Cassini Pinpoints Hot Sources of Jets on Enceladus

Oct 10, 2007
Cassini Pinpoints Hot Sources of Jets on Enceladus
Jets rising from Enceladus, seen in false color. This false-color mosaic shows the entire hemisphere of Iapetus. Image credit: NASA/JPL/Space Science Institute

A recent analysis of images from NASA's Cassini spacecraft provides conclusive evidence that the jets of fine, icy particles spraying from Saturn's moon Enceladus originate from the hottest spots on the moon's "tiger stripe" fractures that straddle the moon's south polar region.

Members of Cassini's imaging team used two years' worth of pictures of the geologically active moon to locate the sources of the most prominent jets spouting from the moon's surface. They then compared these surface source locations to hot spots detected by Cassini on Enceladus in 2005. The new results are published in the Oct. 11, 2007, issue of the journal Nature.

The researchers found that all of the jets appear to come from the four prominent tiger stripe fractures in the moon's active south polar region and, in almost every case, in the hottest areas detected by Cassini's composite and infrared spectrometer.

"This is the first time the visible jets have been tied directly to the tiger stripes," said Joseph Spitale, an imaging team associate and lead author of the Nature paper. Spitale works with Cassini imaging team leader and co-author Carolyn Porco, at the Space Science Institute in Boulder, Colo.

Imaging scientists suspected the individual jets, which collectively feed a plume that towers thousands of kilometers, or miles, above the moon, had been coming from the tiger stripes since the first images of the jets were taken in 2005. But this work provides the first conclusive proof of that hypothesis and provides the first direct evidence of a causal connection between the jets and the unusual heat radiating from the fractures.

To identify the jets' surface locations with certainty, the researchers carefully measured the apparent position and orientation of each jet as observed along the moon's edge by the spacecraft. By making measurements taken from a variety of viewing directions, they were able to pinpoint the jets' sources.

What Spitale and Porco found was intriguing: all measured jets fell on a fracture, but not all jets fell on a previously discovered hot spot. They conclude there are other hot spots to be found. "Some of our sources occur in regions not yet observed by Cassini's composite infrared spectrometer," said Spitale. "So we are predicting that future Cassini observations of those locations will find elevated temperatures."

The scientists also report the suggestion that the characteristics of the jets may depend on tidal frictional heating within the fractures and its variation over a full Enceladus orbit around Saturn. However, more work remains in investigating this issue.

The possibility, first suggested by the imaging team, that the jets may erupt from pockets of liquid water, together with the unusually warm temperatures and the organic material detected by Cassini in the vapor accompanying the icy particles, immediately shoved this small Saturnian moon into the spotlight as a potential solar system habitable zone.

But what actually lies beneath the surface to power the jets remains a mystery.

"These are findings with tremendously exciting implications and to say that I am eager to get to the bottom of it would be a cosmic understatement," said Porco. "Do the jets derive from near-surface liquid water or not? And if not, then how far down is the liquid water that we all suspect resides within this moon? Personally, I'd like to know the answer yesterday!"

The next opportunity for answering these questions will be when Cassini dips low over Enceladus and flies through the plumes in March 2008, obtaining additional data about its chemical composition and the nature of its jets.

A newly processed Cassini image of the jets, and a map of the south polar region showing the correlations between jets and hot spots, can be found at saturn.jpl.nasa.gov

Source: Space Science Institute

Explore further: Boldly going into space for 1,000 days presents a series of health risks

Related Stories

Cassini zooms past Dione

Jun 19, 2015

The rugged landscape of Saturn's fracture-faced moon Dione is revealed in images sent back by NASA's Cassini spacecraft from its latest flyby. Cassini buzzed past Dione on June 16, coming within 321 miles ...

UK amateur recreates the Great Red Spot's glory days

Jun 15, 2015

Maybe it's too soon for a pity party, but the profound changes in the size and prominence of Jupiter's Great Red Spot (GRS) in the past 100 years has me worried. After Saturn's rings, Jupiter's big bloody ...

NASA image: Tethys 'eyes' Saturn

Jun 15, 2015

The two large craters on Tethys, near the line where day fades to night, almost resemble two giant eyes observing Saturn.

Saturn Moon's Activity Could Be 'Curtain Eruptions'

May 06, 2015

New research using data from NASA's Cassini mission suggests most of the eruptions from Saturn's moon Enceladus might be diffuse curtains rather than discrete jets. Many features that appear to be individual ...

Recommended for you

Why we need to keep adding leap seconds

41 minutes ago

Today at precisely 10am Australian Eastern Standard time, something chronologically peculiar will take place: there'll be an extra second between 09:59:59 and 10:00:00.

Helping Europe prepare for asteroid risk

1 hour ago

Each year, astronomers worldwide discover over 1000 new asteroids or other space rocks that could strike our planet. And if one is spotted heading towards Earth, experts working in ESA and national emergency ...

Image: Increasingly active Comet 67P

1 hour ago

On 13 August 2015, Comet 67P/Churyumov–Gerasimenko will reach its closest point to the Sun along its 6.5-year long orbit. It will be around 185 million km from the Sun at 'perihelion', between the orbits ...

Image: Modeling Gaia's avionics on the ground

1 hour ago

A full-size working model of Gaia's internal systems arrived in Germany this week. The Avionics Model is mounted in a circular set-up representing the systems on the actual satellite, now orbiting the Sun–Earth ...

Video: Preparing the ExoMars spacecraft for 2016 launch

1 hour ago

The ExoMars spacecraft is almost complete. A joint mission between ESA and Roscosmos, it begins with the launch of the ExoMars orbiter in 2016 and carries an aerodynamically designed capsule containing a robotic lander. Getting ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.