Enceladus_craters_and_complex_fractured_terrainsYesterday, the space probe Cassini, which was launched in 1997, and has been studying Saturn and its moons since it arrived at the ringed planet in 2004, conducted one last flyby of the moon Enceladus (pictured).

Previous investigation of the moon by the probe (which is a joint project of NASA and the European and Italian Space Agencies) has revealed the presence of a subsurface ocean which is sandwiched between the moon’s rocky core and ice-crusted surface. In addition, plumes of ice water have been detected shooting into space from the moon’s south pole.

The findings are of interest to scientists for more than just geological reasons. As was discussed in an article on exoplanets and extra-terrestrial life in our Dec. 10 issue, the presence of liquid water in the moon’s interior makes it one of the few candidates in the solar system outside of Earth to possibly harbour life.

As our article notes, liquid water is only one prerequisite. You also need organic compounds (carbon being the key) and an energy source.

Carbon is extremely common in our solar system/galaxy. As for an energy source, on Enceladus that would likely take the form of underground volcanic vents. On Earth, they have been found to support life at great depths on the ocean floor. With a previous flyby of Enceladus in October, Cassini sampled the plumes at the moon’s south pole. Yesterday, it passed within 5000 km of the surface to try to measure the level of heat in the moon’s interior to determine if volcanic-style vents or some other geological heat source might be present.

With the flyby complete, Cassini will now turn its attention to studying Saturn’s rings for the next 20 months. In September 2017, the probe is scheduled to enter Saturn’s atmosphere and cease functioning.