A vanishing act on Saturn's largest moon Titan that forms "magic islands" may be streams of nitrogen bubbles that appear and disappear at random, a new study revealed.
Disappearing Islands
Previous studies have found that some of Titan's large seas and lakes are quite combustible, and they usually appear dark. In 2013, NASA's Cassini orbiter sent back radar images showing mysterious bright anomalies on the surface of Titan's Ligeia Mare sea.
Since then, scientists have wondered what makes these magic islands wink out of existence and re-emerge. Past studies suggested the existence of potential floating solids or gas bubbles. In March 2017, experts revealed seas of Titan may erupt occasionally with patches of bubbles.
Now, a research team has provided scientific evidence that bubbles that contain a mix of ethane, nitrogen, and methane may be to blame for this strange phenomenon.
Experts from France's University of Reims analyzed conditions observed on Titan and concluded that specific temperatures and pressures in the depths of this hydrocarbon sea may destabilize, causing nitrogen bubbles to appear on the surface.
Led by planetary scientist Daniel Cordier, the team developed computer models of how liquids and gases might act in Titan's frigid seas. These computer models were partly based on experimental data previously gathered by the oil and gas industry about how similar fluids behave under pressure in deep underground.
Nitrogen Bubbles
The new study suggests that on Titan, fluids on the surface are richer in methane, while fluids deep underground are richer in ethane. The surface fluids interact with the Saturn moon's nitrogen-rich atmosphere, and as a result, these fluids are also rich in nitrogen.
Factors such as tides, winds, or the effects of cooling and heating may force these surface fluids to flow downward and sink. These mixtures separate because of the pressure at the lowered depths, and the nitrogen bubbles released by these mixtures rise back up to the surface.
Because nitrogen bubbles are reflective to radio waves, they appear bright under radio scans, the study said. These bubbles can reach at least 4.6 centimeters (1.8 inches) in width and can form at depths of about 100 to 200 meters (330 to 660 feet).
Furthermore, the Cassini spacecraft did not directly see the bubbles because the fizzing is only temporary, scientists said.
Cordier said future missions that plan to deploy submarines to the Saturn moon's seas should study these strange characteristics.
"Possible instabilities of the liquid at the sea bottom have to be taken into account," he said.
The findings of the report are published in the journal Nature Astronomy.
