How NASA's Cassini Saturn mission found a new target in the search for habitable worlds beyond Earth

February 17, 2017 by Preston Dyches
A dramatic plume sprays water ice and vapor from the south polar region of Saturn's moon Enceladus. Cassini's first hint of this plume came during the spacecraft's first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL/Space Science Institute

On Feb. 17, 2005, NASA's Cassini spacecraft was making the first-ever close pass over Saturn's moon Enceladus as it worked through its detailed survey of the planet's icy satellites. Exciting, to be sure, just for the thrill of exploration. But then Cassini's magnetometer instrument noticed something odd.

Since NASA's two Voyager spacecraft made their distant flybys of Enceladus about 20 years prior, scientists had anticipated the little moon would be an interesting place to visit with Cassini. Enceladus is bright white—the most reflective object in the solar system, in fact—and it orbits in the middle of a faint ring of dust-sized ice particles known as Saturn's E ring. Scientists speculated ice dust was being kicked off its surface somehow. But they presumed it would be, essentially, a dead, airless ball of ice.

What Cassini saw didn't look like a frozen, airless body. Instead, it looked something like a comet that was actively emitting gas. The magnetometer detected that Saturn's magnetic field, which envelops Enceladus, was perturbed above the moon's in a way that didn't make sense for an inactive world. Could it be that the moon was actively replenishing gases it was breathing into space?

Thus began a hunt for clues that has turned out to be Cassini's most riveting detective story. "Enceladus was so exciting that, instead of just three close flybys planned for our four-year primary mission, we added 20 more, including seven that went right through the geysers at the south pole," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California.

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Credit: Jet Propulsion Laboratory

By following the trail of scientific breadcrumbs, Cassini eventually found that Enceladus harbors a global ocean of salty water under its icy crust, possibly with hydrothermal vents on its seafloor. The trail of clues that began with a puzzling magnetometer reading led to an understanding that the moon—and perhaps many small, icy moons like it throughout the cosmos—could potentially have the ingredients needed for life.

"Half the excitement of doing science is that you sometimes find yourself going in a totally different direction than you expected, which can lead to amazing discoveries," said Spilker. "That little anomaly in Cassini's magnetometer signal was unusual enough that it eventually led us to an ocean world."

Launched in 1997, the Cassini mission is currently in its final year of operations, performing weekly ring-grazing dives just past the outer edge of Saturn's rings. In April, the spacecraft will begin its Grand Finale, plunging through the gap between the rings and the planet itself, leading up to a final plunge into Saturn on September 15.

Cassini has been touring the Saturn system since arriving in 2004 for an up-close study of the planet, its rings and moons, and its vast magnetosphere. Cassini has made numerous dramatic discoveries, besides the activity at Enceladus, including liquid methane seas on another moon, Titan.

Explore further: Cassini transmits first images from new orbit

More information: For a timeline of Cassini's Enceladus discoveries, visit go.nasa.gov/2k0CRP3

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7 comments

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Da Schneib
5 / 5 (8) Feb 18, 2017
Why we spend money on seemingly useless scientific pursuits.

The thing about doing science is you *always* find out *something*.
Edenlegaia
not rated yet Feb 18, 2017
Why we spend money on seemingly useless scientific pursuits.

The thing about doing science is you *always* find out *something*.


They search. They find either what they expected, something they didn't, or nothing at all. And that's also a result you can interpret in a way you couldn't before searching. Easy as that.
And something tells me they're better at doing anything regarding science than you. Call it intuition, i can't spend money on a seemingly useless way to prove i'm right.
gkam
1.8 / 5 (5) Feb 18, 2017
Yeah, but the next mission looking for life on moons, will go to Europa, a mistake in my opinion.
cantdrive85
1 / 5 (5) Feb 19, 2017
Instead, it looked something like a comet that was actively emitting gas. The magnetometer detected that Saturn's magnetic field, which envelops Enceladus, was perturbed above the moon's south pole in a way that didn't make sense for an inactive world.

What they found is an electric current system, but due to ignorance it led to erroneous conjecture;
Cassini eventually found that Enceladus harbors a global ocean of salty water under its icy crust, possibly with hydrothermal vents on its seafloor.

Such is the case when those who are charged with the evaluation of the evidence have an empty toolkit, plumbers trying to describe the physics of a complex circuit, for example.
The evidence has pointed them in the right direction;
https://www.nasa....069.html
...but then they arrive at the ocean nonsense ILO a description that acknowledges that the flow of these charged particles actually "do something", like creating a plasma gun.
baudrunner
5 / 5 (5) Feb 19, 2017
And something tells me they're better at doing anything regarding science than you.
What was that for? Something tells me that your reading comprehension skills are sorely lacking. Da Schneib was saying that in the end something rewarding will always reveal itself out of the effort of pursuing what at onset might appear to be a 'seemingly useless' endeavor.

Whydening Gyre
not rated yet Feb 19, 2017
The magnetometer detected that Saturn's magnetic field, which envelops Enceladus, was perturbed above the moon's south pole in a way that didn't make sense for an inactive world.

What they found is an electric current system, but due to ignorance it led to erroneous conjecture;

What they FOUND is gravity actively interacting enough with a certain chemistry, to create a magnetic field, interacting with Saturn's magnetic field, generating an electric field. Which then enhances the magnetic component. And so on...
... found that Enceladus harbors a global ocean of salty water under its icy crust, possibly with hydrothermal vents on its seafloor.

Such is the case when those who are charged with the evaluation of the evidence have an empty toolkit, plumbers trying to describe the physics of a complex circuit, for example.

You over-simplify plumbing. It's all about flow (just like electricity)
Such is the case of arm-chair quarterbacks.
cantdrive85
1 / 5 (1) Feb 20, 2017
What they FOUND is gravity actively interacting enough with a certain chemistry, to create a magnetic field,

Stick to the art there WG. What would you call that? Gravitochemistry? Laughably laughable!

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