The NASA/ESA/ASI Cassini spacecraft will make a daring approach within just 30 kilometres of Saturns moon Enceladus, before flying through a plume of steam emanating from its south pole.
London, Aug 2 : The NASA/ESA/ASI Cassini spacecraft will make a daring approach within just 30 kilometres of Saturn's moon Enceladus, before flying through a plume of steam emanating from its south pole.
The team of international astronomers involved in the Cassini project say the aim of this exceptionally close encounter is to find out what is powering that plume.
A dozen or so jets appear to be blasting water vapour and ice crystals out of fissures near the south pole.
The activity has befuddled scientists, as small ice moons such as Enceladus, usually don't have such volcanic activity.
"How can a body only 500 km in size have enough internal heat to drive a spewing plume of water into space to distances much greater than its own size?" said James Green, director of NASA's Planetary Division.
Astronomers are now of the opinion that the heat must have something to do with the fact that Saturn's gravity squeezes the moon, though they are still unsure why the heat is focused at the south pole, or whether it is piped into hot-water geysers like those on Earth, or whether it merely warms up surface ice, making it evaporate.
But there are risks involved. The Cassini spacecraft was originally scheduled to pass by Enceladus in March 2008 at a distance of around 1000 kilometres, and the ice crystals in the plume could damage the spacecraft's sensitive optics.
Astronomers are now planning to skim close to the equator of Enceladus heading south. Then Cassini's instruments can be pointed at the south pole while being shielded from plume particles by the body of the spacecraft.
As well as giving the cameras a closer look at the fissures to see where the jets of steam are actually coming from, this manoeuvre will allow Cassini's onboard chemical analyser a chance to taste the plume. It will find out whether the water is tainted with ammonia, methane and other substances.
Scientists believe the chemical makeup could reveal the nature of Enceladus's remarkable plume.
"Cassini was never designed to fly this close. But the people at JPL have really worked this out carefully and believe they can hit the mark within a few kilometres, so we have plenty of margin for error," New Scientist quoted Green as saying.
Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, US, are calculating whether it's safe to go nearer, he said.
ANI