The discovery of a new form of ice could lead to an improved understanding of our planet’s geology, potentially helping to unlock new solutions in the production, transportation and storage of energy.
Ice XVI, the least dense of all known forms of ice, has a symmetric cage-like structure that can trap gaseous molecules to form compounds known as clathrates or gas hydrates.
Such clathrates are now known to store enormous quantities of methane and other gases in the permafrost as well as in vast sediment layers hundreds of meters deep at the bottom of the ocean floor.
In a paper published in “Nature”, scientists from the University of Göttingen and the Institut Laue Langevin (ILL) report on the first empty clathrate of this type, consisting of a framework of water molecules with all guest molecules removed. Such research could help ease the flow of gas and oil through pipelines in low temperature environments, and open up untapped reservoirs of natural gas on the ocean floor.
Ice XVI is the 17th discovered form of ice, and is the least dense of all known crystalline forms of water. It is also predicted to be a stable low-temperature configuration of water at negative pressures (the equivalent of tension – the opposite of compressive positive pressures), and is so far the only experimentally obtained form of ice to have a clathrate configuration.
According to the 2007 World Energy Outlook, the total amount of methane stored within clathrates on the ocean floor far exceeds the economically exploitable reserves of “conventional” carbon in the form of coal, petrol or natural gas left on Earth.
“It is important to note that clathrates could also be formed with carbon dioxide gas, which would create stable compounds on the ocean floor,” said Thomas Hansen, one of the study authors at the ILL. “This means there is a possibility we could extract methane and convert it to useful energy, and replace it with the CO2. In other words, we could pump CO2 down to the ocean floor as a replacement for the methane in the gas hydrates. The challenges involved would naturally be large and the feasibility has been called into question, but it remains an extremely intriguing possibility worth exploring.”