A new study has found that potential visitors to the ocean floor can receive vital nutrients from the molten parts of their planets through the thick layers of high-salt ice that can carry salt.
Water is one of the most common molecules in the universe, and the Earth that is covered by Earth’s oceans hundreds of miles in depth may be higher than “dry” planets like Earth. Examples of such waters include several planets in the TRAPPIST-1 system, as well as GJ 1214b, Kepler-62e, and Kepler-62f.
The conditions at the bottom of the oceans are so extreme that the water is mixed enough to form high-pressure ice called ice VII. Atoms of ice VII are arranged in the cubic crystalline structure. They exist under pressures more significant than three gigapascals (approximately 29,000 atmospheres) and temperatures of up to 662 degrees Fahrenheit (350 degrees Celsius).
However, scientists were unsure whether the salt and other nutrients could escape from the rocky terrain, pass through the ice VII mantle, enter the ocean floor – and then return to the bottom again. Regular ice releases salt when solid, but new models show that ice VII can retain salt crystals. In particular, studies have shown that ice VII can contain up to 2.5 wt% (percentage of weight) of sodium chloride, more commonly known as table salt. The presence of salt reduces the rate at which ice melts, immerses it, and thus helps the flow of hot water to cause the salty ice to rise.
“The transport of salt was not only from bottom to top, but also from top to bottom,” said Jean-Alexis Hernandez, a scientist at the European Synchrotron Radiation Facility in France. “The hot ice under the blanket is unstable because, as it is hot, it is much smaller than the surrounding ice, which causes it to rise. Global flow is improving and maintaining the temperature difference between the top and bottom of the blanket,” Hernandez told Space.com.
This flow restores the nutrients and salts needed for biochemistry. Although their presence does not guarantee life in the oceans, it does increase the likelihood that such a world would be uninhabited.