NASA says its Cassini spacecraft has successfully completed another flyby of Saturn's moon Enceladus and is sending data from the event back to Earth.

Astronomers said Cassini has approached Enceladus more closely, but Monday's passage took the spacecraft on its deepest plunge yet through the heart of the plume being emitted from the moon's south polar region.

At its closest point Monday, Cassini flew about 60 miles above the surface of Enceladus, officials said.

"Since the discovery of the plume in 2005, scientists have been captivated by the enigmatic jets," NASA said in a statement. "Previous flybys detected water vapor, sodium and organic molecules, but scientists need to know more about the plume's composition and density to characterize the source, possibly a liquid ocean under the moon's icy surface. It would also help them determine whether Enceladus has the conditions necessary for life."

Space agency mission managers said they conducted extensive research before the flyby to make sure the spacecraft could fly safely through the plume and not use an excessive amount of propellant.

Cassini was launched Oct. 15, 1997, and entered into orbit around Saturn July 1, 2004.