Cassini samples an alien ocean
Source: By Carolyn Gramling, Science. Also NASA, Cassini.
2015-10-30. Cassini samples an alien ocean. For GSS A Changing Cosmos chapter 7. Excerpt: NASA’s Cassini spacecraft has just sent back the first pictures from its deep plunge toward the surface of icy Enceladus, a flyby that took it through one of the moon’s geysers. ...Since Cassini began its flybys of Saturn and its moons in 2005, scientists have learned that beneath the layer of ice is a global ocean about 10 kilometers thick that may harbor life and probably contains hydrothermal vents. They have spotted more than 100 huge geysers of ice particles, water vapor, and organic molecules spewing from fractures in the ice covering Enceladus’s south polar region. These plumes shoot the contents of the moon’s subglacial ocean hundreds of kilometers high, in eruptions that may resemble curtains rather than columns. This week, the spacecraft made its deepest dive into one such plume—just 49 kilometers above the moon’s surface—to sample its contents.... See also: 2015 Mar 11 Cassini News Spacecraft Data Suggest Saturn Moon's Ocean May Harbor Hydrothermal Activity: "Hydrothermal activity occurs when seawater infiltrates and reacts with a rocky crust and emerges as a heated, mineral-laden solution, a natural occurrence in Earth's oceans. According to two science papers, the results are the first clear indications an icy moon may have similar ongoing active processes. The first paper, published this week in the journal Nature, relates to microscopic grains of rock detected by Cassini.... An extensive, four-year analysis of data from the spacecraft, ...led researchers to the conclusion the tiny grains most likely form when hot water containing dissolved minerals from the moon's rocky interior travels upward, coming into contact with cooler water. Temperatures required for the interactions that produce the tiny rock grains would be at least 194 degrees Fahrenheit (90 degrees Celsius)...."