.
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