As NASA's Cassini spacecraft nears the end of its mission observing Saturn's moon Enceladus, scientists are detailing its most compelling findings.

In late Oct., Cassini made its closest approach to Enceladus by flying though one of the moon's icy vapor plume. At the American Geophysical Union conference in San Francisco, project scientists revealed the results from the flyby indicated Enceladus' subsurface ocean has water showing signs of interacting with rock.

"This is remarkably high pH solution," Christopher Glein, a geochemist at the University of Toronto and the Southwest Research Institute in Boulder, Colo., told reporters at the conference, according to Discovery News. "How did it get that way? We think that what happened on Enceladus, and which could still be happening today, is that there were geochemical reactions between magnesium and iron-rich rocks in Enceladus' core reacting with ocean water. Those reactions led to the high pH."

Cassini's next directive will be to flyby Enceladus at a distance of about 3,106 miles on Dec. 19. The spacecraft will continue to orbit the moon until it runs out of fuel in 2017, though it will be from a more considerable distance.

"Understanding how much warmth Enceladus has in its heart provides insight into its remarkable geologic activity, and that makes this last close flyby a fantastic scientific opportunity," Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, said in a news release. "Cassini's legacy of discoveries in the Saturn system is profound.

"We won't get this close to Enceladus again with Cassini, but our travels have opened a path to the exploration of this and other ocean worlds."