Saturn Enceladus

Saturn's moon Enceladus, nearly 900 million miles away from Earth, is NASA's next candidate as an incubator for alien life, according to a newly published study. The agency on Thursday concluded that the moon might possibly harbor an underground ocean of liquid water, suggesting the icy rock is has an environment suitable for extraterrestrial microbes.

The fresh evidence was discovered by NASA's Cassini and Deep Space Network, confirming early research that theorized Enceladus had an interior reservoir of water all the back in 2005. The early theory came from an observation from Cassini that saw water vapor and water ice plumes near the moon's south pole. That phenomena isn't unlike what's been observed on Jupiter's moon Europa.

Researchers said the ocean on Enceladus is in the region of six miles deep, and lies beneath the moon's shell of ice, which is about 19 to 25 miles thick. But the part that makes the potential discovery even more exciting is that the water is in direct contact with a rocky seafloor, making all kinds of chemical reactions possible. The moon itself is about 300 miles in diameter, and researchers hadn't considered Enceladus as a candidate for life until Cassini reached Saturn back in 2004.

Scientists were able to take measurements of Enceladus using Cassini, which has flown near the Saturn moon 19 times, three of which took place from 2010-2012. "The way we deduce gravity variations is a concept in physics called the Doppler Effect, the same principle used with a speed-measuring radar gun," Samir Asmar of NASA's Jet Propulsion Laboratory in Pasadena, Calif. explained. "As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we're trying to measure."

NASA then measured the change in velocity as a change in radio frequency, which is pinged all the way back to the agency's Deep Space Network here on Earth. Using this technique, NASA is able to detect changes in velocity as small as less than one foot per hour, the agency said; the evidence turned back results suggesting Enceladus's south pole had a higher density than other portions of the interior. If true, the salty contents of the water could suggest Enceladus has an environment suitable for life.

"This new validation that an ocean of water underlies the jets furthers understanding about this intriguing environment," said Linda Spilker, Cassini's project scientist at JPL.