NASA killed Cassini to avoid contaminating Saturn's moons

NASA scientists killed the hard-working Cassini spacecraft to avoid contaminating Saturn's moons with Earth microbes because they may have the potential to support life.

On Friday at 7:55 a.m. ET, the world said goodbye to Cassini after 20 years in space and 13 years orbiting Saturn and its moons, providing incredibly detailed, high-resolution photos of what many consider the jewel of our solar system.

Though Cassini's life was extended twice with new missions, the spacecraft had a limited fuel supply. So NASA announced in April that it would carry out one final mission, dubbed The Grand Finale.

• How Cassini helped us expand the search for life
• Cassini flies between Saturn and rings

Scientists and engineers altered the orbit of the spacecraft to run into Saturn, where it would safely burn up in its atmosphere.

Cassini's fate arose directly from its success in shedding a light on the possibility of life on other worlds. 

On Wednesday, NASA's planetary science division director Jim Green spoke about Enceladus, a small, icy moon, spewing organic material that likely originates from a subsurface ocean.

"What we thought was an icy ball, when we observed the southern hemisphere, and geysers of water spewing out into the Saturn system, it amazed us," he told reporters.

"And it began changing the way we view the habitability or potential habitability of moons in the outer part of our solar system."

Allowing Cassini to run out of fuel would leave NASA no way to control the spacecraft. One day it could crash into Enceladus or even Titan, Saturn's largest moon, which is also being studied for potential habitability.

While there is no guarantee that there is microbial life on any of these moons, there is a chance of contaminating their surface with Earth microbes. 

"Now because of the importance of Enceladus that Cassini has shown us, and of Titan, another potential world that could be habitable for life, perhaps not like we know it, but perhaps completely different than ours, we had to make decisions on how to dispose of the spacecraft," Green said.

"And that led us, inevitably, to the plan of taking Cassini and plunging into Saturn."

On the plus side, Cassini's Grande Finale has given us unprecedented views of the planet's north pole as well as its intricate ring system. For the first time in its mission, the spacecraft flew between the planet and the rings. 

'We might find in fact a higher probability than I'm willing to admit right now that life exists in the interior of Enceladus.'— Larry Soderblom, Cassini scientist

And, with its success and valuable insight into the potential habitability of other worlds, it's likely there could be new missions.

Missions have been suggested to explore Enceladus, including its interior and the subsurface liquid body, Larry Soderblom, an interdisciplinary scientist on the Cassini mission, told CBC News.

"We might find in fact a higher probability than I'm willing to admit right now that life exists in the interior of Enceladus."

While astronomers and planetary enthusiasts may miss the data and photos gathered by Saturn, NASA's Juno spacecraft is also orbiting Jupiter. And there are plans for the Europa Clipper, which will conduct flybys of another icy, potentially habitable moon, Europa.

If there is a chance for life to be found in the Saturn system, NASA is eager to protect it. 

"Because of planetary protection and our desire to go back to Enceladus and go back to Titan and go back to the Saturn system, we must protect those bodies for future exploration," Green said.