Washington, March 11 : NASA's Cassini spacecraft will make an unprecedented flyby of Saturn's moon Enceladus on March 12, where it will skirt along the edges of huge geysers erupting from giant fractures on the south pole of the moon.
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 particles and gas escape the surface at jet speed at approximately 800 miles per hour.
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.
Cassini will sample scientifically valuable water-ice, dust and gas in the plume.
"This daring flyby requires exquisite technical finesse, but it has the potential to revolutionize our knowledge of the geysers of Enceladus," said Alan Stern, associate administrator of NASA's Science Mission Directorate, Washington.
Cassini's cameras will take a back seat on this flyby as the main focus will turn 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. Information on the density, size, composition and speed of the gas and the particles will also be collected.
According to Sascha Kempf, deputy principal investigator for Cassini's Cosmic Dust Analyzer at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, "There are two types of particles coming from Enceladus, one pure water-ice, the other water-ice mixed with other stuff."
"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," he added.
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.