Cassini Spacecraft to Dive Into Water Plume of Saturn Moon

March 10, 2008
Enceladus
Cassini space probe mosaic image shows Saturn's moon Enceladus in 2006.

NASA's Cassini spacecraft will make an unprecedented "in your face" flyby of Saturn's moon Enceladus on Wed., March 12.

The spacecraft, orchestrating its closest approach to date, will skirt along the edges of huge Old-Faithful-like geysers erupting from giant fractures on the south pole of Enceladus. Cassini will sample scientifically valuable water-ice, dust and gas in the plume.

The source of the geysers is of great interest to scientists who think liquid water, perhaps even an ocean, may exist in the area. While flying through the edge of the plumes, Cassini will be approximately 120 miles from the surface. At closest approach to Enceladus, Cassini will be only 30 miles from the moon.

"This daring flyby requires exquisite technical finesse, but it has the potential to revolutionize our knowledge of the geysers of Enceladus. The Cassini mission team is eager to see the scientific results, and so am I," said Alan Stern, associate administrator of NASA's Science Mission Directorate, Washington.

Scientists and mission personnel studying the anatomy of the plumes have found that flying at these close distances poses little threat to Cassini because, despite the high speed of Cassini, the plume particles are small. The spacecraft routinely crosses regions made up of dust-size particles in its orbit around Saturn.

Cassini's cameras will take a back seat on this flyby as the main focus turns to the spacecraft's particle analyzers that will study the composition of the plumes. The cameras will image Enceladus on the way in and out, between the observations of the particle analyzers.

Images will reveal northern regions of the moon previously not captured by Cassini. The analyzers will "sniff and taste" the plume. Information on the density, size, composition and speed of the gas and the particles will be collected.

"There are two types of particles coming from Enceladus, one pure water-ice, the other water-ice mixed with other stuff," said Sascha Kempf, deputy principal investigator for Cassini's Cosmic Dust Analyzer at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. "We think the clean water-ice particles are being bounced off the surface and the dirty water-ice particles are coming from inside the moon. This flyby will show us whether this concept is right or wrong."

In 2005, Cassini's multiple instruments discovered that this icy outpost is gushing water vapor geysers out to a distance of three times the radius of Enceladus. The moon is only 310 miles in diameter, but despite its petite size, its one of the most scientifically compelling bodies in our solar system. The icy water particles are roughly one ten-thousandth of an inch, or about the width of a human hair. The particles and gas escape the surface at jet speed at approximately 800 miles per hour. The eruptions appear to be continuous, refreshing the surface and generating an enormous halo of fine ice dust around Enceladus, which supplies material to one of Saturn's rings, the E-ring.

Several gases, including water vapor, carbon dioxide, methane, perhaps a little ammonia and either carbon monoxide or nitrogen gas make up the gaseous envelope of the plume.

"We want to know if there is a difference in composition of gases coming from the plume versus the material surrounding the moon. This may help answer the question of how the plume formed," said Hunter Waite, principal investigator for Cassini's Ion and Neutral Mass Spectrometer at the Southwest Research Institute, San Antonio.

This is the first of four Cassini flybys of Enceladus this year. In June, Cassini completes its prime mission, a four-year tour of Saturn. Cassini's next flyby of Enceladus is planned for August, well into Cassini's proposed extended mission. Cassini will perform seven Enceladus flybys in its extended mission. If this encounter proves safe, future passes may bring the spacecraft even closer than this one. How close Cassini will be allowed to approach will be determined based on data from this flyby.

Source: NASA

Explore further: Cassini looks on as solstice arrives at Saturn

Related Stories

Cassini looks on as solstice arrives at Saturn

May 25, 2017

NASA's Cassini spacecraft still has a few months to go before it completes its mission in September, but the veteran Saturn explorer reaches a new milestone today. Saturn's solstice—that is, the longest day of summer in ...

Cassini finds Saturn's moon Enceladus may have tipped over

May 30, 2017

Saturn's icy, ocean-bearing moon Enceladus may have tipped over in the distant past, according to recent research from NASA's Cassini mission. Researchers with the mission found evidence that the moon's spin axis—the line ...

Cassini mission prepares for 'grand finale' at Saturn

April 4, 2017

NASA's Cassini spacecraft, in orbit around Saturn since 2004, is about to begin the final chapter of its remarkable story. On Wednesday, April 26, the spacecraft will make the first in a series of dives through the 1,500-mile-wide ...

Image: North pole of Enceladus

May 4, 2017

In the north, Enceladus' surface appears to be about as old as any in the solar system. The south, however, is an entirely different story.

Recommended for you

Dutch astronomers discover recipe to make cosmic glycerol

June 23, 2017

A team of laboratory astrophysicists from Leiden University (the Netherlands) managed to make glycerol under conditions comparable to those in dark interstellar clouds. They allowed carbon monoxide ice to react with hydrogen ...

Scientists uncover origins of the Sun's swirling spicules

June 22, 2017

At any given moment, as many as 10 million wild jets of solar material burst from the sun's surface. They erupt as fast as 60 miles per second, and can reach lengths of 6,000 miles before collapsing. These are spicules, and ...

3 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

zevkirsh
not rated yet Mar 10, 2008
um...couldn't the ice damage the sattelite?! why risk it?!
zbarlici
not rated yet Mar 10, 2008
why risk it?!... come on man. Thats the freaking reason they designed the sattelite with particle analysers. Thats a silly question.
weewilly
not rated yet Mar 11, 2008
"To search out new life, to go where no man has gone before." To discover the unknown and if we did not do that in the past we might be all a little crowded in our caves.

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.