Space Science Institute via Associated Press, NASA/JPL-Caltech
This July 27, 2015 photo made by the Cassini spacecraft shows the moon Enceladus orbiting the planet Saturn. To the north, top, the terrain is covered in impact craters, much like other icy moons, but to the south, the record of impact cratering is much more sparse, and instead the land is covered in fractures and long, linear features. The image was taken in visible green light at a distance of approximately 70,000 miles (112,000 kilometers) from Enceladus. On Wednesday, Oct. 28, 2015, Cassini will travel through a jet of water vapor and frozen particles erupting from the moon's south pole providing the best sampling yet of its underground ocean.

CAPE CANAVERAL, Fla. — The Cassini spacecraft is about to get an icy shower as it orbits Saturn.

On Wednesday, Cassini will storm through a jet of water vapor and frozen particles erupting from the south pole of Enceladus, one of Saturn's many moons. The spacecraft will zoom within 30 miles of the moon's south pole, providing the best sampling yet of its underground ocean.

Cassini will be traveling 19,000 mph, so it should take an instant to penetrate the plume.

A global liquid ocean is believed to exist beneath the frozen crust of 300-mile-wide Enceladus. Wednesday's dive will be the deepest one yet through one of its plumes.

Launched in 1997, Cassini isn't equipped to detect life. But scientists hope Wednesday's flyby will shed light on the potential habitability of Enceladus' ocean.