Curious ocean phenomenon adds a twist to science

Chinese scientists have found more evidence of the presence of superheated water vapor in a hydrothermal system on the sea floor, according to a recent study published in the journal Geophysical Research Letters.

Deep sea hydrothermal systems are a hot spot in scientific research globally, as they are believed to contain abundant mineral and genetic resources and may be linked to the origin of life on Earth, according to Zhang Xin, one of the paper's authors.

Water vapor at hundreds of degrees Celsius from high-pressure deep sea hydrothermal vents usually cools quickly as it encounters surrounding seawater. But with their remote-controlled submersible vehicle, Faxian, the scientists photographed a special system in which numerous inverted lakes filled with shimmering water at a depth of more than 2,000 meters may prevent cooling.

The images showed mushroom cap structures above a hydrothermal opening in the sea bed, which they believed could impede direct contact between the hot fluids and the ambient seawater.

Using a non-destructive chemical analysis technique, researchers found that liquid trapped in the inverted lake could be divided into three layers. The bottom layer is normal seawater with the lowest temperature and greatest density. In the middle layer, condensation and evaporation of seawater occur simultaneously. The top layer is a superheated vapor, with temperatures as high as 383.3 C.

"The vapor phase is a sort of big underwater bubble. The reason it does not rise is that the mushroom structure caps it like an inverted bowl," Zhang said.

"The shimmering water trapped by the mushroom cap strongly reflected light, which indicates significant temperature and density differences compared with the surrounding seawater," said Zhang, who is a fellow at the Institute of Oceanology of Chinese Academy of Sciences in Qingdao, Shandong province.

Zhang said hydrothermal vents similar to the low-density hydrothermal system they found have also been observed in many other regions, and deserved much more study.