Crystal structure ice that was thought to be "not on the earth" is discovered from diamonds

byJennifer Boyer

By applying a strong pressure to the ice which we usually eat and see, we know that a new type of ice with different structure and nature will be formed. A report that "ice of a structure that was thought to be" not present on the earth "because the pressure necessary for formation is too strong was found from the diamond"ScienceIt is announced in.

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth's deep mantle | Science
http://science.sciencemag.org/content/359/6380/1136

What scientists found trapped in a diamond: a type of ice not known on Earth
http://www.latimes.com/science/sciencenow/la-sci-sn-water-in-diamonds-20180308-story.html

When high pressure is applied to icePhase shiftIt is known that the crystal structure of atoms changes and forms ice of different crystal structure and properties. For example, if oxygen atoms that we normally see areHexagonal formThe type called ice I which is lined up in, changes to oxygen ice II with different arrangement of oxygen atoms when applying strong pressure. It will change to ice XVI at maximum with increasing pressureIt is knownHowever, what was discovered this time is "Ice VIIType. It was thought that ice formed under a very strong pressure like ice 7 does not exist on the earth and can only be made under special conditions like inside the laboratory.

Scientists say "Ice VII" is a satellite's satelliteEnceladusAnd the satellites of JupiterEuropaInside of a star made of ice such as Saturn's satellite with huge oceanTitanI thought that it exists only in the seafloor etc. The pressure required to form ice 7 is very high and it is too hot to make ice, as it is deep in the mantle that can obtain such pressure on the earth is.

However, he is a professor of geology at the University of NevadaOliver TschaunerMr. announced that he found ice VII, which was thought not to exist in the natural world on the earth, on the earth. Mr. Tshauner discovered ice VII in the diamonds.

byChristophe Capeau

The crystal of diamond is made in the mantle which is about 400 m underground (about 650 kilometers), and its crystal rapidly moves near the surface of the earth and it cools down to become a diamond that we see. In the course of its formation, diamond seems to encapsulate substances near the mantle in the crystal like a capsule, and it sometimes cools down together with the contents.

In this way, there are cases where mining is done with contents in the diamond, but the inclusion of the encapsulated diamond is kept in the diamond at the same pressure as the pressure when encapsulated. "Since the lattice structure of diamonds does not relax so much, even when they are deep inside the mantle, even when they are in the hands of man, the pressure and volume on inclusions will hardly change," says Tshauner.

Water molecules near the Earth's mantle are too hot too, so it will not change to ice VII no matter how much pressure is applied. However, when water molecules pressurized are accidentally encapsulated when diamond is formed, and the encapsulated diamond rises rapidly to near the surface of the earth, water molecules inside the diamond are also cooled and crystallized. At that time the internal pressure is the same as in the mantle, so water molecules will crystallize in the state of ice VII, not ice I.

byJonathan Lamb

Tshauner et al.'s research group searched for a new structure of carbon dioxide and was doing X-ray scanning of diamond originally, not searching diamond looking for ice VII. "When we found ice VII by chance during the x-ray scanning process, we were very excited," Tshauner says.

Because it was discovered by this accidental discovery that ice VII was found to exist in the natural world of the earth,International Mineralogical AssociationIt was said that it was registered as a mineral. In this case, "A crystal that seemed not to exist in nature from among diamonds" was discovered, the accidental action that nature brings is likely to be a good example of a phenomenon that scientists sometimes did not expect .