14 DAY TRIAL // The Cassini spacecraft is scheduled tomorrow for a unique fly-by around Saturn's moon Enceladus, to probe in detail the nature of the water plume originating from geysers on the surface in regions around the south pole of the moon. During the fly-by, Cassini will reach an altitude of only 50 kilometers above the surface, while the plume can extend as much as 200 kilometers into space. In the outcome of the discovery of water emerging from Enceladus, planetary astronomers started theorizing about the possibility of the existence of liquid water or even an ocean of water under the frozen surface of the moon.
Although Cassini may find itself in a field of debris impacting it at high speed, this possibility is rather small as previous investigation showed that the particles in the plume are small, thus present no threat of damage to the probe. Since it entered orbit around Saturn in the middle of 2004, Cassini has been routinely traveling through areas of space containing dust-sized particles.
Don't expect any spectacular images though, as the camera will only spring into action when Cassini exits the fly-by. The spectral analyzers will have the main seat in this mission, in order to determine the chemical composition of the plumes. Also, this particular fly-by provides Cassini with the unique opportunity to take pictures and map the northern regions of the moon.
Sascha Kempt, deputy principal investigator for Cassini's Cosmic Dust Analyzer at the Max Planck Institute for Nuclear Physics in Heidelberg, stated: "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".
The water plumes ejected from Enceladus' surface have been discovered by Cassini back in 2005 and were shown to extend into space more than three times the diameter of the moon. Measuring only 500 kilometers in size, the small moon quickly became the most scientifically compelling bodies in the solar system. According to measurements made by Cassini, particles inside the plume are comparable in size to a human hair, and may exceed speeds of 400 meters per second. Additionally, the ejected material creating a large halo around the planet was shown to interact routinely with Saturn's E-ring, which is provided with fresh material in the process.
Aside water, the envelope plume may also contain certain concentrations of carbon dioxide, methane and ammonia or carbon monoxide and nitrogen.
Cassini is scheduled to execute another three fly-bys around Enceladus in the course of this year, with the first one taking place in August. On the 1st of June, Cassini celebrates four years since it has been in orbit around Saturn, thus completing the main objective of the mission. Nonetheless, there is no clear indication that the exploration mission will be abandoned, on the contrary, it will most likely be extended for a few more years.