The spacecraft will fly at about 50 kilometers (30 miles) above the surface of Enceladus.


JOHN SPENCER: Enceladus is an amazing place. It's one of the most remarkable places we've found in the Saturn system. It's got these fractures that are spouting water vapor and ice, these enormous plumes coming out of the south pole.

The geysers on Enceladus are actually quite a lot like Old Faithful geyser or other geysers in Yellowstone National Park that we are familiar with. In fact, the total amount of material coming out of Old Faithful in one of its eruptions is similar to the amount of material that comes out of the geysers on Enceladus.

MARCIA BURTON: Obviously, there's a source of water down there. It's coming out everywhere. So, how big it is, how extensive, people don't know for sure.

SPENCER: Because it's so much colder, we don't get liquid water coming out of those geysers, we get a lot of very fine ice particles, a lot of vapor.

BOB MITCHELL: For this flyby, we're coming down from the north, going past the equator and down under the south pole.

The Shuttle, in orbit around the Earth, is at about 300 kilometers up. We're going to be about six times closer than that. The closest approach point is just a little below the equator. But, by the time we get down near the South Pole, where the plumes are, we're going to be up more like 200 kilometers altitude.

SPENCER: We just sort of grazed the edge of the plume last time in -- in 2005. This time we're really plunging into the plume.

BURTON: The measurements made by the instruments will certainly lead to understanding the interior, how extensive the water source is, what processes are forming those geysers.

SPENCER: We'll really be tasting the plume, taking the material from the plume into the instruments onboard the spacecraft and analyzing them.

MITCHELL: How risky is it to be flying through this part of the plumes? The particles are very small -- micron-sized particles. None of the big particles can get lofted by the plumes to be as high as we're going to be.

So, the scientists are repeatedly assuring us that environment is just not a threat.

View all Videos